< OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN eiaopv \ 6 A996 DE A5VIT l H' *"» DARD D ECONOMY Q THESIS D ECONOMY ALTTH 1ST D NO VOLS THIS TITLE LEAF ATTACH j COLOR OR TITLE I .D. PLE 20706 ra^gr )IS ISSN BIX IINDING WHEEL SYS. ID. * E Stf CY 1 3 m 1 NEW SERIF Revision of the Tribe Phyllotin (Rodentia: Sigmodontinae), with a Phylogenetic Hypothesis for the Sigmodontinae Scott J. Steppan february 28, 1995 Miblication 1464 >I I UBLISHED BY FIELD MUSEUM Ol i for i n - tffors Ui '■ reduces th ieaiion res.:. n thcre< , • uete copi i copy plus two .'.id Mos-r.ui Ulmoi: . t" and n the nieti w that of r Style (I3ih ; given in '. lvcrsily oi index ot A structure, >ns are rei nford .. lontai md floristics. Journal of ind Si .--.. Bulletin 143, Bui Guatemala tdiana: 1 in the text (not as "pU . ' . ■ ■ ! <■ I ■■{! mpanicd b acceptable : figure; Dens;, ami i), and may not exceed 11V4 obtained in (preferred) it ion; and photo ■ ■■ color corresponding autii can be made and queries ans a be made of) the s . . : ON ACID FREE PAPER. Revision of the Tribe Phyllotini FIELDIANA Zoology NEW SERIES, NO. 80 Revision of the Tribe Phyllotini (Rodentia: Sigmodontinae), with a Phylogenetic Hypothesis for the Sigmodontinae Scott J. Steppan Division of Mammals Field Museum of Natural History Roosevelt Road at Lake Shore Drive Chicago, Illinois 60605-2496 Committee on Evolutionary Biology The University of Chicago Chicago, Illinois 60637 Accepted July 11, 1994 Published February 28, 1995 Publication 1464 PUBLISHED BY FIELD MUSEUM OF NATURAL HISTORY © 1995 Field Museum of Natural History Library of Congress Catalog Card Number: 94-62054 ISSN 0015-0754 PRINTED IN THE UNITED STATES OF AMERICA Table of Contents Abstract 1 Introduction 1 Evolutionary Relationships within Sigmo- dontinae 2 Taxonomic History of the Phyllotines ... 6 Materials and Methods 7 Taxa and Characters Examined 7 Quantitative Character Coding 10 Analytical Methods 11 Comparative Morphology 13 Dentition 14 Cranium and Mandible 26 Postcranial Skeleton 40 External Morphology 49 Characters of the Phallus and Soft Anatomy 51 Phylogenetic Relationships within Sigmo- dontinae 53 Results 53 Discussion 60 Phyllotine Monophyly 62 Phylogenetic Relationships within Phyllotini 63 Results 63 Discussion 70 Taxonomy 72 Acknowledgments 100 Literature Cited 101 Appendix: Specimens Examined 104 List of Illustrations 1 . Albumin immunological dendrogram (from Sarich, 1985) 3 2. Evolutionary scenario for South Ameri- can sigmodontines (from Hershkovitz, 1962) 5 3. Hypothesized relationships of South American "cricetines," based on phallic characters (from Hooper & Musser, 1964) 6 4. Nomenclature for dental elements (from Reig, 1980) 9 5. Phenogram and cladogram from electro- phoretic data (from Spotorno, 1986) .. 10 6. Dorsal view of a generalized Phyllotis cranium 18 7. Ventral view of a generalized Phyllotis cranium 20 8. Lateral view of a generalized Phyllotis cranium 22 9. Variation in incisor grooves among phyllotines 23 10. Variation in upper incisor dentine fis- sures 23 1 1 . Variation in ventromedial process of mandibular ramus 27 12. Position of anterior root of zygomata .. 29 13. Dorsal views of interorbital region .... 31 14. Dorsolateral views of posterior cranium 34 15. Stapedial spine of auditory bulla 35 16. Medial views of auditory bulla and in- ternal carotid canal 36 17. Ventral view of hemal arches and hemal processes in Nectomys squamipes 48 18. Ventral and lateral views of bacular ap- paratus in Phyllotis magister 52 19. Strict consensus cladogram for the Sig- modontinae; analysis weighted to favor sigmodontine monophyly 54 20. Strict consensus cladogram for the Sig- modontinae; unweighted analysis 56 21. Majority-rule bootstrap consensus tree for the Sigmodontinae; analysis weight- ed to favor sigmodontine monophyly . . 58 22. Strict consensus cladogram for the Phyl- lotini 64 23. Eighty percent majority-rule consensus tree, derived from most-parsimonious trees wherein Punomys is not a phyllo- tine 65 24. Majority-rule bootstrap consensus tree for the Phyllotini 66 25. Cranium and mandible of Calomys lau- cha 73 26. Upper and lower molars of Calomys laucha 74 27. Cranium and mandible of Eligmodontia morgani 76 28. Upper and lower molars of Eligmodon- tia morgani and Graomys griseoflavus . 11 29. Cranium and mandible of Graomys gris- eoflavus 78 30. Cranium and mandible of Phyllotis dar- wini 80 3 1 . Upper and lower molars of Phyllotis darwini and Loxodontomys micropus . . 81 32. Cranium and mandible of Loxodonto- mys micropus 83 33. Cranium and mandible of Auliscomys pictus 85 34. Upper and lower molars of Auliscomys pictus and Galenomys garleppi 86 35. Cranium and mandible of Galenomys garleppi 87 36. Cranium and mandible of Chinchillula sahamae 89 37. Upper and lower molars of Chinchillula sahamae and Andinomys edax 90 38. Cranium and mandible of Andinomys edax 92 39. Cranium and mandible of Irenomys tar- salis 93 40. Upper and lower molars of Irenomys tarsalis and Euneomys chinchilloides . . 94 41. Cranium and mandible of Euneomys chinchilloides 96 42. Cranium and mandible of Neotomys ebriosus 97 43. Upper and lower molars of Neotomys ebriosus and Reithrodon auritus 98 44. Cranium and mandible of Reithrodon auritus 99 List of Tables 1 . Species included in sigmodontine analysis 2 2. Species included in phyllotine analysis . . 8 3. Data matrix for the phylogenetic analysis of the Sigmodontinae 12 4. Data matrix for the phylogenetic analysis of the Phyllotini 14 5. Vertebral counts among Neotropical sig- modontines and selected muroids 42 6. Distribution of selected characters among oryzomyine and thomasomyine genera . 47 7. Consistency and retention indexes for sig- modontine characters 55 8. Consistency and retention indexes for phyllotine characters 68 VI Revision of the Tribe Phyllotini (Rodentia: Sigmodontinae), with a Phylogenetic Hypothesis for the Sigmodontinae Scott J. Steppan Abstract The phylogenetic relationships of the South American rodents of the tribe Phyllotini are reviewed, considering both the phylogenetic relationships of the phyllotines to the other sig- modontine tribes and the relationships within the phyllotines. Cladistic analysis of 40 mor- phological characters for 28 sigmodontine taxa provides a working hypothesis of sigmodontine phylogenetics, phyllotine monophyly, and likely sister-groups to the phyllotines. Five Old World and six New World cricetid taxa represent outgroups, and together they root the sigmodontine tree within a paraphyletic thomasomyine group. The analysis corroborates the recent proposal of a monophyletic oryzomyine group that includes the tetralophodont genera Holochilus, Pseu- doryzomys, and Zygodontomys. A supratribal clade is indicated that includes the Akodontini, Phyllotini, Scapteromyini, and Punomys. The distinctiveness and monophyly of the Central American tylomyine group is strongly supported. The taxonomic distribution of and variation in morphological characters of the dentition, skull, skeleton, and soft anatomy are discussed. Apparent biases in the evolutionary polarity of reductive characters are identified in detail from a broad taxonomic survey (174 species) for intra- and interspecific variation in number of vertebrae, as well as from optimization of other characters on the phylogenetic hypotheses. Conflicting results from various phylogenetic studies suggest that Sigmodon be considered Sigmodontinae incertae sedis. Pseudoryzomys and Punomys are removed from the phyllotines, and Phyllotini is diagnosed. A cladistic analysis of 35 phyllotine taxa using 98 morphological characters is presented, and the taxonomy of the phyllotine genera is revised. Species of An- dalgalomys are referred to Graomys. Removal of micropus from Auliscomys to the genus Loxodontomys is supported. The two most species-rich genera, Phyllotis and Calomys, appear to be paraphyletic, but their species relationships are insufficiently resolved to justify modifying their taxonomy at this time. Introduction The phyllotines constitute one of the principal radiations of the New World muroids. Frequently the most abundant mammals in their range, phyl- lotine species are concentrated among the pastoral habitats of the Andes, stretching from Ecuador to Tierra del Fuego, and from the Pacific coast of Peru and Chile east through Patagonia to south- eastern Brazil. Maximum diversity is achieved in the altiplano, with 44% of the phyllotine species inhabiting the puna, an alpine steppe community (Reig, 1986). This study presents a cladistic analysis of evo- lutionary relationships among members of the tribe Phyllotini. It then provides a taxonomic revision of the tribe with diagnoses of recognized genera within this phylogenetic context. An impediment to any such cladistic analysis within tribes is that intertribal relationships among Neotropical sig- modontine rodents, and even tribal monophyly, are poorly resolved. This lack of understanding of FIELDIANA: ZOOLOGY, N.S., NO. 80, FEBRUARY 28, 1995, PP. 1-112 Table 1 . Species included in sigmodontine analysis. (Taxonomy follows Musser and Carleton [1993], with modifications noted.) Old World "cricetids"" Subfamily Calomyscinae Calomyscus baluchi Subfamily Cricetinae Cricetulus migratohus Mesocricetus auratus Phodopus sungorus Subfamily Mystromyinae Mystromys albicaudatus New World "cricetids" Subfamily Tylomyinae'' Nyctomys sumichrasti Tylomys nudicaudus Subfamily Neotominae' Neotoma jloridana Ochrotomys nuttalli Peromyscus leucopus Scotinomys teguina Subfamily Sigmodontinae Tribe Akodontini"' Akodon albiventer Akodon boliviensis Oxymycterus hispidus Tribe Ichthyomyini Anotomys leander Ichthyomys hydrobates Neusticomys monticolus Tribe Oryzomyini'' Holochilus brasiliensis Neacomys spinosus Nectomys squamipes Oligoryzomys fulvescens Oryzomys capito Oryzomys palustris Pseudoryzomys simplex Zygodontomys brevicauda Tribe Phyllotini Calomys callosus Graomys griseoflavus Neotomys ebriosus Phyllotis darwini Reithrodon auritus Tribe Scapteromyini Kunsia tomentosus Scapteromys tumidus Tribe Sigmodontini Sigmodon hispidus Tribe Wiedomyini Wiedomys pyrrhorhinos Thomasomyine grour/ Chilomys instans Rhipidomys latimanus Thomasomys aureus Thomasomys baeops Thomasomys rhoadsi Sigmodontinae incertae sedis Punomys lemminus higher-level relationships significantly reduces confidence in hypotheses of character polarities and specific membership within tribes. Better es- timates of outgroups to the phyllotines are needed. Therefore, this study also presents a cladistic anal- ysis for the subfamily Sigmodontinae (sensu Reig, 1 980) in order to provide a provisional hypothesis of outgroup relationships to be applied to the phyl- lotine analysis, and a revised diagnosis of Phyl- lotini. These two nested analyses will be referred to as the sigmodontine and phyllotine analyses. Phyllotine membership and defining characters have fluctuated among studies, but nearly all workers have recognized the following taxa as phyllotines: Andalgalomys, Andinomys, Aulisco- mys, Calomys, Chinchillula, Eligmodontia, Gale- nomys, Graomys, Irenomys, and Phyllotis. Prob- lematic taxa have included Euneomys, Holochilus, Neotomys, Pseudoryzomys, Punomys, Reithrodon, Sigmodon, and Zygodontomys. "Problematic taxa" are those that at various times have been included within the phyllotine group as well as genera hy- pothesized to have been derived from a phyllotine ancestor. The phyllotine analysis examines rep- resentatives of all phyllotine genera, as defined by the results of the sigmodontine analysis. All for- mally or informally recognized supergeneric groups are represented in the sigmodontine analysis, as are all "problematic taxa" except Euneomys. Evolutionary Relationships within Sigmodontinae Native muroid rodents are represented in South America exclusively by the subfamily Sigmodon- tinae Wagner, 1 843. Debate continues as to wheth- er this taxon includes the North American "cri- ■ Informal designation of Old World and New World "cricetids" reflects historical usage and serves to distin- guish them from murines and arvicolines, but little sup- port has been presented for the monophyly of either group. h Sensu Reig (1984). The distinctiveness of this group and its basal position relative to the North American neotomine-peromyscines and South American sigmo- dontines has also been noted by Carleton (1980). < Sensu Reig (1980). d Sigmodontine tribes regarded as informal groups by Musser and Carleton ( 1 993) are here recognized in their formal tribal designations, sensu Vorontsov (1959). e Contents per Voss and Carleton (1993). ' Monophyly and tribal status argued against by Voss (1993). FIELDIANA: ZOOLOGY Tylomys Ototylomys Zygodontomys Calomys Phyllotis Oryzomys Nectomys Sigmodon Peromyscus Neotoma Mesocricetus 40 30 10 20 TIME (MYA) Fig. 1. Albumin immunological dendrogram of New World muroids (modified from Sarich, 1985). cetids," the neotomine-peromyscines (Carleton & Musser, 1984; Musser & Carleton, 1993), or is limited to the predominantly South American spe- cies sensu Reig (1980, 1986). The northern and southern continental groups have also been char- acterized as having "simple" or "complex" penis types, respectively (Hershkovitz, 1966b; Hooper & Musser, 1964). The subfamily Sigmodontinae is here considered to be limited to the predomi- nantly complex-penised, largely Neotropical spe- cies in accordance with the taxonomy of Reig (1980) and evolutionary scenarios of Hershkovitz ( 1 962, 1 966a), excluding the Central American ge- nus Nyctomys. The taxonomy of muroid rodents used in this paper is presented in Table 1 . Crice- tidae was not recognized by Musser and Carleton (1993), and in this paper I use the term "cricetid" for the assemblage of subfamilies sharing the den- tal morphology associated with earlier definitions of Cricetidae (Simpson, 1 945). Sigmodontinae (as was defined to include the North American neotomine-peromyscines) was one of only two muroid subfamilies that Carleton and Musser (1984, p. 300) were unable to diag- nose, owing to their "immense heterogeneity." Monophyly of the Neotropical "complex penis" sigmodontines has not been clearly demonstrated, but the few available molecular or cladistic studies are consistent with monophyly (Carleton, 1973; Catzeflis et al., 1993). While Carleton cautioned that assuming mono- phyly of the complex-penised sigmodontines ("South American cricetines") "as presently con- stituted" was premature (1980, p. 140), his dis- tance Wagner tree (1980, Fig. 41) does support monophyly of the Neotropical sigmodontines pro- vided they are not defined as identical with "com- plex penis" murids and the Central American Nyc- tomys is excluded. The distinctiveness of Nyctomys from the other "complex penis" forms has been noted repeatedly for several aspects of the male reproductive system (Arata, 1964; Hershkovitz, 1966b; Hooper & Musser, 1964; Voss & Linzey, 1981). Sarich (1985) presented an albumin im- munological dendrogram for New World "crice- tids" (Fig. 1 ). The South American sigmodontines as defined in this study were a monophyletic branch in an unresolved trichotomy with the Central American Tylomys (which Carleton [1980] found to be most closely related to Nyctomys) and the North American Peromyscus and Neotoma. Cat- zeflis et al. (1993) reported a DNA hybridization study that clearly distinguishes the North and South American groups as separate lineages and referred STEPPAN: REVISION OF THE TRIBE PHYLLOTINI them to the subfamilies Neotominae and Sigmo- dontinae, following Reig (1980). Neotominae was represented by Neotoma and Peromyscus while Sigmodontinae was represented by Sigmodon, Oryzomys, Zygodontomys, Akodon, and Phyllotis. Catzeflis et al.'s (1993) analysis and review of pre- vious DNA hybridization studies not only support the monophyly of the South American Sigmodon- tinae relative to the Neotominae, but also relative to other "cricetid" groups: cricetines and arvicol- ids. Molecular data sets thus support the definition of Sigmodontinae used in this paper. Additional support for a monophyletic Sigmo- dontinae comes from distributions of ectoparasites and endoparasites. Wenzel and Tipton (1966) found that mites and lice (as well as the less host- specific ticks) found on complex-penised "crice- tids" (sigmodontines) belonged to a radiation of South American origin. Congruently, Slaughter and Ubelaker (1984) found members of the nematode genus Parastrongylus, belonging to a species group largely restricted to Old World "cricetids," to be present in several oryzomyines and Sigmodon, but not in North American neotomine-peromyscines. The nematodes show strong host specificity and are not likely to have distributions strongly af- fected by climate, a criticism Carleton (1 980) made of the flea data from Wenzel and Tipton (1966). Slaughter and Ubelaker (1984) argued that the neotomine-peromyscines had diverged from the lineage that later gave rise to the Old World "cri- cetids" and the sigmodontines prior to the com- plex-penised lineage having acquired the parasite. Few hypotheses of relationships among the sig- modontines have been proposed, and only one has utilized phylogenetic methods (Carleton, 1980), wherein the analysis of the South American sig- modontines was peripheral to the principal objec- tives of the study. More comprehensive attempts (Gardner &Patton, 1976; Hershkovitz, 1962; Reig, 1 986) have lacked the analytical rigor of cladistics. Nonetheless, the several scenarios and studies pro- vide an important conceptual framework. The group most commonly identified as the bas- al member of the sigmodontines has been the spe- cies-rich oryzomyines, which have often been por- trayed as paraphyletic. The definition of "oryzomyines" has varied, either referring to ory- zomyines sensu stricto (Melanomys, Microryzo- mys, Neacomys, Nectomys, Nesoryzomys, Oeco- mys, Oligoryzomys, Oryzomys, Scolomys, Sigmodontomys [Hershkovitz, 1962; Musser & Carleton, 1993]) or also including the thomaso- myines (Thomasomys, Rhipidomys, Delomys, Chilomys, Aepeomys [Reig, 1980]). Gardner and Patton (1976) derived all sigmodontine lineages from an Oryzomys karyotype. Reig (1986, 1987) considered oryzomyines to be the direct or indirect descendants [sic] of the ancestral Oryzomys-like sigmodontine. Carleton's (1980, Fig. 41) Wagner tree placed Akodon and Oxymycterus at the base of the South American lineage, while Sarich's (1985) immunological tree (Fig. 1) placed Sig- modon at the base of the South American branch, with Zygodontomys basal to the phyllotines and oryzomyines sensu stricto. Hershkovitz (1962) envisioned two lineages arising from a pentalophodont (with complete me- solophostyle), Thomasomys-like stock: a thoma- somyine group that gave rise to the oryzomyine group, and a tetralophodont lineage that gave rise to the paraphyletic akodontine group, from which radiated the ichthyomyine, phyllotine, and sig- modont groups (Fig. 2). Later, he presented the scapteromyines as the sister-group to the oxy- mycterines, and these together as part of the ako- dont radiation (Hershkovitz, 1966b). Vorontsov (1959) outlined what amounts to a monophyletic group consisting of his Phyllotini, Euneomys, and Sigmodontini (including Reithrodon and Neoto- mys). The Wagner tree generated by Carleton ( 1 980) placed Oxymycterus as a basal South Amer- ican genus and Scapteromys as highly derived, in contrast to his earlier noncladistic study of stom- ach morphology that hypothesized a sister-group relationship between these two (Carleton, 1973). The evolutionary scenario diagrammed by Gard- ner and Patton (1976) treats the akodontines and oxymycterines as sister-groups comprising an in- dependent offshoot from Oryzomys. Other inde- pendent lineages include the thomasomyines, ichthyomyines, and a group composed of the phyl- lotines, sigmodonts, and scapteromyines. Finally, Reig (1984, 1986) wove a complex bio- geographic scenario for the South American "cri- cetids." He considered phyllotines to be most like- ly derived from akodontines, though he suggested that phyllotines could be independent offshoots from the oryzomyines. He also hypothesized that Zygodontomys was an independent oryzomyine offshoot of undetermined affinity and proposed the descent of ichthyomyines from a Thomaso- mys-like ancestor, scapteromyines from akodon- tines, and sigmodonts from the phyllotine Neo- tomys. Although there is no single point on which all of these authors agree, a consensus would place the oryzomyines or thomasomyines at the root of the sigmodontines. FIELDIANA: ZOOLOGY SYLVAN iv .^p-~-- — PASTORAL X ;^ . , i * 2 ^' l-V-+s,v, ANDI CHINCHILLULA NOMYS PENTALOPHODONT SYLVAN CRICETINES Fig. 2. Evolutionary scenario for the South American sigmodontines (from Hershkovitz, 1962). STEPPAN: REVISION OF THE TRIBE PHYLLOTINI Oryzomys Holochilus Sigmomys Oxymycterus Akodon Eligmodontla Neacomys, Notiomys Sigmodon Rheomys Nyctomys Fig. 3. Hypothesized relationships of South American "cricetines," based on phallic characters (from Hooper & Musser, 1964). Taxonomic History of the Phyllotines The following is a summary of the more recent taxonomic history of the phyllotines. Additional details, particularly of the period before 1962, can be found in Olds and Anderson (1 989) and in Tate (1932a,b,c). Hershkovitz (1962, and Fig. 2) portrayed the phyllotines as a monophyletic group derived from akodont stock. In his detailed revision of the phyl- lotines and discussion of sigmodontine morpho- logical evolution, Hershkovitz included Zygodon- tomys (whose southern forms have since been removed to Bolomys) and Pseudoryzomys but ex- cluded Reithrodon and Neotomys (which he con- sidered to be sigmodonts along with Sigmodon and Holochilus), as well as Euneomys, Irenomys, and Punomys. The glans penis of Neotropical "cricetids" was first systematically examined by Hooper and Mus- ser (1964), who inferred evolutionary relation- ships among 1 9 genera based on estimates of over- all similarity (Fig. 3). They found no diagnostic trait among the diverse phalli of five phyllotine genera. They seem to have excluded Zygodonto- mys (diagrammed near the base of the sigmodon- tine radiation; Fig. 3), although their discussion indicates that it could also be placed at the base of the phyllotines. The cited similarity between Eligmodontia and Akodon could lead to the in- terpretation of Eligmodontia as either a basal phyl- lotine or akodontine. They suggested that Holo- chilus was best placed with the oryzomyines. Reithrodon was placed as a basal phyllotine; Neo- tomys and Pseudoryzomys were not examined. In- explicably, Geoxus {"Notiomys") was dia- grammed as part of a phyllotine lineage, though in the text it was described as allied to akodontines, Oxymycterus, and phyllotines. Phyllotines have commonly been viewed as a paraphyletic group. Gardner and Patton (1976) diagrammed their view of evolutionary relation- ships among Neotropical "cricetids" based pri- marily on karyotypic data. They showed sigmo- donts and scapteromyines as derived from primitive phyllotines. Pearson and Patton (1976) and Gardner and Patton (1976) agreed on the in- clusion of Andinomys, Auliscomys, Calomys, Chinchillula, Eligmodontia, Neotomys, Phyllotis (including Graomys), and Reithrodon as phyllo- tines. Their analysis relied on similarity in number and form of unhanded chromosomes. They ex- plicitly excluded Zygodontomys but did not ex- amine the genera A ndalgalomys (first described in 1978 as a Graomys), Euneomys, Galenomys, Ir- enomys, Pseudoryzomys, or Punomys. Reig (1980, 1986) viewed all the major sigmo- dontine tribes as paraphyletic and stated that the phyllotines most likely evolved "directly from the oryzomyines through the akodontines" (Reig, 1 986, p. 426). Reig ( 1 986) also suggested that both sigmodont genera, Holochilus and Sigmodon, were (independently?) derived from a Neotomys-like ancestor in Peru. Spotorno (1986) explored the akodontine and FIELDIANA: ZOOLOGY phyllotine radiations (which he viewed as sister- groups) using banded karyotypes, electrophoresis, glans penis and bacular morphology, and cranial morphometries. He argued that the phyllotines were monophyletic, citing simplification and pla- nation of their molars, differentiation of the distal baculum, and a poorly developed base of the prox- imal baculum as characteristic features. Like Hershkovitz (1962) and Reig (1986), Spotorno considered the phyllotines to be derived from an akodontine ancestor. Though he drew no definite conclusions about phylogenetic relationships be- tween genera, his concept of the phyllotines in- cluded Andinomys, Auliscomys, Calomys, Chin- chillula, Eligmodontia, Euneomys, Graomys, Irenomys, Phyllotis, and Reithrodon. Spotorno did not explain why he considered Reithrodon a phyl- lotine but Neotomys a sigmodont. Punomys was listed as Sigmodontinae incertae sedis and not an- alyzed. Pseudoryzomys and Zygodontomys were omitted. Olds and Anderson (1989) presented the first formal diagnosis of Phyllotini and the first im- plicitly cladistic treatment of the group, providing a foundation for this examination of phyllotine monophyly and tribal relationships. They includ- ed Punomys and excluded Pseudoryzomys and Zygodontomys. In their survey of 33 sigmodontine genera ( 1 4 phyllotine and 1 9 nonphyllotine), they could not find any unique synapomorphies for the phyllotines. All phyllotines were found to have the following combination of characters: hairy heel, ears moderate to large, palate long (except in Irenomys), incisive foramina long, parapterygoid fossa relatively broader than mesopterygoid fossa (ex- cept in Punomys), sphenopalatine vacuities large, su- praorbital region never evenly curved in cross section, interparietal well developed, zygomatic notch deeply excised (less so in Irenomys), teeth tetralophodont, M3 more than half the length of M2. (Olds & An- derson, 1989, p. 63.) Determining whether these characters are actually synapomorphies for the phyllotines requires a phylogenetic hypothesis for the subfamily. Olds and Anderson (1989) incorporated into their di- agnosis characters that "may be synapomorphic" and recognized the difficulty of diagnosing the phyllotines given the current knowledge of tribal relationships by describing the diagnosis as a "hy- pothesis for future testing and elaboration" (p. 63). I will test their hypotheses of phyllotine mono- phyly and associated synapomorphies by con- ducting a more broadly based cladistic analysis for the subfamily. Olds and Anderson (1989) also identified and diagnosed a distinct "Reithrodon-group" that in- cluded Euneomys and Neotomys. They alluded to a relationship of this group to the remaining sig- modonts but left this relationship unspecified. Braun (1993) generally agreed with Olds and Anderson (1989) on the composition of Phyllotini but additionally included Pseudoryzomys as the most basal phyllotine. She did not recognize a Reithrodon group but instead found support for a generic group that included Reithrodon, Euneo- mys, Neotomys, and Auliscomys along with An- dinomys, Chinchillula, Galenomys, Irenomys, and Punomys. Braun also elevated Auliscomys boli- viensis to Maresomys, reinstated Paralomys for Phyllotis gerbillus, additionally including Phyllotis amicus in the reinstated genus, and resurrected Loxodontomys for micropus, which she removed from Auliscomys. In an earlier version of this study (Steppan, 1 993), using nearly the same phyllotine data set (see Ma- terials and Methods), I excluded Punomys from the phyllotines. Phyllotis was found to be para- phyletic, but the internal nodes were very poorly resolved. Calomys was also paraphyletic, with C. sorellus as the sister-species to all remaining phyl- lotines. Confirmation was found for the Reithro- don group, which was most closely related to Au- liscomys, Galenomys, and the resurrected Loxodontomys. Graomys appeared paraphyletic with respect to Andalgalomys, but character sup- port was not strong. Eligmodontia was most close- ly related to Graomys, and this group appeared to be derived from Phyllotis. Materials and Methods Taxa and Characters Examined Two separate but nested phylogenetic analyses were conducted: one on the Sigmodontinae and one on the Phyllotini. The sigmodontine analysis included 29 ingroup species representing all named tribes or major generic-groups. Eleven outgroup taxa included Nyctomys and Tylomys (Central American genera of uncertain affinities to the sig- modontines and neotomine-peromyscines), the terminal neotomine-peromyscines Neotoma and Peromyscus, the basal neotomine-peromyscines Ochrotomys and Scotinomys (Carleton, 1 980), and the Old World "cricetids" Calomyscus, Cricetulus, Mesocricetus, Phodopus, and Mystromys. Rela- STEPPAN: REVISION OF THE TRIBE PHYLLOTINI Table 2. Species included in phyllotine analysis. Thomasomyine group Thomasomys baeops Tribe Oryzomyini Holochilus brasiliensis Nectomys squamipes Pseudoryzomys simplex Zygodontomys brevicauda Tribe Ichthyomyini Ichthyomys hydrobates Tribe Akodontini Akodon albi venter Akodon boliviensis Chroeomys andinus Oxymycterus hispidus Tribe Scapteromyini Scapteromys tumidus Sigmodontinae incertae sedis Punomys lemminus Tribe Phyllotini Andalgalomys pearsoni Andinomys edax A uliscomys boliviensis Auliscomys pictus Auliscomys sublimis Calomys callosus Calomys hummelincki Calomys laucha Calomys lepidus Calomys sorellus Chinchillula sahamae Eligmodontia morgani Euneomys chinchilloides Euneomys petersoni Galenomys garleppi Graomys domorum Graomys griseoflavus Irenomys tarsalis Loxodontomys micropus Neotomys ebriosus Phyllotis amicus Phyllotis andium Phyllotis caprinus Phyllotis darwini Phyllotis definitus Phyllotis gerbillus Phyllotis haggardi Phyllotis magister Phyllotis osilae Phyllotis wolffsohni Phyllotis xanthopygus rupestris Phyllotis xanthopygus xanthopygus Reithrodon auritus evae Reithrodon auritus pachycephalus Reithrodon typicus " Removal of micropus from Auliscomys to Loxodon- tomys recommended by Braun (1993) and Steppan ( 1 993). tionships among the Old World "cricetids" are unclear, but in a recent treatment (Musser & Carle- ton, 1993) these five taxa represented the murid subfamilies Calomyscinae, Cricetinae, and Mys- tromyinae (see Table 1 , with subfamily and tribal classification). Estimates of the number of phyl- lotine species vary with group limits and specific status of taxa, with most estimates between 40 and 45. The phyllotine analysis included 35 phyllotine OTUs representing 33 putative species in 14 phyl- lotine genera, in addition to 1 2 species belonging to 1 1 outgroup genera (Table 2). Character assessments were made from direct examination of museum specimens (Field Muse- um of Natural History, Chicago, fmnh; Museum of Vertebrate Zoology, University of California, Berkeley, mvz; National Museum of Natural His- tory, Smithsonian Institution, Washington, D.C., usnm; University of Michigan Museum of Zool- ogy, Ann Arbor, ummz; Museo Nacional de His- toria Natural, Santiago, Chile, mnhn; The Muse- um, Michigan State University, East Lansing, msu; specimens examined listed in the Appendix). Phal- lic measurements for some species were measured from published illustrations (Hooper & Musser, 1964; Spotorno, 1986). Evidence of two pairs of preputial glands was gathered from the literature (Voss & Linzey, 1981) for some species. Stomach and some hyoid data are from Carleton (1980), gallbladder data are from Voss (1991), and mam- mae number is from Gyldenstolpe (1932), Hersh- kovitz(1955, 1959, 1962, 1966b), and Olds (1988). Dental nomenclature follows Reig (1977, and Fig. 4). A broad survey of characters from varied ana- tomical systems was conducted, resulting in 40 characters for the sigmodontine analysis and 98 characters in the phyllotine analysis covering den- tal, cranial, postcranial, external, gastrointestinal, and male reproductive tract systems. Seventeen characters were shared by the two analyses, but 5 of the 1 7 were coded differently in each. Many of those 1 7 were included in the phyllotine analysis to help define outgroup relationships. Previous surveys have found little variation in soft anatomy among phyllotines that was not already evidenced in the skeleton (Carleton, 1973; Voss & Linzey, 1981; Voss, 1991). The 40 sigmodontine charac- ters represent 1 1 4 character states and a minimum of 74 character state transitions. The 98 phyllotine characters represent 265 character states and a minimum of 167 character state transitions. Char- acter state descriptions were defined so as to be more objective or quantitative than they have been in the past. Ambiguous terms such as "relatively broad," "large," or "well developed" were gen- erally but not entirely avoided. Quantitative char- acters or those with quantitative components were FIELDIANA: ZOOLOGY Anterohngual conule Protostyle Anterolabial conulid Protoflexid Protostyhd Anterolabia cingulum Anterior murid PROTOCONID Hypoflexid Ectoslylid Ectolophid Mesoconid Median muri d HYPOCONID Anterolabial conule Anterof lexus Anteroloph Parastyle Paraflexus Protophule Paroloph PARACONE Paralophule Mesoflexus Mesostyle Mesoloph Metaflexus Metalophule METACONE Metoloph Posteroflex js Posterostyle Posteroloph Anterolingual conulid Anteroflexid Anterolophid Metastylid Metaflexid Metalophid METACONID Protolophulid Metalophulid Mesof lexid Mesolophid Mesostylid Entoflexid Entolophulid ENTOCONID Entolophid Posteroflexid Hypolophulid Posterostylid Posterolophid Fig. 4. Master plan of the occlusal surfaces of idealized first upper and lower molars of a cricetid rodent. All possible elements are shown with their corresponding names (from Reig, 1 980). measured using a digital caliper precise to ± 0.005 mm and values were rounded to the nearest 0. 1 mm for coding. External measurements were re- corded from specimen tags. Character polarities were determined by outgroup rooting within the parsimony analysis rather than a priori, so ple- siomorphic character states are not always desig- nated "0." Characters were treated as ordered un- less otherwise noted. Outgroup taxa in the phyllotine analysis were selected to include representatives of each of the sigmodontine tribes and major generic groups (ex- STEPPAN: REVISION OF THE TRIBE PHYLLOTINI MDH-' EAP* ACON •* t c j-C _JPEP PEP CI* PEP B2 C MDH 1* PEP Dl" ■ And 'Abe SI, ■ P.r •Mm ■ Mui £ -cE Reithrodon Auliscomys Phyllotis Eligmodontia Reithrodontomys Peromyscus Irenomys Andinomys Euneomys Abrothrix Oligoryzomys Oryzomys b Sigmodon Scotinomys Neotoma Microtis Mesocricetus Mus Rattus Fig. 5. A. UPGMA dendrogram of electrophoretic similarities (from Spotorno, 1 986). B. Seventy percent majority- rule consensus tree of 1 4 1 equally most-parsimonious trees derived from the original allele data. In cladistic reanalysis, individual alleles were treated as character states, proteins as characters. Character states were unordered in a cladistic analysis using PAUP. A strict consensus of the most-parsimonious trees is completely unresolved. cept the monotypic Wiedomyini). Both analyses used the preferred method of Maddison et al. ( 1 984) when outgroup relationships are not well resolved, by simultaneously resolving ingroup and outgroup relationships under global parsimony. The result- ing sigmodontine network was rooted by desig- nating the Old World "cricetids" as outgroups. The phyllotine network was rooted in accordance with the results from the sigmodontine phylogeny and consistent with the common estimate of basal sigmodontines (Hershkovitz, 1962; Reig, 1980, 1986; Voss, 1993; Voss & Carleton, 1993). Sig- modon was not included in the final phyllotine analysis because previous molecular and morpho- logical phylogenies were highly discordant on its position among sigmodontines. DNA hybridiza- tion has been reported to show Sigmodon to be the basal member of a Neotropical group, outside a group that included the oryzomyines, Akodon, and Phyllotis (Catzeflis et al., 1993), though the data were not presented. Likewise, albumin im- munological distances placed Sigmodon outside a clade that included oryzomyines, akodontines, phyllotines, and ichthyomyines (Sarich, 1985). Sigmodon was clustered with the North American neotomine-peromyscines in phenetic (Spotorno, 1986, and Fig. 5 A) and cladistic (Fig. 5B; reanaly- sis of data in Spotorno, 1986) analyses of electro- phoretic data, and its inclusion resulted in three discordant and unconventional tree topologies with this data set (see Discussion under Phylogenetic Relationships within Sigmodontinae). Quantitative Character Coding Quantitative characters, in this case the four ra- tio characters (M3 length/M2 length, M2 width/ M2 length, ear/body, interparietal/parietal), were coded using a minor variation on segment-coding (Chappill, 1989). In segment-coding, itself a vari- ation of range-coding (Colless, 1 980), the total range of mean values for the taxa is divided into a num- ber of equal-length segments. Segment-coding cat- egorizes an ordered series of OTUs into discrete character states by creating a discriminant crite- rion that is a multiple of the pooled within-group standard deviation. Thus, the extent to which OTUs are grouped together is objectively deter- mined by the actual observed variability within each of the OTUs. This characteristic of segment- coding and similar techniques, such as generalized gap-coding (Archie, 1985), is justified by the ar- gument that the ease with which an evolutionary unit can evolve from one character state to another (e.g., response to selection) is a function of the amount of genetic variance present for that trait (Farris, 1966; Kluge & Farris, 1969; Archie, 1985). Segment-coding proceeds by first calculating the pooled within-group standard deviation (s p ) for the set of taxa and then choosing a value for the 10 FIELDIANA: ZOOLOGY multiplier (c). This size of the multiplier deter- mines the percentage of overlap between the dis- tributions of two OTUs (e.g., ls p = 31% overlap between two populations, 3s p = 7% overlap) (Ar- chie, 1985). Use of larger multipliers represents a more conservative estimate of the number of bi- ologically significant state transitions. Characters that vary little between taxa but show high intra- specific variability would be subdivided less than characters with relatively little intraspecific vari- ation. The OTUs are then ordered (usually as- cending) by the magnitude of their means. Starting at one end of the series, all those OTUs that fall within a group bounded by cs p are joined in a "segment." This step is repeated for each subse- quent segment. The process is repeated until the last OTU in the series has been joined into a seg- ment. These subsets are then converted to codes by increasing the code value by 1 for each segment transition. The size of the segments is determined a priori as a multiple, c, of the pooled within-group standard deviation, s p . In this way, the number of character states is determined by the amount of infraspecific variation relative to interspecific variation. One drawback of generalized gap-coding and its related techniques is that the position of one end of a subset is strongly influenced by the distribu- tion of OTU values at the other end. Nearly iden- tical OTUs can be categorized into two different states because of the specific value of the OTU at the other end of the subset. In other words, taxon sampling can significantly affect a generalized gap- coding scheme and the addition of even a single taxon can require a recoding of all others. Tradi- tional gap-coding techniques place state transi- tions at large gaps but have a series of other short- comings. The number of character states increases with the number of OTUs in generalized gap-cod- ing, independent of the range and multiplier value (the number often decreases in gap-coding). With a large number of OTUs, there will be a large number of character states. If the magnitude of the multiplier is increased to compensate for this ef- fect, the result is to concentrate the transitions toward the extremes of the series, decreasing the phylogenetic information content. Standardizing segment (group) lengths a priori minimizes or eliminates these shortcomings. For more detailed discussions and critiques of the various quanti- tative coding techniques, the reader is referred to prior studies (Archie, 1985;Chappill, 1989; Mick- evich & Farris, 1981) and references therein. The modification used in this study is to allow the segments, whose lengths were calculated a priori, to shift as a group so that segment bound- aries could fall within the largest available gaps. The segments were not allowed to shift more than one-half a segment. The objective of this shift was to avoid arbitrarily splitting two taxa with very similar values and placing them into different character states. The multiplier used for all four quantitative characters was 4, chosen to yield an overlap between OTUs of less than 5% (Archie, 1985). This is larger than that recommended by Chappill (1989), who preferred 'A or l h (yielding overlaps of 45% and 40%, respectively), but those small multiplier values would result in dozens of character states for each character, raising the like- lihood of excessive influence by the quantitative characters on the phylogenetic analysis. A multi- plier of 4 is commonly used with generalized gap- coding and its related techniques. Analytical Methods Phylogenetic hypotheses were generated under the principle of Wagner parsimony using the com- puter program PAUP, version 3.1.1 (Swofford, 1993). Heuristic tree-search algorithms were em- ployed rather than the exact methods of exhaus- tive search or branch-and-bound, which required prohibitively long computer runs with the many taxa included in this study. Minimum-length trees were accumulated from multiple replicate analy- ses, each starting with a different random tree. Experience with these data sets demonstrated that with this many taxa (>40), most single replicates will not find trees of the minimum length. Con- sensus trees were produced from the accumulated minimum-length trees. The sensitivity of the re- sulting topologies was tested by multiple runs in which particularly interesting or pivotal taxa or characters were excluded. Additionally, 100 (sig- modontine) and 200 (phyllotine) replicate boot- strap analyses were performed on the data sets to provide nonparametric estimates for the confi- dence to be placed in each node of the trees. Boot- strapping randomly resamples the characters in the data set with replacement (Felsenstein, 1985). The tree-search algorithm of PAUP can be con- strained so that it retains only those trees con- forming to an a priori tree topology. The difference in tree length between the most-parsimonious trees overall and the constrained tree provides addi- tional information in evaluating alternative phy- STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 11 Table 3. Data matrix for sigmodontine analysis. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Oryzomys capito 2 2 1 1 2/3 0/1 2 Oryzomys palustris 2 1 2 0/1 1 3 1 Oligoryzomys fulvescens 2 1/2 1 2 Nectomys squamipes 2 2 2 3 1 Neacomys spinosus 2 1 1 1 3 0/1 Zygodontomys brevicauda 1 1 1 2 1/2 3 Pseudoryzomys simplex 1 0/1 2 1 3 Holochilus brasiliensis 2 1 2 1 3 Akodon boliviensis 1 2 1 2 1 2 1 Akodon albiventer 1 2 1 2 1 2 1/2 Oxymycterus hispidus 1 1 1/2 2 1 2 2 Anotomys leander 1 1 1 1/2 1 Ichthyomys hydrobates ? 1 2 2 Neusticomys monticolus 0/1 1 2 ? Chilomys instans 2 1 1 1 0/1 1 Rhipidomys latimanus 2 0/1 1 1 1 3 0/1 1 Thomasomys aureus 2 1 1 0/1 1 1 2 1 1 Thomasomys baeops 2 0/1 1 1 0/1 2 1 1 Thomasomys rhoadsi 2 0/1 2 1 1 Wiedomys pyrrhorhinos 2 0/1 1/2 1 2/3 1 Kunsia tomentosus ? 1 1 2 1 2 3 2 1 Scapteromys tumidus 1 1 1 2 2 1 Calomys callosus 1 2 1 3 1 Graomys griseoflavus 1 1 1 2 1 1 3 1 Phyllotis darwini 1 1 1 1 2 1 2 1 Neotomys ebriosus 2 1 2 1 2 1 2 9 1 0/1 Reithrodon physodes 3 2 1 2 1 1/2 2 1 2 1 Punomys lemminus 1 1 1 2 2 2 2 1 1 Sigmodon hispidus 1 1 0/1 2 1 3 1 1 Nyctomys sumichrasti 2 0/1 1 1 3 2 1 1 Tylomys nudicaudus 1 1 1 1 1 3 2 1 1 Ochrotomys nuttalli 2 1 0/1 1 1 1 0/1 1 Scotinomys teguina ? 0/1 1 1 1 0/1 1 2 1 Neotomys floridana 1 1 1/2 1 2/3 2 1 Peromyscus leucopus 2 1 1 1 1 Calomyscus baluchi 1 1 2 2 Cricetulus migratorius 0/1 1 2 1 Mesocricetus auratus 2 ? 0/1 2 ? 1 Mystromys albicaudatus 2 1 0/1 2 1/2 2 1 Phodopus sungorus 0/1 1 1 1/2 1 logenetic hypotheses. Twenty such phyllotine and nine sigmodontine hypotheses were evaluated, with as many as 54 replicate analyses run under a single constraint. Character transformations were opti- mized assuming both delayed transformation, which favors parallelisms over reversals, and ac- celerated transformation, which favors reversals over parallelisms. Only unequivocal character state changes are reported as hypothetical synapomor- phies. Consistency and retention indexes among ingroup taxa were calculated for each character. The consistency index (CI) is the minimum pos- sible number of character state transformations divided by the number of times that character is hypothesized to change across a tree. The retention index (RI) is related to the CI and can be thought of as an estimate of the informativeness of a char- acter in regard to groupings (Farris, 1989, p. 418). The sigmodontine analysis was also conducted with the inclusion of a weighted dummy variable so as to bias the analysis toward the a priori as- sumption of sigmodontine monophyly. This al- lows a larger set of trees to be considered than while employing topological constraints, increas- ing the likelihood of finding the most-parsimo- nious trees. The sigmodontine analysis was not meant as a test of monophyly, and both con- strained and unconstrained analyses were com- pared. Previous studies generally supported sig- modontine monophyly (Carleton, 1980; Catzeflis 12 FIELDIANA: ZOOLOGY Table 3. Extended. 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 0/1 1 1 ? 1 2 3 1 1 1 3 2 1 1 1 1 1 2 1 2 2 2 1 1 2 2 1 ? 1/2 1 1 1 1 2 1 2 2 1/2 9 9 1 3 2 2 2 1 2 1 2 2 2 ? ? 2 2 1 1 1 2 ? 1 1 2 1 9 ? 9 3 2 1 1 1 1 1 1 ? 1 2 2/3 2 9 9 1 1 1 2 1 0/1 1 1 1 1 0/2 9 1 2 3 2 ? ? ? 2 2 9 1 1 1 3 2 2 1 2 2/3 1/2 ? 7 1 9 1 3 1 2 1 2 3 2 2 2 1 1 3 9 ? 2 2 1 1 1 1 2 3 2 2 2 1 1 3 1 1 1 2 2 9 1 1 ? 1 2 ? ? 1 1 3 1 1 1 3 2 2 1 3 2 0/1 1/2 1 2 2 1 2 9 9 9 9 ? 1 1 1 1 1 2 1 3 1 2 2 1 1 2 9 ? 9 9 ? 1 1 1 2 1 3 2 2 2 1 1 2 9 ? 1 1 1 1 1 1 1 ? 1 1 0/1 9 9 ? 3 9 1 1 0/1 0/1 3 2 ? 1 1 1 1 9 ? 9 2 ? ? 1 3 2 ? 1 1 0/1 9 1 1 2 6 ? 1 1 1 0/1 1 3 2 ? 1 1 0/1 0/1 9 9 9 9 1 3 ? 1 1 3 2 2 ? 1 1 ? 9 9 9 9 1 2 9 1 1/2 1 1/2 3 2 ? 1 2 1 1/2 9 9 9 9 1 3 9 9 9 9 9 2 1 2 2 2 2 ? ? ? ? ? 9 ? 9 9 1 2 2 9 1 ? 9 0/1 2 2 2 ? 1 1 3 6 9 9 9 1 2 2 9 1 1 2 2 2 3 2 0/2 2 1 2 4 1 1 1 3 3 1 1 2 2 3 1 2 2 2 1 2 2 9 9 1 3 2 2 1 2 2 3 1 2 2 1 1 2 1 1 1 3 2 2 1 2 2 3 3 1 9 1 1 ? 9 ? 1 2 2 2 1 2 2 3 1 2 9 1 2 4 9 9 2 3 2 2 1 1 2 2 1 2 9 ? ? ? 9 ? 9 9 9 1 2 ? ? 9 9 9 1 2 3 2 2 2 1 2 4 1 1 1 1 2 3 2 1 2 1 3 0/1 2 1 1 1 1 1 9 9 2 ? 2 2 3 1 2 2 1 1 9 2 1 2 1/2 3 2 2 1 1 1 3 1 9 ? 3 1 1 1 1 1 3 2 1 1 1 3 9 1 1 3 1 1 1 1 3 1 2 1 1 2/3 1 9 2 1 2 2 1 2 3 2 2 1 1 1 3 1 1 1 9 3 1 1 2 1 2 1 3 2 2 ? 1 3 1 1 1 9 9 1 3 ? ? ? 1 1 1 2 3 2 2 1 1 4/5 1 1 9 2 2 2 2 1 9 2 2 2 2 1 5 1 1 ? ? 2 1 ? 2 9 2 1 1 2 9 9 1 4 9 9 9 9 9 ? ? 9 9 9 9 1 2 ? 1/2 2 ? 2 9 1 1 5 1 1 1 9 2 ? 9 9 9 ? et al., 1 993; Hooper & Musser, 1 964), but the issue has not been explicitly tested cladistically. The data set used in the phyllotine analysis is generally the same as that published previously (Steppan, 1993, Table 1), with several changes. Five characters were added (42P, 46P, 47P, 54P, 55P), several were redescribed and recoded to bet- ter describe the observed variation (e.g., 59P, 76P, 77P), four were deleted after additional data dem- onstrated higher infraspecific variability, and ty- pographical errors were corrected. Additionally, the undescribed species from Tapecua, Bolivia, collected by Sydney Anderson, that was referred to in Steppan (1993) is not included in this study, pending a formal description. Comparative Morphology For the characters discussed below, numbers preceded by "S" and "P" refer to their numbers in the sigmodontine and phyllotine analyses, re- spectively, as listed in the two data matrixes (Ta- bles 3, 4). Several characters without numbers are discussed because they are autapomorphies or are systematically valuable even if they were phylo- genetically uninformative within the context of this phylogenetic analysis. Character states were treated in the analysis as ordered, except where noted otherwise. Transfor- mation series were generally hypothesized to be linear, but orderings of the character states do not STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 13 Table 4. Data matrix for phyllotine analysis. 1 2 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Thomasomys baeops Ichthyomys hydrobates Holochilus brasiliensis Nectomys squamipes Pseudoryzomys simplex Zygodontomys brevicauda Akodon albi venter Akodon boliviensis Chroeomys andinus Oxymycterus hispidus Scapteromys tumidus Punomys lemminus Calomys callosus Calomys hummelincki Calomys laucha Calomys lepidus Calomys sorellus Andalgalomys pearsoni Graomys domorum Graomys griseoflavus Eligmodontia morgani Galenomys garleppi Auliscomys boliviensis Auliscomys pictus Auliscomys sublimis Euneomys chinchilloides Euneomys petersoni Reithrodon auritus evae Reithrodon auritus pachycephalus Reithrodon typicus Neotomys ebriosus Loxodontomys micropus Irenomys tarsalis Andinomys edax Chinchillula sahamae Phyllotis amicus Phyllotis andium Phyllotis caprinus Phyllotis darwini Phyllotis definitus Phyllotis gerbillus Phyllotis haggardi Phyllotis magister Phyllotis osilae Phyllotis wolffsohni Phyllotis xanthopygus rupestris Phyllotis xanthopygus xanthopygus 9 9 9 9 9 9 1 1 2 2 2 1 2 2 2 2 9 2 1 1 1 2 2 ? 1 2 2 ? 1 1 2 2 2 2 2 2 2 9 1 1 1 3 2 1 2 2 1 1 1 3 2 1 2 2 1 ? 1 2 1 2 1 1 1 1 ? 1 1 1 1 2 1 1 2 1 1 9 9 1 2 1 1 1 1 9 1 1 1 1 1 1 1 1 1 2 1 1 1 1 1 1 1 2 1 9 9 ? 9 9 ? 1 2 2 1 2 2 1 1 1 2 1 2 2 1 1 9 2 1 2 2 1 1 1 1 2 1 1 2 2 1 1 1 1 2 1 1 2 2 1 9 9 1 2 1 1 1 2 2 1 1 1 1 3 1 2 1 9 2 2 1 2 3 2 2 1 2 2 1 2 3 2 2 1 1 1 2 3 2 2 1 2 9 1 9 1 1 2 1 1 9 1 1 2 1 1 1 9 9 ? 1 1 9 2 2 ? 1 1 9 1 1 1 1 2 2 2 2 1 1 1 2 1 1 3 2 2 1 2 2 2 1 2 1 2 1 2 2 2 1 2 1 3 9 9 9 9 9 9 9 2 1 2 9 2 3 2 2 1 1 2 1 2 2 2 3 9 9 9 9 9 9 9 2 1 2 2 2 4 2 1 1 2 1 2 3 2 2 9 1 1 1 1 2 2 ? 2 3 1 1 2 2 1 1 1 1 2 2 1 2 1 2 2 1 1 2 1 ? 9 2 ? 1 2 1 ? 2 2 1 1 2 1 ? 1 2 9 ? 9 ? 1 2 2 ? 2 2 1 1 1 2 2 ? 1 1 2 9 1 9 9 2 1 ? 1 9 2 1 1 1 2 2 1 2 2 1 2 2 ? 1 2 1 1 2 2 ? 1 2 1 1 2 1 3 1 0/1 2 1 1 2 2 ? 1 2 1 1 1 2 2 ? 1 2 1 1 9 1 2 2 ? 1 imply polarity (i.e., "0" is not necessarily primi- tive). General cranial features referred to in the char- acter discussions are diagrammed in Figures 6-8. Dentition = absent 1 = fine striae 2 = 1 mediolateral shallow groove 3 = 1 mediolateral deep groove; 1 small shallow groove on midline 4 = 1 involuted groove on lateral corner IP. Incisor Grooves— Grooves on upper inci- sors— 5 states (Fig. 9). Although incisor grooves are unusual in other muroids, groove morphologies are relatively di- 14 FIELDIANA: ZOOLOGY Table 4. Extended. 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 3 1 1 2 1 1 2 1 1 1 1 1 1 1 0/1 1 1 1 1 1 1 ? 2 ? 1 3 1 ? 9 9 9 9 ? 1 1 1 2 2 ? 1 3 1 1 1 1 ? 2 2 1 2 2 1 1 1 1 i 1 1 1 1 0/1 1 3 1 1 1 1 1 1 i 1 1 1 1 1 2 1 1 0/2 2 2 1 2 1 1 1 1 2 1 1 1 2 1 2 1 2 1 1 1 1 2 1 1 1 2 1 2 1 2 1 1 1 1 1 1 1 0/1 1 2 1 1 1 ? ? 9 9 1 2 1 ? 1 1 1 2 1 2 ? 2 2 1 1 1 0/1 1 1 2 2 1 2 1 1 1 2 1 1 1 1 2 2 1 1 2 1 2 1 1 1 2 1 1 1 1 2 2 1 1 ? 1 1 1 1/2 1 1 2 2 1 1 1 1 1 2 ? 1 1 1 2 1 1 1 1 1 1 1 1 1 1 2 1 1 1 0/1 0/1 1 1 2 1 2 2 1 1 1 9 1 2 1 1 1 1 1 1 1 2 2 1 2 1 2 2 2 1 2 1 1 1 1 2 1 2 1 1 2 1 0/1 2 2 1 1 1 2 2 2 1 1 2 1 2 2 1 2 1 1 2 1 1 1 3 2 1 1 1 1 2 1 1 1 1 2 1 1 1 2 1 1 1 2 2 1 2 1 1 1 1 1 1 1 2 1 2 2 1 1 1 1 1 1 1 1 1 1 1 2 1 1 2 2 1 1 2 1 1 1 1 1 1 2 1 1 0/2 1 1 1 1 1 1 1 1 1 1 2 1 2 1 1 1 1 2 1 1 1 1 2 0/1 1 3 i 9 9 9 9 9 9 1 2 1 1 3 1 2 1 3 ? 1 3 i 1 1 2 1 1 3 1 2 1 3 1 1 0/2 3 i 7 9 9 9 9 ? 1 1 1 1 3 1 2 1 3 ? 2 3 1 1 2 1 2 1 2 2 2 2 1 3 1 3 1 1 1 1 1 1 1 1 1 1 1 2 1 1 1 1 2 1 1 2 1 1 1 1 2 1 1 1 1 1 3 2 2 2 1 ? 1 1 1 1 1 1 3 1 0/2 1 1 1 1 1 1 1 2 1 2 1 1 2 1 1 1 2 1 1 2 2 0/1 2 2 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 1 1 1 1 1 1 ? 1 1 1 1 1 1 1 2 1 1 1 2 1 1 1 1 2 1 1 1 1 2 ? ? 1 2 1 1 1 1 1 1 1 2 1 0/1 1 1 1 1 2 2 1 1 2 1 1 3 2 1 1 1 2 1 2 1 1 1 2 1 1 2 1 1 1 1 2 1 1 1 2 1 1 1 2 1 1 2 1 1 1 1 1 1 1 2 1 1 2 1 2 1 1 1 1 1 2 1 1 2 1 1 1 1 1 1 ? 1 0/1 2 1 1 1 1 2 1 1 1 1 1 2 1 1 1 1 1 1 1 1 1 2 1 1 1 1 1 1 1 1 1 1 verse among phyllotines and are present in Aulis- comys, Euneomys, Irenomys, Neotomys, and Reithrodon. Grooves are not found among other New World muroids except for Sigmodon alstoni and the neotomine-peromyscine Reithrodonto- mys. Fine, not always consistent striae are found in Auliscomys boliviensis. The other two species of Auliscomys, sublimis and pictus, exhibit fine, shallow grooves, although those of sublimis (Fig. 9A) are less pronounced than those of pictus (Fig. 9B) and usually require magnification to identify. The grooves in Euneomys (Fig. 9C) are distinct, while those of Irenomys (Fig. 9D) and Reithrodon (Fig. 9E) are still more pronounced and easily vis- ible to the naked eye. The grooves in Neotomys (Fig. 9F) are the most developed, being invagi- nated with a prominent valley retained on the la- bial corner of the tooth. The position of the grooves STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 15 Table 4. Continued. 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 Thomasomys baeops 2 1 2 1 3 7 1 1 1 1 1 3 Ichthyomys hydrobates 2 1 7 1 1 Holochilus brasiliensis 3 ? 1 1 7 2 1 3 Nectomys squamipes 3 1 2 1 1 1 1 1 Pseudoryzomys simplex 3 1 1 1 1 1 1 1 2 1 Zygodontomys brevicauda 3 1 1 1 1 1 1 1 1 1 Akodon albiventer 1 3 1 1 1 1 2 3 Akodon boliviensis 1 1 2 1 2 3 Chroeomys andinus 1 2 1 1 2 1 3 1 Oxymycterus hispidus 2 1 1/2 1 1 1 1 3 Scapteromys tumidus 1 1 2 1 1 7 1 0/1 9 2 1 2 Punomys lemminus 2 1 1 ? 2 1 1 1 1 1 2 2 1 Calomys callosus 3 1 1 1 1 2 1 3 Calomys hummelincki 3 2 7 1 1 1 2 1 3 Calomys laucha 3 1 2 1 2 1 3 1 Calomys lepidus 2 1 2 3 2 1 1 3 Calomys sorellus 2 2 2 2 1 3 1 Andalgalomys pearsoni 3 0/1 2 1 2 7 2 1 1 3 1 1 Graomys domorum 3 2 1 3 2 1 3 1 1 Graomys griseoflavus 3 2 1 2 2 1 3 1 1 Eligmodontia morgani 2 2 3 2 1 1 3 1 Galenomys garleppi 2 2 2 2 1 3 1 Auliscomys boliviensis 2 1 3 2 1 3 1 Auliscomys pictus 2 1 7 2 2 1 1 3 1 Auliscomys sublimis 1 0/1 1 2 2 1 3 1 Euneomys chinchilloides 2 2 2 1 1 2 1 3 1 Euneomys petersoni 2 2 2 1 1 2 1 3 1 Reithrodon auritus evae 2 1 2 1 3 2 2 2 4 2 Reithrodon auritus pachycephalus 2 1 2 1 3 7 2 2 2 4 1 Reithrodon typicus 2 1 2 1 3 7 2 2 2 4 1 Neotomys ebriosus 2 1 0/1 1 2 1 1 2 2 2 3 3 Loxodontomys micropus 1 2 2 2 3 1 Irenomys tarsalis 2 1 1 1 2 3 1 1 3 3 Andinomys edax 2 1 2 1 1 2 2 1 1 2 1 1 3 3 Chinchillula sahamae 2 1 1 1 2 2 1 1 1 3 2 Phyllotis amicus 2 2 2 3 2 1 3 1 Phyllotis andium 2 2 1 3 2 3 1 Phyllotis caprinus 2 2 2 2 2 3 1 Phyllotis darwini 2 1 2 2 2 2 3 1 Phyllotis definitus 2 2 2 3 2 1 3 1 Phyllotis gerbillus 2 2 1 3 1 2 3 1 Phyllotis haggardi 2 2 1 3 2 2 3 Phyllotis magister 2 2 1 3 2 3 1 Phyllotis osilae 1 2 2 3 7 2 2 3 1 Phyllotis wolffsohni 3 2 1 2 1 1 3 1 Phyllotis xanthopygus rupestris 2 2 1 2 1 2 3 1 Phyllotis xanthopygus xanthopygus 2 2 2 2 1 2 3 1 on the incisors is down the middle of the tooth, with two exceptions. Pearson and Christie (1991) found that the position of the groove, either medial or positioned asymmetrically toward the lateral margin, distinguished two species of Euneomys. In Neotomys, the groove is shifted to the lateral margin, leaving the anterior surface of the tooth smooth and slightly concave. 2P. Incisor Procumbency— 4 states. = hyper-opisthodont 1 = opisthodont 2 = orthodont 3 = proodont Upper incisor procumbency is usually subdi- vided into three categories (e.g., Hershkovitz, 1 962, 16 FIELDIANA: ZOOLOGY Table 4. Continued. 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 1 1 2 ? 2 2 ? ? ? 1 1 1 2 9 9 7 9 9 9 1 2 ? 2 2 1 ? 7 ? 1 ? 2 2 1 1 1 1 2 ? 2 ? ? ? ? ? 1 ? 2 1 ? ? 1 1 2 ? 1 2 2 1 ? 2 1 ? ? 1 2 7 0/2 1 1 7 ? ? ? 1 1 ? ? 7 ? ? 1 1 1 7 1 2 2 1 1 ? ? 1 2 1 2 1 1 1 ? ? 1 2 2 1 1 1 2 ? ? ? 1 1 2 0/2 1 1 1 1 1 1 9 9 9 9 9 9 1 2 ? 1 7 ? ? ? 2 1 2 1 1 1 ? ? ? ? 2 1 1 1 7 ? ? ? 2 1 7 ? 2 1 ? ? ? ? 1 1 1 1 1 ? ? 2 1 1 1 ? ? ? 1 1 0/1 1 1 1 1 1 1 1 ? ? 1 1 1 1 ? ? ? ? 1 1 9 9 9 9 9 9 1 1 0/2 1 ? 1 1 1 1 ? ? ? 1 2 1 1 1 2 1 ? ? ? ? ? 1 1 1 1 ? 1 1 1 1 1 1 ? 1 1 2 1 2 ? ? ? 1 7 ? ? ? 2 1 1 1 1 2 1 2 7 ? ? 1 1 ? ? ? ? ? 1 1 1 1 2 1 2 1 1 1 1 1 ? 2 1 1 2 1 2 1 1 1 2 1 ? 2 1 ? 2 1 2 1 1 1 ? 1 ? 2 2 2 9 9 9 9 9 9 1 1 1 1 1 ? 1 1 2 ? ? ? 1 1 1 1 1 ? 2 1 1 1 2 1 1 ? ? 1 2 1 1 ? 1 2 ? 1 1 1 1 1 1 1 1 1 1 1 9 9 9 9 9 1 1 1 7 1 1 1 1 1 1 1 1 ? 7 7 ? ? 1 1 1 2 2 ? 2 1 ? ? 7 1 1 7 2 ? 2 1 ? ? 2 ? 1 1 2 2 ? 2 1 ? ? 1 1 1 ? 1 1 1 2 1 1 1 2 2 7 2 ? ? ? 7 ? ? 1 1 ? 7 1 ? 7 ? ? ? ? ? ? 1 1 1 1 1 7 2 1 1 2 1 1 ? ? 2 1 1 7 0/1 1 1 1 1 1 1 ? ? ? 1 7 2 2 1 1 1 2 1 7 2 1 1 1 1 1 2 1 1 2 7 7 ? ? ? 1 7 1 0/1 ? ? 1 2 1 2 ? 1 1 2 1 2 7 ? ? ? 1 2 1 1 2 1 2 1 1 1 1 2 1 1 1 2 ? 7 ? 1 1 2 1 1 7 ? 1 2 2 1 1 1 1 2 1 ? 2 1 2 1 ? ? ? 7 ? 7 1 1 1 1 1 7 ? ? 1 2 1 1 ? ? 1 1 2 ? ? 2 1 1/2 ? ? ? ? 1 1 1 1 ? ? ? ? 1 1 7 ? ? 1 ? 1 1 1 1 2 1 1 2 7 1 1 2 2 1 1 1 1 1 1/2 ? 1 1 1 2 1 1 1 ? ? ? 2 2 1 1 1 2 2 1 1 2 ? 2 2 1 1 1 1 2 1 1 ? 7 Fig. 19): opisthodont (recurved), orthodont, and proodont (extended forward). Because of the di- versity of opisthodont forms among phyllotines, this category was further divided into opisthodont and hyper-opisthodont. The categories are defined by the position of the cutting edge of the incisor relative to the vertical-incisive plane. The vertical- incisive plane passes through the anterior alveolar border and is perpendicular to the basal-incisive plane. In proodont teeth, the cutting edge lies an- terior to the vertical-incisive plane. In orthodont teeth the cutting edge lies along the vertical-inci- sive plane, while in opisthodont and hyper-opis- thodont teeth it lies posterior to the plane. Hyper- opisthodont teeth are distinguished from opistho- dont teeth by the cutting edge lying posterior also to the posterior alveolar border of the incisor. Proodont incisors are not found in any phyllotine, STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 17 max srz jug sqm soc FIELDIANA: ZOOLOGY but this observation depends on how much vari- ation is subsumed within the orthodont category. Hershkovitz (1962) described A. boliviensis and Galenomys as having proodont incisors, but my observations of many of the same specimens that he examined led me to categorize them as ortho- dont, as are A. sublimis and A. pictus. The lower incisors of Galenomys are also highly proodont, and Hershkovitz (1962) reported that Galenomys is more pronounced in this regard than any other "cricetine." Most of the remaining phyllotines have opis- thodont incisors. Hyper-opisthodont incisors are limited to C. callosus and C. laucha, Eligmodon- tia, Reithrodon, Neotomys, Irenomys, and Loxo- dontomys. 3 P. Upper Incisor Dentine Fissure - (Fig. 10). 3 states = long straight slit 1 = short, not quite linear slit, "comma"-shaped 2 = tripartite, "Y"-shaped In most phyllotines and other sigmodontines, the dentine of the incisor is cleaved anteroposteri- orly into a long, straight slit (Fig. 1 0C). Members of the Reithrodon, Auliscomys, and Andinomys generic-groups are characterized by modifications of this condition. The genera Auliscomys, Chin- chillula, Galenomys, and Irenomys show a shorter slit that becomes rounded or "comma"-shaped at the anterior end (Fig. 10B). This condition can also be found in P. definitus and in some speci- mens of P. wolffsohni. In the third condition, the anterior end splits in two, becoming tripartite or "Y"-shaped (Fig. 10A). This condition is found in the Reithrodon generic-group, in Loxodonto- mys, and in northern Andinomys edax. The tri- partite condition is best developed in Loxodon- tomys and has not been observed by me outside the phyllotines. This trait often shows some vari- ability within species (most notably in Andinomys, which exhibits both states "0" and "2"), and wear patterns can make it difficult to determine whether the straight or "comma"-shaped condition is pres- ent. 4P 5P. Labial Root of Ml characters. •4 states, 2 sub- 00 = absent 10 = present, small, set medially 20 = present, medium to large, set laterally ?1 = 2 lateral roots The character states and transition series match Carleton (1980) with the exception that Carleton hypothesized that two lateral roots were derived directly from roots absent, while I allow two roots to be derived from any of the states in a single step. Carleton hypothesized the absence of labial roots to be plesiomorphic for neotomine-pero- myscines, but a large lateral root is the widespread and possibly plesiomorphic condition among phyllotines. Auliscomys and Andinomys have a small medial root, while Euneomys, Neotomys, and Irenomys lack it altogether. The condition in Loxodontomys is unclear because it possesses a second root along the lateral border, which may be a modification of the primitive condition. Molar Roots of M2— Not coded. The wide- spread condition among phyllotines is a single large lingual root in addition to the anterior and pos- terior roots. Reithrodon auritus pachycephalus and possibly Euneomys chinchilloides have a partially bifurcated lingual root. The condition in other spe- cies of those genera is not known. Chinchillula lacks the lingual root entirely, consistent with the general reduction in the number of molar roots in that genus. 6P. Molar Roots of M3 — 3 states. = 3 roots 1=2 roots 2 = 1 root Phyllotines show one, two, or three roots in the third upper molar, with three roots the common condition. Carleton (1980) considered three roots to be plesiomorphic for the neotomine-peromys- cines. Reduced numbers occur in Andinomys, Chinchillula, Loxodontomys, A. boliviensis, Phyl- lotis gerbillus, P. darwini, and P. xanthopygus. All these examples have two roots except for Chin- chillula, which has the most highly derived con- dition of a single root. 7P. Labial Root of m! — 2 states. Fig. 6. Dorsal view of a generalized Phyllotis cranium, ab, antorbital bridge; fr, frontal; ip, interparietal; jug, jugal; lc, lachrymal; max, maxillary; mrz, maxillary root of zygomatic arch; nas, nasal, nlf, nasolacrimal foramen; par, parietal; pre, premaxillary; soc, supraoccipital; sqm, squamosal; srz, squamosal root of zygomatic arch; zn, zygomatic notch. STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 19 20 FIELDIANA: ZOOLOGY = absent 1 = present Carleton ( 1 980) considered absence of the labial root to be plesiomorphic for the neotomine-per- omyscines, but the presence of a labial root is the widespread condition among phyllotines. Only Euneomys, Neotomys, and Irenomys lack this root. These are the same species that lack the labial root on M 1 . The intermediate condition found in some Mis (presence of a small, medially positioned root) is not observed in the ml of any phyllotine. 8 P. Molar Roots of m2— 2 states. = 2 roots 1 = 3 roots Three roots is the widespread condition, again in apparent contrast to Carleton's (1980) hypoth- esis that two roots was plesiomorphic for the neo- tomine-peromyscines. The derived reduced state is again found in Euneomys and Irenomys, but not in Neotomys. Two roots are also found in Andi- nomys, Auliscomys, and Loxodontomys as well as P. magister, P. haggardi, and P. wolffsohni. How- ever, sample sizes are usually one or two, so in- dividual variation is difficult to p^sess. 9P. Molar Roots of m3 — 2 states. = 2 roots 1 = 3 roots Again, the widespread state among the phyllo- tines is for the full complement of three roots. Two roots were found in Andalgalomys, Eligmodontia, Galenomys, and Neotomys. It is unknown if three roots are found in the unexamined species of An- dalgalomys and Eligmodontia. 10P. Anteromedian Flexus Ml— 4 states. = absent or limited to shallow groove 1 = distinct or prominent 2 = infolded to form lake 3 = loss from state "2," with reduction of lake Character states "0" and "3" are difficult to dis- tinguish because both represent absence of the an- teromedian flexus but are at opposite ends of the transformation series. In some outgroup taxa that superficially appear to lack the anteromedian flex- us (e.g., Pseudoryzomys, Zygodontomys), the rem- nant enamel island from a fully infolded and cutoff flexus can be seen in relatively unworn teeth. Cut- off flexi can also be clearly seen at all ages in many oryzomyines. There is thus the distinct possibility that the absence of an anteromedian flexus could be a secondary loss from a derived, infolded con- dition rather than from reduction of the flexus depth. Additionally, enamel islands, sometimes connected to the flexus, can be seen in slightly worn teeth of some phyllotine species. The con- dition for species lacking this ontogenetic infor- mation is conservatively coded as unknown, "?". A distinct anteromedian flexus is found in An- dalgalomys, Calomys, Galenomys, and Aulisco- mys pictus. IS. Mesoloph(-id)— 3 states. = mesoloph(-id) joined with mesostyle(-id): (pentalophodont) 1 = small mesoloph or mesolophid present, does not join with mesostyle(-id), or partially fused with paracone 2 = absent: (tetralophodont) Hershkovitz ( 1 993) pointed out the potential for mistaking a paralophule (arising from the para- cone) with a mesoloph (arising from the mure). Mesoloph is weakly developed in some akodon- tines and Anotomys and usually partially fused to paracone when present; there may be either a well- developed mesoloph or paralophule in Scaptero- mys (a partially fused mesoloph seems most likely). Among sigmodontines, complete mesolophostyles (mesoloph fused with the mesostyle) are found only in oryzomyines and thomasomyines. The pentalophodont condition is conventionally hy- pothesized to be plesiomorphic (e.g., Hershkovitz, 1962, 1966b, 1993; Carleton, 1980). However, placement of the root to the sigmodontine tree can strongly affect this polarity assignment. Mesolophs are entirely absent in phyllotines and most ich- thyomyines. Enteroloph, Ectolophid— Not analyzed. The absence of an enteroloph or ectolophid was listed Fig. 7. Ventral view of a generalized Phyllotis cranium, als, alisphenoid; boc, basioccipital; bsp, basisphenoid; cc, carotid canal; ect, ectotympanic part of auditory bulla; fm, foramen magnum; fo, foramen ovale; if, incisive foramen; max, maxillary; mlf, middle lacerate foramen; mpf, mesopterygoid fossa; mpi, medial process of incisive foramen; ms, mastoidal capsule; occ, occipital condyle; pal, palatines; pet, petrosal part of auditory bulla; pi, pos- terolateral palatal pit; ppf, parapterygoid fossa; ppp, parapterygoid process; pre, premaxillary; psh, presphenoid; sf, stapedial foramen; spv, sphenopalatine vacuity; sqm, squamosal; sts, stapedial spine of auditory bulla. STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 21 Fig. 8. Lateral view of a generalized Phyllotis cranium, ab, antorbital bridge; als, alisphenoid; ect, ectotympanic part of auditory bulla; fo, foramen ovale; fr, frontal; hp, hamular process of squamosal; ip, interparietal; jug, jugal; max, maxillary; ms, mastoidal capsule; nas, nasal; nlf, nasolacrimal foramen; of, optic foramen; par, parietal; pfg, postglenoid foramen; ppp, parapterygoid process; pre, premaxillary; soc, supraoccipital; spf, sphenopalatine foramen; sqm, squamosal; ssf, subsquamosal foramen; sts, stapedial spine of auditory bulla; tt, tegmen tympani; zp, zygomatic plate; zs, zygomatic spine. by Olds and Anderson (1989) as a possible phyl- lotine synapomorphy, but they chose not to in- clude it in the diagnosis. Olds and Anderson implied that it shows a parallel pattern to the mesoloph(-id) and cited Carleton's (1980) general concept of the derived and concerted simplifica- tion of various enamel structures. However, while most sigmodontines have a mesoloph(-id), among surveyed species only Punomys has a distinct en- teroloph and ectolophid. It is therefore phyloge- netically uninformati ve within the context of this study. 1 IP. Mesostyle Ml —2 states. = absent 1 = present A small mesostyle on the labial border, uncon- nected to a mesoloph, is found in Calomys and Chinchillula. All other phyllotines lack the me- sostyle. 1 2P. Parastyle/Anteroflexus M 1 — 3 states. = absent 1 = present, indistinct 2 = present, distinct An indistinct parastyle and shallow anteroflexus are found in Calomys and Loxodontomys and may be plesiomorphic for the phyllotines. Both are ab- sent in C. sorellus and all remaining phyllotines. The problematic Punomys has a well-developed parastyle. 13 P. Flexus Penetration Ml— 3 states. = flexi from opposite sides do not reach each other 1 = enamel overlaps, or flexi meet at midline 2 = flexi cross beyond each other This character varies strongly with age, and the characterizations here are for adults with moder- ately worn teeth. Wear reduces the apparent pen- etration, so that in many taxa (e.g., Phyllotis), the flexi of well-worn molars do not overlap. Taxa with highly involuted molars, the "sigmodont" condition of Hershkovitz (1955), include Euneo- mys, Reithrodon, and Neotomys. Less strongly in- voluted but still overlapping flexi are found in Graomys and Loxodontomys. Nonoverlapping flexi occur sporadically among the phyllotines and can be found in species of Calomys, Phyllotis, Andal- galomys, Eligmodontia, and Auliscomys in addi- tion to some of the monotypic genera. 1 4P. Anterolabial Cingulum m 1 — 3 states. = anterolabial cingulum absent 1 = anterolabial cingulum weakly developed, lost with wear 2 = anterolabial cingulum distinct A distinct anterolabial cingulum that is present at all ages is the common condition in phyllotines. There is considerable variation in length and width that is discussed under protoflexid. Variation is also associated with the size, shape, and overall 22 FIELDIANA: ZOOLOGY I / Fig. 9. Variation in incisor grooves among phyllotines; pointers identify grooves. A, Auliscomys sublimis (fmnh 10771 1); B, Auliscomys pictus (fmnh 64344); C, Euneomys chinchilloides (fmnh 50600); D, Irenomys tarsalis (fmnh 124057); E, Reithrodon auritus (fmnh 134228); F, Neotomys ebriosus (fmnh 24777). Fig. 10. Upper incisor dentine lake. A, tripartite, Loxodontomys micropus (fmnh 23237); B, curved, Irenomys tarsalis (fmnh 133164); C, straight, Graomys griseoflavus (fmnh 50923). STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 23 complexity of the procingulum. Reduction of the anterolabial cingulum occurs in Andalgalomys, Eligmodontia, Auliscomys, Reithrodon, and Neo- tomys, while it is completely absent in Euneomys. 15P. Protoflexid Ml— 2 states. = short anterolabial cingulum, which may curl toward protoconid; simple protoflexid 1 = long anterolabial cingulum, fusing with pro- toconid and leaving protoflexid as lake A medium to short anterolabial cingulum that may curve toward the protoconid but that does not fuse is widespread among sigmodontines and thus appears to be plesiomorphic for the phyllo- tine. In the derived condition, which was not ob- served in the outgroups, the anterolabial cingulum is very long and fuses with the protoconid at least basally, leaving the protoflexid as a lake. The de- rived condition is found in all Phyllotis, C. sorellus, Chinchillula, Galenomys, A. sublimis, and Gra- omys. The protostylid may be made distinct by a pinching of the cingulum proximally or may be unrecognizable within the gradual thinning of the anterolabial cingulum. The protoflexid lake is most pronounced in almost all species of Phyllotis. 1 6P. Cusp Arrangement m 1 — 3 states. = primary cusps opposite in position 1 = primary cusps intermediate 2 = primary cusps alternate Primary cusps can be positioned so that the la- bial and lingual pairs are each opposite each other, with no anterior or posterior shift. In the alternate arrangement, the metacone is situated across from the hypoflexid, produced by a posterior shift of the lingual conids relative to the labial conids. Carleton (1980) tentatively hypothesized opposite cusps as plesiomorphic, but the intermediate con- dition is most widespread among the phyllotines. Opposite cusps are found in Euneomys, Irenomys, and Loxodontomys. Close attention to ontogenetic series is needed to verify cusp homology among the "sigmodont" genera in order to score this char- acter. 17P. Anteromedian Flexid Ml — 3 states. = absent or limited to shallow groove 1 = prominent 2 = infolded to form lake, which may be lost with wear Variation in this trait parallels that in M 1 . Ad- dressing the oryzomyines where the lake is highly developed, Voss and Carleton (1993) described the lake as an "internal enameled pit" and cited the same uncertainties as I do; they did not hy- pothesize an ancestral condition. Carleton (1980) considered the absence of the flexid (undivided anterocone) to be primitive, but at a much more inclusive taxonomic level. The taxonomically scattered occurrence of a faint remnant of the lake in young individuals of some Graomys, Phyllotis, and Auliscomys raises the likelihood that the ob- served absence in most Phyllotis and Auliscomys is a secondary loss. Many of the species, particu- larly most Phyllotis, have been coded as unknown to reflect that uncertainty. Prominent anterome- dian flexids are found in most Calomys, Andi- nomys, and P. gerbillus. An infolded lake is found in Euneomys, Reithrodon, and Irenomys. 18P. Procingulum Separation Ml— 2 states. = procingulum attached by anterior mure 1 = procingulum separated, mure cut by oppos- ing flexids The procingulum in Euneomys (Fig. 40D) is en- tirely separate from the primary cusps by the ab- sence of a connecting mure. This condition persists even in highly worn teeth. This trait is unique to Euneomys among the phyllotines and among all examined sigmodontines. The separation of the procingulum in the fossil Bothriomys was presum- ably important to Hershkovitz's decision to syn- onymize it with Euneomys (Hershkovitz, 1962). However, the procingulum is distinctly triangular in Bothriomys, similar to Reithrodon and Neoto- mys, rather than the equally distinct round pro- cingulum in Euneomys. 1 9P. Posterolophid/Stylid m 1 — 3 states. = absent 1 = intermediate, posteroflexid present as groove, or obvious in juvenile, absent with strong wear 2 = distinct at all ages The posterolophid is never highly developed and large in phyllotines but ranges from a prominent lophid to absence. The intermediate condition is common, where the posteroflexid may be prom- inent in juvenile teeth but then lost with strong wear. The widespread condition among phyllo- tines is for a prominent lophid to be present at all ages. Posterolophids are entirely absent only in the prismatic molars of Irenomys and Chinchillula. The intermediate condition is found in Andalga- lomys, Galenomys, and all Phyllotis except P. ger- billus, P. amicus, and P. caprinus. 20P. Posterolophid/Stylid m3 — 3 states. = absent 24 FIELDIANA: ZOOLOGY 1 = intermediate, posteroflexid present as groove, or obvious in juvenile, absent with strong wear 2 = distinct at all ages The range of variation among sigmodontines in this structure is largely the same as for ml, al- though in general the third molar is less complex than the first molar. Reflecting this, no postero- lophid is found in most phyllotines. The only ex- ceptions are bud-like posterolophids in Euneomys and the occasional remnant of a posteroflexid in Neotomys. 2 IP. Procingulum M2— 4 states. = absent 1 = anteroflexus appears as groove 2 = protoflexus may appear also; if so, procin- gulum poorly developed as broad, shallow projection with concave anterior edge; if not, then distinct antero- or paraflexus 3 = procingulum distinct, well developed The procingulum on the second molar is phys- ically constrained by the first molar and is much less complex than the procingulum on the first molar. For example, anterior conules are always absent. In phyllotines, it usually appears com- pressed against the first molar. Nonetheless, de- velopment of the procingulum on M2 exhibits rel- atively high variability between individuals of the same species. Complete loss of the anteroflexus and procingulum is found in Irenomys, Chinchil- lula, P. osilae, and P. haggardi. A well-developed procingulum is found in Reithrodon, Neotomys, Loxodontomys, and Andinomys. The comparative presence or absence of accessory anterior or pos- terior lophs is diagnostic among the "sigmodont" genera. Among them, only Neotomys has a pos- teroloph (on M3), and Euneomys lacks the pro- cingulum on both M2 and M3 that is seen in Reith- rodon and Neotomys. 22P. Procingulum m2 — 3 states. = absent 1 = protoflexid appears as groove; if pronounced in juvenile, then wears away with age 2 = procingulum well developed Development of the procingulum on m2 also exhibits relatively high variability among individ- uals of the same species. The common condition for phyllotines is a weakly developed procingulum in which the protoflexid appears as a groove and, if pronounced in juveniles, wears away with age. Absence of a procingulum at all ages is found in Andalgalomys, Auliscomys boliviensis, P. osilae, Euneomys, and Neotomys. The more developed but still bud-like procingulum appears in Ireno- mys and Andinomys. 23P. Hypoflexus Reduction M3— 3 states. = no reduction relative to M2 1 = reduced relative to M2 2 = highly reduced relative to M2, to absent This character and the several following (24-30) describe the complex but subtle variation in the shape of the third molars. General descriptions of shape (e.g., "S"-shape, "C"-shape) were tried ini- tially, drawing from the descriptions in Carleton's (1980) character 5. These generalities, however, did not adequately describe the independent vari- ation among the dental elements, among other things making state determinations problematic. Therefore, shape was broken down into its specific elements so that they could be more precisely de- fined. Although this runs the risk of overinflating the taxonomic importance of potentially interre- lated characters, I did not find objective grounds for reducing the weight of these characters in the analysis. For each multistate character in this group, character states were treated as ordered. 24P. Reduction of Mesoflexus M3 — 3 states. = no reduction relative to M2 1 = reduced relative to M2 2 = highly reduced relative to M2, or absent 25P. Posterior Shift of Mesoflexus M3— 2 states. = no shift relative to M2 1 = posterior shift relative to M2 26P. Hypoflexus Lake M3 — 2 states. = hypoflexus present, no lake 1 = hypoflexus pinched to form lake In some phyllotines, the hypoflexus appears to have been pinched off to form a lake. The hypo- flexus lake is sometimes extended anteroposteri- orly orthogonal to the general orientation of the hypoflexus, as in P. osilae. A hypoflexus lake is found in some Calomys, Euneomys, Graomys do- morum, and all Phyllotis except P. wolffsohni. The widespread condition among sigmodontines and most phyllotine genera is an intact hypoflexus. 27P. Rotation of Flexus Axes M3 — 2 states. = no rotation of hypoflexus and mesoflexus axes relative to M2 1 = axes rotated relative to M2 STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 25 28P. Mesoflexid Reduction m3 — 3 states. = no reduction relative to m2 1 = reduced relative to m2 2 = highly reduced relative to m2, or absent 29P. Anterior Shift of Mesoflexid m3 — 2 states. = no shift relative to m2 1 = anterior shift relative to m2 30P. Posterior Shift of Hypoflexid m3 — 2 states. = no shift relative to m2 1 = posterior shift relative to m2 3 1 P. Fusion of Opposing Flexi in M3 — 2 states. = flexi do not meet 1 = flexi meet, median mure cut The widespread condition among both out- groups (sigmodontines) and phyllotines is for the opposing flexi not to meet at the midline. In Ir- enomys, they meet and the enamel from opposing flexi fuse but remain intact; the flexi are not con- tinuous (Fig. 40). This is the condition for all pairs of flexi and flexids in Irenomys. In three species, Andalgalomys pearsoni and Graomys griseoflavus as well as Andalgalomys olrogi (according to pub- lished photos [Olds et al., 1987]), the opposing flexi in M3 do in fact fuse and become continuous. Graomys domorum is variable for this trait. Most but not all individuals of Graomys griseoflavus exhibit fused flexi. In Andalgalomys, the flexi are fused in M2 as well. 32P. Ratio of M3 Length to Alveolar Length of Molar Tooth Row— 3 states. = < 0.205 1 = 0.205-0.25 2 = > 0.25 The occlusal length of M3 was compared to the alveolar length of the maxillary tooth row. Among those taxa with enlarged molars, two classes are recognized: most have moderate molars (< 0.25 tooth row length) while large molars (> 0.25 tooth row length) are found in Irenomys and Neotomys. 2S. Length M3 — 3 states. = < 0.63 length M2 1 = 0.63 to 0.96 length M2 2 = > 0.96 length M2 Character state values were determined using segment-coding with a multiplier of 4. Olds and Anderson (1989) considered an M3 more than half the length of M2 to be diagnostic of the phyllo- tines. My observations of the taxonomic distri- bution of this character disagree with that reported by Olds and Anderson. I find that virtually all sigmodontines (26 of 28 surveyed) possess this condition. The source of this systematic discrep- ancy is unknown but may be due to measurement criteria. They stated that "phyllotines seem broad- ly plesiomorphic in this regard" (p. 62), yet in- cluded it in the diagnosis. 3S. Shape M2 — 2 states. = width < 0.91 length 1 = width > 0.91 length Width was measured at the widest point, rather than the occlusal surface, to avoid variation due to wear. Character state values were determined using segment coding with a multiplier of 4. Gen- eralized gap-coding with a criterion variable of 4 results in the same state definitions. Olds and An- derson (1989) reported that the width in phyllo- tines at the posterior half is 2 / 3 or more of the greatest length of the tooth, in contrast to the nar- rower teeth of oxymycterines, akodontines, scap- teromyines, and ichthyomyines. They suggested that phyllotines probably possess the plesiomor- phic condition. As with the ratio of M3/M2, my survey disagrees: no sigmodontine examined has a tooth narrower than 2 / 3 proportion. Width of the occlusal surface, as was measured by Olds and Anderson (1989), is strongly affected by wear, and these differences in definition and age criteria may account for the differences in coding. Cranium and Mandible 33P. Capsular Projection of Mandible— 2 states. = distinct capsule, or elevation of superior masseteric ridge, usually ventral to the coro- noid process 1 = indistinct or absent In many murids, a distinct capsule forms around the root of the lower incisor; this capsule then projects out from the body of the mandible. This character can vary among individuals, so mod- erate sample sizes are needed for coding. 34P. Height of Coronoid Process— 3 states. = above maximum height of mandibular con- dyle 26 FIELDIANA: ZOOLOGY Fig. 1 1 . Ventromedial process of the mandibular ramus (vmr). A, process distinct, Neotomys ebriosus (fmnh 24775); B, process weakly present, ramus sharply angled, Loxodontomys micropus (fmnh 124393); C, process absent, ramus rounded, Phyllotis andium (fmnh 19468). 1 = subequal 2 = below mandibular condyle Coronoid processes that rise above the maxi- mum height of the mandibular condyle, relative to the basal plane of the mandible, are common among phyllotines and were found among all sur- veyed outgroups. 3 5 P. Anterior Masseteric Ridge Position— 4 states. = anterior edge not formed into a knob, well ventral to dip of diastema 1 = knob slightly below dorsal edge of mandible 2 = knob just reaches dorsal edge of mandible 3 = knob exceeds dorsal edge The anteriormost extent of the masseteric ridge is usually enlarged into a small knob or swelling, and the ridge varies between taxa in its dorsal/ ventral position as well as in anterior/posterior position relative to the mental foramen and the ventral curvature of the diastema. This character is surprisingly stable within species. A knob just below the dorsal edge of the mandible at the di- astema is common among the phyllotines. In Ir- enomys and Andinomys, the knob is below and well posterior to the ventral curvature of the di- astema. The knob just reaches the dorsal edge of the mandible in C. callosus, C. laucha, Andalga- lomys, Graomys, most Phyllotis, Galenomys, and R. auritus. The most extreme condition, which appears derived in reference to its absence among other sigmodontines, has the knob exceeding the dorsal edge of the mandible and is found only in Eligmodontia and P. gerbillus. 36P. = Medioventral Process of Mandibular Ramus— 3 states (Fig. 1 1). process absent, ramus rounded when viewed an- ventrally or not sharply angled 1 = process weakly present, or ramus sharply gled, near 90° 2 = process distinct At the posterior terminus of the symphysis, the ventral surface of the ramus curves so that the two halves of the mandible diverge. The radius of cur- vature at this point is variable among taxa. It rang- es from smoothly curved, to sharply angled (« 90°), to the presence of a distinct pair of processes nearly rejoining at the midline (Fig. 1 1). Greater development of this trait is generally associated with robustness of the jaw. Intraspecific variation STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 27 can sometimes cross over the categorical boundary between smoothly and sharply rounded. The more widespread condition among sigmodontines is smoothly rounded (Fig. 1 1 C). The sharply angled condition (Fig. 1 1 B) is found in G. domorum, the remaining Phyllotis, and all other genera except Neotomys. The condition in Neotomys is further modified into distinct processes (Fig. 1 1 A), diag- nostic for the genus, although some individuals of Andinomys have moderately developed processes. 37P. Premaxillary Protrusion— 3 states. = premaxillaries terminating behind the ante- rior plane of the incisors 1 = premaxillaries terminating at or slightly an- terior to incisive plane 2 = premaxillaries produced well anterior to in- cisive plane This character is defined by the point at which the anterior edges of the premaxillaries terminate relative to the most anterior margin of the upper incisors. This character is structurally associated with incisor procumbency, but most variation ap- pears to be independent of that dental character. 4S 38P. Posterior Extent of Incisive For- amina— 4 states. = not reaching anterior margin of anterolabial and anterolingual conules of M 1 1 = level with anterolabial and anterolingual conules 2 = extending to level of paracone and protocone 3 = extending to level of hypocone and metacone This character is often imprecisely but conve- niently designated as "length" of the incisive fora- mina. Among sigmodontines, foramina that do not reach the first molars are characteristic of the ichthyomyines, many oryzomyines, and some tho- masomyines. Most other sigmodontines exhibit state "1" where the incisive foramina reach the anterior conules. The widespread presence of state "0" ("short foramina") among the outgroups sur- veyed in this study suggests that condition as the plesiomorphic condition for sigmodontines, but Voss and Carleton (1993) considered the plesio- morphic state as unknown. The most extensive foramina are found among some akodontines and phyllotines. The widespread condition among phyllotines is for the incisive foramina to terminate approxi- mately medial to the anterior conules of M 1 . Fora- mina that do not reach the anterior alveoli of the molars are found among phyllotines only in Neo- tomys. Foramina extend to the paracone and pro- tocone in Irenomys, Loxodontomys, Auliscomys sublimis, and A. pictus. Even longer foramina that extend to the hypocone and metacone are diag- nostic of Reithrodon. The fossil Proreithrodon (Roverto, 1914), which was synonymized by Hershkovitz (1955) with Reithrodon, appears to have much less extensive incisive foramina than any living Reithrodon, raising questions about its proper taxonomic placement. 39P. Maxillary Septum of Incisive For- amina— 3 states. = length < '/2 incisive foramina 1 = length Vi-% incisive foramina 2 = length > % incisive foramina The length of the maxillary septum, which is visible in the incisive foramina, can vary inde- pendently of the posterior extent of the incisive foramina. The phyllotines show little variation for this character, with all species surveyed having septa that extend between l h and % the length of the incisive foramina. Calomys hummelincki has septa that may be less than l h the foramina length. Greater variation in this trait occurs outside the phyllotines, where most akodontines have very short septa (< Vi) and most oryzomyines have septa that exceed % the incisive foramina length. 40P. Orientation of Incisive Foramina— 2 states. = separation of anterior apexes < 80% sepa- ration of posterior apexes 1 = separation of anterior apexes 80-100% of posterior apexes Among sigmodontines, the posterior apexes of the incisive foramina are typically more widely set apart than the anterior apexes. Among some phyllotines, the anterior region is more robustly excavated. In Reithrodon, Irenomys, and Andi- nomys, the anterior apexes are separated by a dis- tance between 80 and 100% that separating the posterior apexes. In Neotomys, the anterior apexes are most robust, being as broadly separated as the posterior apexes. 5S41P. DORSO VENTRAL POSITION OF ANTERIOR Root of Zygomata— 3 states (Fig. 12). = antorbital bridge lying well below dorsal sur- face of rostrum ('A-Vi less than rostrum height, as measured from the midpoint between height of zygomatic spine and anteriormost border of orbit) 1 = antorbital bridge below rostrum (displaced < '/» rostrum height) 28 FIELDIANA: ZOOLOGY 2 = insertion high, close on dorsal surface ros- trum (< Vs) or posterior surface of bridge joins at dorsal level of surface In sigmodontines, the anterior root of the zy- gomatic arch rests upon the zygomatic plate, which leans out from the rostrum. The structure con- necting the dorsal surface of the zygomatic plate with the rostrum is the antorbital bridge. The dor- soventral position of the antorbital bridge was measured at the midpoint between the zygomatic spine and the anteriormost margin of the orbit (Fig. 12). The widespread condition among sig- modontines and the likely plesiomorphic condi- tion among phyllotines is for the antorbital bridge to lie well below the dorsal surface of the rostrum, between Vi and Va the depth of the rostrum below the dorsal surface (Fig. 1 2A). This condition char- acterizes Calomys and Andalgalomys, although some individuals off. amicus have low-lying ant- orbital bridges. Most phyllotines have the condi- tion where the antorbital bridge is displaced be- tween Va and V$ the rostral depth below the dorsal surface. A still more extreme condition, where the antorbital bridge lies close on the dorsal surface of the rostrum ( < V» the rostral depth), is found in Chinchillula, Euneomys, Neotomys, Reithro- don, and Auliscomys boliviensis. In Euneomys, the bridge actually inserts onto the dorsal surface of the rostrum (Fig. 1 2B). 6S 42P. Posterior Margin of Zygomatic Plate— 2 states. = anterior to M 1 alveolus 1 = subequal or anterior to alveolus This character was judged by the position of the posterior margin of the zygomatic plate (equiva- lent to the anterior margin of the orbit when viewed ventrally) relative to the anterior alveolus of the first upper molar. Both states are present among "cricetid" outgroups, but state "0" appears to be the more common. 7S. Masseteric Tubercle— 2 states. = absent 1 = present The tendon of the superficial masseter attaches at the bases of the inferior zygomatic root. Among ichthyomyines and to a lesser extent Scotinomys, the point of insertion is on a distinct bony spur (Voss, 1988, Fig. 12) projecting out from the zy- gomatic root, rather than being marked by a patch of rugose bone. Absence of the masseteric tubercle is widespread among New World murids and like- Fig. 12. Position of the anterior root of the zygo- mata, with measurement positions indicated; pms, pre- maxillo-maxillary suture. A, Vi-'/i below dorsal surface of rostrum, Calomys laucha (fmnh 29246); B, inserting high on the rostrum, Euneomys chinchilloides (fmnh 133088). ly plesiomorphic (Voss, 1988). The only other tax- on identified with a masseteric tubercle is the per- omyscine Megadontomys (Voss, 1988). 8S. Zygomatic Notch— 3 states. = absent 1 = shallow, depth < Vi width of notch, and notch less than half length of zygomatic plate 2 = deep, well developed Carleton (1980) concluded that an absent or barely described zygomatic spine was the primi- tive condition for North American neotomine- peromyscines and other nonsigmodontine muroid rodents, and Olds and Anderson (1989) cited STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 29 Carleton (1980) as justification for their polariza- tion of "no notch" as primitive in phyllotines. However, Carleton's observation is weakly infor- mative for phyllotine systematics without a strong phylogenetic hypothesis. Carleton's character 25 actually referred to both the zygomatic notch and zygomatic spine, with emphasis on the spine, not the notch. He viewed these two aspects of the max- illary root of the zygomata as highly correlated, in a data set dominated by neotomine-peromys- cines. However, within the phyllotines, as an ex- ample, the spine (which defines the anterior por- tion of the notch) can vary greatly between relatively closely related species with little varia- tion in the posterior development of the notch. The development of the spine is primarily con- trolled by the degree of excavation of the ventral body of the zygomatic plate, in addition to the overall breadth of the plate. These two aspects of the zygomatic plate need to be distinguished when discussing the sigmodontines. Deep notches are found in most sigmodontines except ichthyomy- ines, many thomasomyines, and some oryzo- myines. 43P. Development of Zygomatic Spine— 4 states. = absent, anterior border of zygomatic plate rounded or receding dorsally 1 = absent, anterior border nearly flat, vertical 2 = moderate, anterior border weakly curved 3 — strongly developed, pronounced concavity The range of variation for this character in the phyllotines equals or exceeds that found among all other sigmodontines. The length of the spine is influenced by the width of the dorsal region of the zygomatic plate and the degree of excavation in the ventral body of its anterior border (see Fig. 8). Voss and Carleton (1993) considered a non- spinous plate to be primitive for sigmodontines, and the common condition among sigmodontines surveyed in this study is for the anterior border of the zygomatic plate to be flat and oriented nearly vertically. Flat margins of the zygomatic plate or weakly developed spines are the widespread con- ditions among phyllotines. Zygomatic spines are most developed in Reithrodon, where their length is greater than the width of the zygomatic plate at the plate's narrowest point. Auliscomys, Chin- chillula, and Galenomys lack spines and have a reduced dorsal body of the zygomatic plate, pro- ducing a convexly rounded anterior border that recedes dorsally (e.g., Fig. 34). 44P. Inclination of Zygomatic Plate— 2 states. = < 20° (in frontal view) 1 = > 20° The lateral inclination of the zygomatic plate out from the rostrum varies moderately among phyllotines (~ 10—40°) but also shows significant variation within species. Zygomatic plates that are inclined greater than 20° from the vertical are widespread among sigmodontines and most likely plesiomorphic for the phyllotines. 45P. Premaxillo-Maxillary Suture Orienta- tion— 2 states. = 90-135° angle formed relative to palatine plane by the suture on the lateral surface of rostrum and below antorbital foramen 1 = suture nearly horizontal at ventral end, sharply angled {> 90°) in middle of rostrum In most phyllotines and all other sigmodontines, the premaxillo-maxillary suture on the side of the rostrum is oriented essentially dorsoventrally and forms a 90-1 35° angle with the ventral edge of the rostrum as it passes around to the ventral side. Euneomys, Neotomys, and Reithrodon are the only sigmodontine genera possessing a suture that makes a sharp bend (> 90°) in the middle of the rostrum and is nearly horizontal when it passes around to the ventral side (Fig. 1 2). The extinct Proreithro- don (Ameghino, 1 908) does not appear to possess this clearly derived condition. 9S 46P. Posterior Extension of Nasals — 2 states (Fig. 1 3). = posteriormost terminus lies clearly posterior to the dorsal maxillary-frontal suture at its contact with the lachrymal 1 = terminus lies subequal with or anterior to the maxillary-frontal suture The extension of the nasals was evaluated against the point at which the maxillary-frontal suture, running along the dorsal surface of the rostrum, reaches the edge of the rostrum and contacts the lachrymal. Nasals often extend further in adults than in juveniles, but ontogenetic variation among adults does not seem significant. The nasals do not extend posterior to the suture contact (Fig. 13 A) in most "cricetid" outgroups, except some Old World "cricetids." Within the sigmodontines, oc- currence of "long" nasals (Fig. 1 3B) is scattered, with both conditions being found within several tribes. "Long" nasals are widespread among phyllo- tines, with shorter nasals limited to Graomys and Reithrodon. 30 FIELDIANA: ZOOLOGY m W v/ nas KjC- •' . max ^s ,c \^ pre '4 / fi ft?' / Civ" ■*' /if ''■ f ¥ \ •- y • -A fr '%\ Jr \ f par Fig. 13. Dorsal views of interorbital region. A, Nyctomys sumichrasti (fmnh 35185); B, Ichthyomys hydrobates (fmnh 90293). 10S47P. Posterior Extension of Premaxil- laries— 3 states (Fig. 13). = posterior terminus of premaxillaries extends posterior to the terminus of the nasals 1 = terminus of premaxillaries subequal to ter- minus of nasals 2 = terminus of premaxillaries lies anterior to terminus of nasals Premaxillaries that lie anterior to ("shorter" than) nasals (Fig. 13B) were not observed among the "cricetid" outgroups, and subequal premax- illaries (Fig. 13 A) were found only in basal neo- tomine— peromyscines. "Long" premaxillaries thus may be plesiomorphic for the sigmodontines. Pre- maxillaries that extend subequally to nasals were found among many oryzomyines, phyllotines, and thomasomyines, with "short" premaxillaries com- mon among other groups. No phyllotine was observed to have premaxil- laries that clearly extended posterior to the nasals. 48P. Nasal Width— 2 states. = less than minimum interorbital distance of dorsal surface of rostrum 1 = greater than or equal to minimum interor- bital distance of dorsal surface of rostrum Narrow nasals, defined relative to the minimum interorbital distance on the dorsal surface of the rostrum, are widespread among the sigmodontines and likely plesiomorphic for the phyllotines. Greatest nasal width exceeds the interorbital con- striction in Andinomys, Auliscomys (except sub- limis), Chinchillula, Euneomys, Galenomys, Ir- enomys, Neotomys, Reithrodon, and some Phyllotis. Most of these genera also have relatively constricted interorbital regions, but expansion of the anterior nasals is obvious. 49P. Interorbital Shape— 3 states. = interorbital ridge anteriorly divergent, nar- rowest region in posterior half 1 = narrowest point of interorbital region cen- trally situated within orbital region, as bounded by the frontals 2 = supraorbital ridge posteriorly divergent, nar- rowest region anterior This character describes the shape of the supra- orbital region and the position of the maximum constriction when viewed dorsally. The wide- spread condition among sigmodontines is where the maximum constriction is situated centrally within the region bounded by the frontals. This condition is sometimes called "hourglass"-shaped STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 31 and was considered plesiomorphic for neotomine- peromyscines (Carleton, 1 980) and sigmodontines (Voss, 1 993). Two modifications of the plesiomor- phic condition can be easily recognized. In one condition commonly seen among other muroid rodents, the maximum constriction is anterior and the supraorbital region diverges posteriorly. An- dalgalomys, Graomys, Eligmodontia, Calomys (C callosus, C. laucha, C. hummelincki), P. gerbillus, and P. amicus share this condition, which is as- sociated with ridged and overhanging supraorbit- als. Another derived condition, where the maxi- mum constriction is situated posteriorly and the supraorbital region diverges anteriorly, is found in Andinomys and two species of Auliscomys, A. bo- liviensis, and A. sublimis. Carleton ( 1 980) combined this and the following character into a single character, "supraorbital shape and temporal ridges." Among species that I surveyed, the two characters are associated in that posteriorly divergent supraorbitals are always overhanging and anteriorly divergent supraorbit- als are not, but multiple combinations were ob- served. 1 IS 50P. Supraorbital Edge— 4 states. = supraorbital region smoothly rounded when viewed in cross-section 1 = weakly angled at edge of dorsal surface, or angled for half the length of the supraorbital region 2 = distinctly angled (~ 90°), but not overhang- ing 3 = sharply angled into overhanging shelf, at least posteriorly The variety of supraorbital morphologies ex- hibited by sigmodontines makes it difficult to pro- vide precise definitions of character states. Olds and Anderson (1989) followed Hershkovitz (1962) in describing the diagnostic condition for phyllo- tines as "supraorbital region never evenly curved in cross section." The edge can vary from smooth- ly rounded, to being distinctly but obtusely angled, to acutely angled into an overhanging shelf. The widespread condition for phyllotines is for the su- praorbital edges to be angled along nearly the en- tire supraorbital region. A possibly derived con- dition where only the posterior region is weakly angled is found in Loxodontomys, A. sublimis, and P. osilae. Care must be taken in scoring the char- acter because the ridge becomes more sharply de- fined with age. The sharply ridged, overhanging condition is found in some Calomys (C callosus, C. laucha, C. hummelincki), Andalgalomys, Gra- omys, and (weakly) P. wolffsohni. The overhanging supraorbital is also characteristic of many oryzo- myines. Because it is unclear which states might be adjacent to overhanging supraorbitals in a transformation series, this character was conser- vatively treated as unordered. 5 IP. Supraorbital Ridge— 2 states. = absent or directed laterally 1 = lateral edges of supraorbital ridged and di- rected dorsally This character distinguishes those supraorbital edges that are raised into dorsally directed ridges from those with no or overhanging ridges. The condition, widespread among sigmodontines and likely plesiomorphic for the phyllotines, is to lack any dorsally directed ridges. Dorsally directed ridges are found in Euneomys, Reithrodon, and Chinchillula. 52P. Supraorbital Knobs— 2 states. = absent 1 = small swellings or knobs on anterior supra- orbital region, just posterior to lachrymal In some phyllotines that otherwise show a slight medial trough along the midline of the supraor- bital region (i.e., similar to weak ridging of the supraorbital edges), bony processes of the frontals are found along the supraorbital margins just pos- terior to the lachrymal bones. Supraorbital knobs are unrelated to the inflated frontals found in oxy- mycterines. The widespread condition is for no such swellings. Supraorbital knobs are found in P. darwini, Andinomys, Euneomys, Neotomys, and Reithrodon. 53P. Mediodorsal Fusion of Frontals — 3 states. = complete 1 = partially open or vascularized 2 = distinct and consistent fontanelle The widespread condition among sigmodon- tines and clearly the plesiomorphic condition for phyllotines is for the frontals to be completely fused along the midline. In Irenomys, Neotomys, and Andinomys, that fusion is not complete for most individuals. In Irenomys and Neotomys, the gap usually is associated with what appears to be a sinus emerging from within the frontals. In some individuals, channels in the bone indicate that a vessel loops up from the frontals and back down into the frontals or cranium. A distinct fontanelle 32 FIELDIANA: ZOOLOGY is present in Andinomys as noted by previous workers (e.g., Hershkovitz, 1962). More than 90% of Andinomys individuals examined (« 50) pos- sess a fontanelle, and several have a second fon- tanelle in the posterior region of the frontals as well. 12S 54P. Shape of Frontoparietal Suture— 2 states (Fig. 13). = rounded, edge of frontal convex 1 = straight or slightly sigmoidal to concave The shape of the frontoparietal suture was eval- uated for the body of the suture, excluding the lateral margins, which usually curve anteriorly to "horn"-shaped extensions of the parietal: the horns are present in taxa exhibiting either condition. Convex, rounded sutures (Fig. 1 3 A) are found in all surveyed outgroups, are widespread among sig- modontines, and thus are likely the plesiomorphic sigmodontine condition. Ichthyomys (Fig. 13B) possesses the more extreme condition where the frontal edge of the suture is concave. Convex sutures are likewise widespread among phyllotines, with the presumptively derived con- dition limited to Andinomys, Chinchillula, Ireno- mys, and Reithrodon. This coding scheme does not apply well to Neotomys, whose frontals are very rounded and sometimes "heart"-shaped, and so Neotomys was coded as unknown. 55P. Angle of Frontoparietal Suture — 2 states (Fig. 1 3). = obtuse angle 1 = acute or right angle The angle was evaluated by judging the orien- tation along the body of the sutures. In cases with strong curvature, particularly near the medial apex, the condition was evaluated by extending lines joining the medial apex to the triple junctures of the frontals, parietals, and squamosals on both sides. In the majority of cases without strong cur- vature, these two criteria are congruent. Obtusely angled sutures (Fig. 13 A) are widespread among sigmodontines and phyllotines and are thus likely plesiomorphic for the phyllotines. This character was not phylogenetically informative among the nonphyllotines surveyed for this study. 1 3S. Ratio of Interparietal/Parietal Length— 3 states. = < 0.43 1 = 0.43-0.70 2 = > 0.70 Character state values were determined using segment-coding with a criterion variable of 4. De- scriptions of interparietal size or shape are often imprecise (e.g., "well developed, at least trans- versely" [Olds & Anderson, 1989], "small, trian- gular, or irregularly oblong" [Voss, 1988]) due par- tially to high intraspecific variability in both attributes. I chose to define one aspect of size and shape as the length of the interparietal relative to the parietal, measured along the midsagittal line. Because this character is variable within most of the recognized tribes as well as in the outgroups, polarity is difficult to determine and easily affected by tree topology. This character appears to be more informative within tribes rather than between. Olds and Anderson (1 989) included a "well developed" interparietal in their differential diagnosis of the phyllotines. They described a well-developed in- terparietal as plesiomorphic for the phyllotines in their character review and thus did not list it with the likely synapomorphies. 56P. Medial Length of Interparietal/Parie- tal— 3 states. - < 0.33 1 = 0.33-0.45 2 = > 0.45 A separate coding scheme was used for the phyl- lotine analysis because the range of variation was less than among the sigmodontines, but taxonom- ically significant variation could still be recog- nized. As with character 1 IS, lengths of the inter- parietal and parietal were measured along the midline. The common condition among phyllo- tines is for a long interparietal (state "2"), but the plesiomorphic condition is unclear with all in- stances of short interparietals among other sig- modontines. A moderate interparietal (between 33 and 45% the medial length of the parietal) is found in most Calomys except C. sorellus, which, like most other phyllotines, has a larger interparietal that is greater than 45% of the parietal length. Moderate interparietals are also found in Aulis- comys and Neotomys. Although not coded in this study because of the difficulty in coding the com- plex variation observed, shape of the interparietal may be a useful character at other taxonomic lev- els. For example, my observations indicate that despite substantial individual variation, particular shapes characterize and distinguish species, sub- species, and even populations within the Phyllotis darwini complex. 1 4S. Parietal/Occipital Contact— 2 states (Fig. 14). STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 33 Fig. 14. Dorsolateral views of posterior cranium. A, parietal and occipital in contact, Nectomys squamipes (fmnh 141633); B, interparietal and squamosal in contact, Nyctomys sumichrasti (fmnh 35186). = parietal and occipital in contact with each other, interparietal and squamosal not in contact 1 = interparietal and squamosal in contact with each other, parietal and occipital not in con- tact The widespread condition seen in sigmodon- tines and outgroups is for the posterolateral mar- gins of the parietal to contact the anterolateral corners of the occipital (Fig. 14 A), even in species with well-developed interparietals. This parietal/ occipital contact may be little more than a milli- meter in length but precludes any contact between the lateral margins of the interparietal and the pos- teromedial corners of the squamosal. Only tylo- myines have interparietals that are broadly in con- tact with the squamosals (Fig. 14B), precluding contact between parietals and occipitals. Neoto- mys is polymorphic for this character, with all four bones nearly meeting at a single vertex. 57P. Orientation of Anterior Border of Auditory Bulla— 3 states. = oblique (viewed ventrally) 1 = transverse 2 = rounded This character largely describes the degree of anterior inflation in the bulla. The widespread condition among sigmodontines is oblique (un- inflated: sloping posterolaterally), but because this condition is so restricted among phyllotines, trans- verse (moderately inflated) may be a phyllotine synapomorphy. An oblique bulla is found in C callosus, Andalgalomys, and some Andinomys. A rounded anterior border to the bulla is found in C. lepidus and many Phyllotis. 15S 5 8 P. Tegmen Tympani— 2 states. = tegmen tympani contacts posterior suspen- sory process of squamosal across middle lac- erate foramen 1 = tegmen tympani does not contact squamosal In most sigmodontines, the tegmen tympani, also known as the periotic portion of the petrosal, crosses the middle lacerate foramen to contact the posterior suspensory process of the squamosal (Voss, 1993, Fig. 8). Voss (1993) and Voss and Carleton (1993) considered this to be the plesio- morphic condition. Voss and Carleton (1993) also proposed that the absence of this contact, and in particular the absence of the suspensory process, is a synapomorphy of the tribe Oryzomyini, but their sample of sigmodontine genera was limited. Absence of the contact was found in all surveyed oryzomyines, including the tetralophodont Hol- ochilus, Pseudoryzomys, and Zygodontomys, in the phyllotine Reithwdon, and in the Old World cri- cetine Mystromys. 34 FIELDIANA: ZOOLOGY 59P. Shape of Stapedial Spine of Auditory Bulla— 2 states (Fig. 15). = circular to ovoid in cross-section 1 = laterally appressed against auditory bulla, not smoothly rounded in cross-section The lateral compression may be a consequence of the high degree of inflation of the auditory bulla in Andalgalomys and Graomys, the only taxa in which this character has been observed (Fig. 1 5B). The stapedial spine is bounded medially and/or laterally by the stapedial artery or its subsidiary branches, the supraorbital and infraorbital. 16S. Squamosal Fold— 2 states. = absent 1 = present The squamosal fold is a thickening along the anterior border of the postglenoid foramen, with the dorsal edge nearly folded over the anterior margin, strongly obscuring a large tegmen tympani and small postglenoid foramen. A squamosal fold has only been observed in Kunsia, Tylomys, and Nyctomys. 17S. Subsquamosal Foramen— 3 states. = present, well developed 1 = reduced to slit, little or no exposure to oc- cipital 2 = absent Carleton (1980) considered the absence of the subsquamosal foramen to be plesiomorphic for New World murids, despite the more widespread occurrence of state "0." The various conditions are dispersed throughout the sigmodontines, but all phyllotines have a well-developed subsqua- mosal foramen. 60P. Thickness of Hamular Process of Squamosal— 4 states. = process wholly absent (i.e., subsquamosal foramen absent) 1 = broad along entire length, subsquamosal fo- ramen often reduced 2 = bridge reduced in thickness, posterior ter- minus appears flattened 3 = posterior end reduced as well, not greatly thicker than bridge The presence and thickness of the hamular pro- cess of the squamosal is dependent on the presence of the subsquamosal foramen. The most frequent condition among phyllotines is for a thin, fragile ^ \ sts c "/ /" M 1^ l\ \ *£ ^ // A Fig. 15. Stapedial process of bulla (sts). A, rounded, Phyllotis xanthopygus (fmnh 20115); B, laterally ap- pressed, Graomys griseoflavus (fmnh 50927). hamular process that widens where it joins the mastoid, thus appearing flattened. The distinction between this state ("2") and one where the pos- terior terminus is thin also and does not appear flattened ("3") does not seem to be taxonomically informative among genera; both states can be found in Calomys, Graomys, Phyllotis, and Auliscomys in nearly equal frequency. A reduced subsqua- mosal foramen and thick hamular process are found in C. callosus and C. hummelincki, as well as in several outgroups. The absence of both fo- ramen and process is found in ichthyomyines and some oryzomyines. 6 1 P. PosrnoNS of Temporal Vacuities — 2 states. = subsquamosal and postglenoid foramina po- sitioned essentially dorsoventrally STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 35 Fig. 16. Medial views of auditory bulla and internal carotid canal. A, internal carotid bounded by both ba- sioccipital and ectotympanic, Phyllotis andium (fmnh 8 1 249); B, internal carotid bounded by petrosal and ecto- tympanic portions of auditory bulla, Neotomys ebriosus (fmnh 24775). boc, basioccipital; cc, carotid canal; ect, ectotympanic part of auditory bulla; pet, petrosal part of auditory bulla; sf, stapedial foramen. 1 = postglenoid foramen distinctly anterior to subsquamosal foramen This character is a simplified description of a complex trait that depends on the orientation and thickness of the hamular process of the squamosal, as well as the size, shape, orientation, and relative positions of the temporal vacuities: the subsqua- mosal foramen and the postglenoid foramen. The anterior extent of each is particularly influential in determining state assignments. The common condition among phyllotines is for the vacuities to be positioned essentially dorsoventrally. The common condition among the outgroups is for the vacuities to be positioned distinctly anteroposte- riorly, with the postglenoid foramen more anterior than ventral to the subsquamosal foramen. This condition is found in C. callosus and C. humme- lincki, Euneomys, Neotomys, Andinomys, and Chinchillula. 62P. Internal Carotid Canal— 2 states (Fig. 16). = bounded by both basioccipital and the ec- totympanic portion of auditory bulla 1 = bounded entirely (or nearly so) by petrosal and ectotympanic portions of auditory bulla The widespread condition among sigmodon- tines and probably the plesiomorphic condition for phyllotines is for the carotid canal to be bound- ed by both the auditory bulla and the basioccipital bone as the internal carotid artery passes between them to enter the braincase (Fig. 16 A). The alter- nate condition differs in having a flange of the petrosal extend between the basioccipital and the internal carotid artery, thus along with the ecto- tympanic portion of the bulla entirely or almost entirely forming the carotid canal (Fig. 1 6B). This condition is found in Andinomys, Chinchillula, Euneomys, Irenomys, and Neotomys. 63P. Extension of Eustachian Tube— 3 states. = tube does not reach posterior lobe of ptery- goid process 1 = tube subequal to posterior lobe of pterygoid process, does not extend anterior to the base of process 2 = tube extends anteriorly past base of pterygoid process The widespread condition among phyllotines and sigmodontines, and most likely plesiomorphic for the phyllotines, is for the anterior flange of the eustachian tube to be subequal with the pterygoid process, reaching the posterior lobe of the process, but not extending anterior to the base of the pro- cess. This is the intermediate state in the transition series represented among the phyllotines. The eu- stachian tubes of many Andinomys have lanciolate projections that can extend up to 2 mm anterior to the bases of the pterygoid processes. 1 8S 64P. Relative Width of Mesopterygoid Fossa— 3 states. = distinctly broader than adjacent paraptery- goid fossae 1 = subequal 2 = distinctly narrower than adjacent parapter- ygoid fossae Previous studies have not always specified a cri- terion for evaluating the size of the two fossae. 36 FIELDIANA: ZOOLOGY This is particularly important because both fossae may converge or diverge posteriorly to different degrees, and thus the relative proportions will vary. Olds and Anderson (1989) evaluated mesoptery- goid breadth at the posterior margin of the zygo- matic aperture. I chose to make the comparison at the basisphenoid-presphenoid suture, believing that this would be a more stable reference land- mark. The different criteria may be the explana- tion for the differences in coding (i.e., Holochilus, Pseudotyzomys). Olds and Anderson (1989) con- sidered that a parapterygoid fossa relatively broad- er than the mesopterygoid fossa was diagnostic for the phyllotines. The condition is variable among sigmodontines, but within the phyllotines the widespread condi- tion is for the mesopterygoid fossa to be distinctly narrower than the parapterygoid fossa. The two fossae are subequal in breadth in Chinchillula, P. wolffsohni, Irenomys, and Andinomys. Broad mesopterygoid fossae are found in several out- group taxa (Holochilus, Nectomys, Oxymycterus, and Zygodontomys). 65P. Parapterygoid Shape— 3 states. = posterior width < 1.5 times anterior width 1 = 1.5-2.4 times anterior width 2 = > 2.4 times anterior width This character describes the degree of posterior divergence in the parapterygoid fossa. The com- mon condition among surveyed sigmodontines and the widespread condition among phyllotines is for the posterior breadth to be 1.5-2.4 times the an- terior breadth. The probably derived condition where the posterior breadth is less than 1.5 times the anterior breadth is found in Euneomys, Lox- odontomys, Neotomys, and Reithrodon. The para- pterygoid fossa diverges more strongly only in P. osilae. 19S. Shape of Mesopterygoid Fossa— 3 states. = posteriorly convergent, "horseshoe"-shaped 1 = parallel sided, "U"-shaped 2 = posteriorly divergent, "V"-shaped The coding of this character for the two analyses differs to reflect the greater range of variation among sigmodontines than among phyllotines. Most outgroups are either convergent or parallel- sided. All phyllotines are divergent, although some are nearly parallel-sided. 66P. Shape of Mesopterygoid Fossa— 3 states. = posterior width < 1.5 times anterior width 1 = 1.5-2.4 times anterior width 2 = > 2.4 times anterior width The categorical values are the same as for the parapterygoid fossa. Here the common condition in phyllotines is a relatively parallel-sided meso- pterygoid fossa ("0")- Moderate posterior diver- gence (1.5-2.4 anterior breadth) is found in Cal- omys lepidus, Andalgalomys, Eligmodontia, and P. definitus. The most posteriorly divergent con- dition is found in Reithrodon. 67P. Parapterygoid Fossa Depth— 3 states. = flat, even with bony palate 1 = slightly to moderately excavated above level of bony palate 2 = deeply excavated above level of bony palate The widespread condition among sigmodon- tines and phyllotines is for a shallow parapterygoid fossa, essentially even with the bony palate. A parapterygoid fossa excavated slightly beyond the level of the bony palate is found in Euneomys and Andinomys. Reithrodon and Neotomys share a well- excavated parapterygoid fossa. Depth and breadth of the parapterygoid fossa may be functionally cor- related with hypsodont grinding molars because the internal pterygoids originate in the parapter- ygoid fossae (Kesner, 1980; Rinker, 1954), and Carleton ( 1 980) accordingly considered a deep fos- sa as derived. 20S 68P. Sphenopalatine Vacuities— 5 states. = absent, roof of mesopterygoid fossa wholly ossified 1 = narrow slit encompassing presphenoid-ba- sisphenoid juncture, wholly visible within mesopterygoid fossa 2 = vacuity distinct but constricted, orbital wings of presphenoid not fully separated posterior to medial pterygoid processes 3 = vacuity large, medial pterygoid processes ful- ly anterior to orbital wings of presphenoid, not visible in mesopterygoid fossa, no large projections of lateral margins into the va- cuity 4 = vacuity very large, orbital wings of presphe- noid filamentous, very large optic foramen The ancestral condition for this character is dif- ficult to determine. All states except the most open vacuities seem to be common among other "cri- cetids." Carleton (1980) considered a wholly os- sified roof of the mesopterygoid fossa to be prim- itive for neotomine-peromyscines, and Olds and Anderson (1989) considered "large" sphenopala- STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 37 tine vacuities (following the description in Carle- ton [1980]) to be a synapomorphy for phyllotines. With the additional character states used in this study, very open sphenopalatine vacuities (states "3" and "4") are only found in the phyllotines and in Sigmodon. Voss (1991) reported significant but discrete variation for this trait among Zygodon- tomys brevicauda. The open sphenopalatine va- cuity that he illustrated for some populations would be categorized as state "2" under my coding scheme rather than state "3," as characterizes the phyl- lotines. Variation in the extent of excavation in the sphenopalatine vacuities is much greater among sigmodontines than within the phyllotines. All phyllotines have large sphenopalatine vacuities that are fully exposed within the mesopterygoid fossa. Reithrodon is characterized by especially large sphenopalatine vacuities in addition to large optic and anterior lacerate foramina. The convergence of the foramina and vacuities in Reithrodon has resulted in filamentous orbital wings of the pre- sphenoid. State "4" is subsumed in state "3" in the sigmodontine analysis because it is represented only in Reithrodon, making it uninformative in the analysis. 69P. Position of Orbital Wings of Presphe- noid— 2 states. = wings anterior to a distinct constriction of the presphenoid 1 = wings posterior to maximum constriction The widespread and almost certainly plesiomor- phic condition in phyllotines is for the wings to join the presphenoid anterior to the sharp con- striction that occurs just anterior to the basisphe- noid. Among phyllotines, the derived condition, where the wings join equal with or posterior to the maximum constriction, is found only in Andal- galomys and Graomys. The derived condition is largely due to the gradual thinning of the presphe- noid in those two genera, rather than the abrupt constriction present in the other phyllotines. 2 IS 70P. Position of Anterior Border of Mesopterygoid Fossa— 4 states. = lying > 1 M3 tooth-length posterior to M3 1 = lying between x h and 1 tooth-length posterior to M3 2 = lying between and < Vi tooth-length pos- terior to M3 3 = reaching posterior plane of paired M3s ("short palate") The position of the mesopterygoid fossa was evaluated relative to the line connecting the pos- terior borders of the upper third molars. This char- acter has sometimes been referred to as "palate length." I used the same criterion for coding "short" palates as did Olds and Anderson (1989), namely, that the mesopterygoid fossa extend anteriorly be- yond the posterior edge of M3, but my observa- tions disagree with their coding ("long" palates) for Ichthyomys, Holochilus, and Neotomys. Hershkovitz (1962) regarded a "short palate" as primitive for the sigmodontines. The widespread condition among phyllotines is for the anterior border of the mesopterygoid fossa to be within Vi to 1 tooth-length (M3) posterior to the posterior alveoli. A shorter palate, with the mesopterygoid fossa within Vi of a tooth-length, is found in some Reithrodon auritus and Chinchil- lula. The mesopterygoid actually reaches the pos- terior plane of the third molars in Irenomys, Neo- tomys, and Andinomys. 7 IP. Medial Process of Posterior Palate— 2 states. = absent 1 = present The common condition among sigmodontines and the phyllotines is for there to be no medial process from the posterior margin of the palate. 72P. Posterior Palatine Ridge— 2 states. = absent or indistinct 1 = present, a longitudinal ridge formed by con- vergence of parallel channels arising from palatine foramina The posterior palatine ridge is a distinct ridge running down the midline of the palate, most pro- nounced posteriorly. It is usually, but not always (e.g., Punomys), continuous with a median process of the posterior palate. The ridge appears to be formed principally by the near coalescence of two channels running along the palate. Among phyl- lotines, the posterior palatine ridge is found only in Reithrodon and Neotomys. 73P. Posterolateral Palatal Pits— 2 states. = anterior to mesopterygoid fossa 1 = posterior to anterior border of mesoptery- goid fossa A pair of pits are always found among phyllo- tines in the posterior region of the palate framing the anterior border of the mesopterygoid fossa. 38 FIELDIANA: ZOOLOGY The widespread condition is for these pits to be just anterior to the mesopterygoid fossa. Alter- natively, the pits are displaced posteriorly into the anterior region of the parapterygoid fossae. This condition is found in Irenomys, Andinomys, and P. osilae. Of these three species, only P. osilae has a "long" palate; that is, two of three phyllotines with pits posterior to the edge of the mesoptery- goid fossa have a mesopterygoid fossa that extends far anteriorly. However, the two traits are not as highly correlated as that observation suggests. Among outgroup taxa surveyed, four out of seven with pits posterior to the mesopterygoid fossa in fact have "long" palates where the mesopterygoid is greater than x h of a tooth-length from the molars. 74P. Orientation of Maxillary Tooth Rows— 3 states. = posteriorly divergent 1 = parallel 2 = convergent The orientation of the maxillary tooth rows is estimated by lines passing through the apexes of the alveoli. Akodontines generally have conver- gent tooth rows, oryzomyines generally parallel, but Punomys has divergent tooth rows. Thus, the plesiomorphic condition for phyllotines is unclear. 7 5 P. Sphenopalatine Foramen— 3 states. = absent or nearly ossified 1 = present, small to moderate size 2 = present, large The common condition among sigmodontines is for the sphenopalatine foramen to be absent or constricted, but the widespread condition among phyllotines is for a distinct and moderate-sized foramen to be present. The constricted condition also occurs in Auliscomys sublimis and Loxodon- tomys. A particularly large sphenopalatine fora- men is found in Reithrodon, consistent with the general high degree of fenestration in its basal cra- nium. 22S 76P. Carotid Circulation— 3 states. = both stapedial and sphenofrontal foramina present, squamosal-alisphenoid groove present 1 = stapedial foramen present, but sphenofrontal foramen absent, no squamosal-alisphenoid groove 2 = both stapedial and sphenofrontal foramina absent, no squamosal-alisphenoid groove Coding largely follows Carleton ( 1 980), who fol- lowed Bugge's (1970) polarity. Readers are di- rected to Bugge ( 1 970) for discussion of the carotid system in muroid rodents and to Brylski (Brylski, 1990; geomyoids), Carleton (1980; New World "cricetines"), Voss (1988; ichthyomyines), Carle- ton and Musser (1989; oryzomyines), and Voss and Carleton (1993; oryzomyines) for more de- tailed descriptions of this character in New World muroids. Each of these workers considered a com- plete stapedial system (state "0") to be primitive for the group they were discussing. In the primitive condition, the carotid artery splits into the internal carotid and the stapedial artery. The stapedial ar- tery passes into the auditory bulla, through the stapes, and into the cranium. After a split of the stapedial, the supraorbital branch passes along the internal surface of the squamosal and alisphenoid bones, leaving a groove as evidence of its passage, and eventually emerges through the sphenofrontal foramen. The "primitive" condition, with func- tional stapedial foramen, sphenofrontal foramen, and squamosal groove all present, is found in this survey in basal ichthyomyines (Voss, 1988), some thomasomyines, Wiedomys, some oryzomyines, akodontines, scapteromyines, Punomys, and vir- tually all phyllotines. Also common among sig- modontines in this survey are those conditions considered to be derived. These derived condi- tions are characterized by loss of the sphenofrontal foramen and loss of the supraorbital branch of the stapedial artery. Further loss of the infraorbital branch of the stapedial artery results in the re- duction of the stapedial foramen. These derived conditions are found in many oryzomyines, some thomasomyines, terminal ichthyomyines (accord- ing to Voss, 1988), Sigmodon, and among phyl- lotines in Reithrodon and Neotomys. Voss (1991) reported that Zygodontomys brevicauda shows well-defined discrete geographic variation for this trait, with one set of populations having a com- plete stapedial circulation and the other set lacking a complete stapedial circulation. It is interesting that this species shows geographic variation for two traits that are otherwise conserved at the ge- neric or even tribal level. 77P. Squamosal Fenestra— 2 states. = squamosal fenestra present where mastica- tory-buccinator nerve passes over the squa- mosal-alisphenoid groove 1 = squamosal fenestra absent Where the squamosal-alisphenoid groove cross- es the trough formed on the exterior of the alisphe- STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 39 noid by the masticatory -buccinator nerve, a fe- nestra often appears. Squamosal fenestrae were only observed in individuals with a squamosal— alisphenoid groove (i.e.. complete stapedial sys- tem), which is likely a structural necessity for the bone to be thin enough for the fenestra to occur. Under this argument, a fenestra cannot be present in animals with a derived stapedial system. This character was therefore coded as unknown in taxa with the derived stapedial system, which still al- lows the potential for incongruent ancestral state assignments under parsimony, but this should be unimportant to the analysis if it should happen. Polarity of this character is uncertain. Most phyl- lotines have the squamosal fenestra, although there is significant individual variation. Taxa with the complete supraorbital circulation that generally lack the fenestra include Galenomys. Euneomys. Irenomys. southern Andinomys. most Phylloi is. and Auliscomys pictiis. A reduced supraorbital circu- lation, where the stapedial foramen in the auditory bulla is present but constricted, and both the sphenofrontal foramen and squamosal-alisphe- noid groove are absent, is found among phyllo- tines only in Xeoiomys. Reithrodon is the only phyllotine without a stapedial artery. 23S ~SP. Alisphenoid Strut— 3 states. = absent or filamentous 1 = consistent dorsal process, but does not fully cross foramen ovale 2 = present and bony The absence of an alisphenoid strut is wide- spread among the phyllotines. but some individual variation is apparent. V'oss (1993) and Voss and Carleton (1993. Fig. 10) considered presence of the alisphenoid strut to be plesiomorphic for sig- modontines. Among phyllotines. a complete and consistent alisphenoid strut is found in Andalga- lomys. Eligmodontia, Graomys. Irenomys. and Reithrodon. In an intermediate condition, at the usual position of the strut, a process of the alisphe- noid extends into the foramen ovale from the dor- sal side. This condition is found in Euneomys and Chinchillula. Because there is no direct indication that a dorsal process is the intermediate state in transformations between absence and presence, the character states are treated as unordered. 24S. Hvoid— 3 states. = entoglossal process long and attenuate, ba- sihyal arched, thyrohyal long 1 = entoglossal process a small knob, basihyal arched. thvTohyal long 2 = entoglossal process absent, basihyal straight, thyrohyal short Transformation series and state descriptions follow Carleton (1980. Fig. 1 1), from which most of the data were gathered, but coding order was modified to allow linear ordering of the character states for the analysis. Carleton considered the in- termediate condition, with entoglossal process small, to be plesiomorphic for most muroid groups he surveyed. .All sigmodontines surveyed by Carle- ton ( 1 980) or myself lack an entoglossal process. Posteranial Skeleton 25S. .Articulation of First Rib— 2 states. = first rib articulates with first thoracic verte- bra only 1 = first rib articulates with transverse process of seventh cervical vertebra in addition to first thoracic vertebra .Articulation with the seventh cervical vertebra is recognized by the presence of a faceted articu- lation surface on the v ertebra's transverse process, in addition to apparent contact (Carleton. 1980, Fig. 15). Carleton (1980) considered dual articu- lation as derived within neotomine-peromyscines. The presence of both states among nonsigmodon- tines and the universal dual articulation among sigmodontines suggests that dual articulation may be a synapomorphy for the sigmodontines. 26S. Number of Thoracic and Lumbar Ver- tebrae— 3 states. 0=14 thoracic and 5 or 6 lumbar 1 = 13 thoracic and 6 lumbar 2=12 thoracic and 7 lumbar Thoracic v ertebrae w ere defined as having com- plete pairs of fully formed and articulating thoracic ribs. Supernumerary ribs are easily distinguished from complete ribs because they never articulate with the preceding v ertebra (as do complete ribs), are always shorter and thinner, may diverge at odd angles, and often exhibit enlarged and deformed heads. Supernumerary ribs that lack these condi- tions were considered to be associated with lumbar vertebrae. Carleton (1980) considered 13 thoracic and 6 lumbar vertebrae to be plesiomorphic for the New World muroids. The number of vertebral elements was surveyed across various taxa in ad- dition to those included in the phylogenetic anal- 40 FIELDIANA: ZOOLOGY ysis (Table 5, 179 species total). The Central American tylomyines, of uncertain affinities to the sigmodontines or neotomine-peromyscines, gen- erally have more thoracic vertebrae (13, 14, or 1 5) while maintaining the six lumbar vertebrae. Thir- teen thoracic and six lumbar vertebrae appear to be the widespread conditions among sigmodon- tines and are found in thomasomyines, ichthyo- myines, akodontines, phyllotines, and scaptero- myines. The apparent consistency of this character among generic groups suggests that it may be high- ly informative regarding oryzomyine relationships (Table 6). This trait appears more labile among the phyllotines than among the other sigmodon- tines (Steppan, 1993). A consistent pattern is observed among species that are polymorphic for the number of thoracic rib pairs and vertebral number. Of the 57 species found to be polymorphic for rib pairs, only 13 have minority variants with fewer than the modal number of thoracic ribs. In all other species, the minority variant has an additional pair of either complete ribs (3 1 species ) or incompletely formed supernumerary ribs (24 species) (the numbers of species just listed do not add up to 57 because some species have three or four conditions pres- ent). Only 6.3% of the 978 individuals examined differ from their species' modal count for true ribs. 79P. Number of Thoracic Rib Pairs— 2 states. 0=13 thoracic ribs 1 = 12 thoracic ribs The coding for the phyllotine analysis differs from the sigmodontine analysis in not including more than 1 3 ribs. The widespread and probably plesiomorphic condition among phyllotines is 1 3 ribs. Twelve ribs are found in Andalgalomys, Gra- omys, Reithrodon, and some Calomys. Some of these observations differ from pub- lished counts and deserve further discussion. Both Carleton (1980) and Olds (1988) reported that C. callosus has the plesiomorphic 1 3 ribs. Nineteen of the 20 skeletons of callosus examined in this study clearly had only 1 2 ribs and one had a thin, short thirteenth pair that did not articulate with the twelfth thoracic vertebra. Of the 1 1 skeletons examined by Carleton (1980), I could find only one individual that had more than 12 ribs (and the degree of articulation was unclear). Carleton (1980) also reported that both Graomys griseo- Jlavus and Sigmodon hispidus possess the plesio- morphic condition. Of the 13 skeletons of G. griseqflavus examined, 1 1 had 1 2 ribs, with no evidence that the thirteenth pair had been broken off; one appeared to have 1 2 ribs, but two addi- tional disarticulated ribs were found with this skeleton; and only one had a complete thirteenth pair. Of the two skeletons examined by Carleton ( 1 980), one was too damaged for an accurate count by me, and the other was not found. In G. do- morum, not previously reported, seven skeletons clearly had the derived condition, one had an extra thoracic pair (13T [thoracic] + 7L [lum- bar]), one was missing a lumbar vertebra ( 1 2T + 6L), and three had the plesiomorphic condition (13T + 6L). Ten of 13 skeletons of Sigmodon hispidus examined had the derived 12 thoracic and 7 lumbar rib pairs, as was observed by Voss (1992) in his revision of the South American spe- cies of Sigmodon. Three of the five skeletons ex- amined by Carleton (1980) were reexamined by me; one had 13 rib pairs, one had a supernu- merary pair, and one had a single supernumerary rib. This variation does not appear to be a prep- aration artifact. None of the specimens in species with moderate to large series and characterized as having 1 3 rib pairs were observed to have lost the last pair without leaving some evidence on the vertebrae. Additionally, the second lumbar vertebra can be recognized by an enlarged trans- verse process relative to those on the thoracics. This enlarged process would have obstructed an additional rib, if a rib had been present. 27P. Number of Caudal Vertebrae— 6 states. - > 40 1 = 36^0 2 = 30-35 3 = 24-29 4 = 20-23 5 = 11-19 Coding was derived from a histogram of all sur- veyed sigmodontine species (Table 5). Vertebral counts show limited variation in well-preserved specimens, typically with 80% of specimens within a range of two, with a few notable exceptions (Ho- lochilus brasiliensis, 25-34; Microryzomys minu- tus, 27-38; Oecomys concolor, 32-38; Oligoryzo- mys microtis, 31-38; Macrotarsomys bastardi, 30-40). This variation within species may reflect currently unrecognized taxonomic diversity or misidentification of specimens. Carleton (1980) was unable to reliably estimate polarity for this character. Nearly the entire range of variation is found among the outgroups, from state "1" in Nyctomys to state "5" in some "cricetids," but the extremes are likely to be derived in both sigmo- dontines and outgroups. STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 41 Table 5. Vertebral counts among Neotropical sigmodontines and selected muroids. Taxon a Thoracic^ Lumbar CaudaL Tribe Akodontini Akodon yAbrothrix) longipilis A. (Abrothrix) sanborni A. (Akodon) aerosus A. albiventer A. azarae A. boliviensis A. cursor A. mollis A. neocenus A. olivaceus A. puer A. puer lutescens A. subfuscus A. torques A. urichi A. xanthorhinus A. (Deltamys) kempi A. (Microxus) bogotensis A. (A/.) mimus A. (Thaptomys) nigrita Bolomys amoenus B. lasiurus B. obscurus B. temchuki Chelemys macronyx Chroeomys andinus C. jelskii Geoxus valdivianus Notiomys edwardsii Oxymycterus delator O. inca O. platensis O. rufus Thalpomys lasiotis 10 13 6 26-29 (28) 1 13 5 7 13 6 24-27 8 13 6 27-29 7 13 6 23-25 2 13 6 26 1 13 + 1 6 > 24 5 13 6 24-26 1 13 + 1 6 1 13 7 24-25 11 13 6 27-28 4 13 6 28 3 13 6 24-25 15 13 6 25-27 2 12 7 25 4 13 6 24-26 1 14 6 25 2 13 6 21-22 7 13 6 24-27 8 13 6 28-30 1 14 5 30-31 5 13 6 24-27 11 13 6 22-23 (22) 1 13 + 1 2 13 6 29-30 1 12 7 25 1 14 5 25-26 10 13 6 27-30 2 12 + 1 7 1 12 7 30 1 12 6 > 24 6 13 6 23-24 8 13 6 23-26 (26) 1 13 + 1 7 26 4 12 7 23-25 1 ? 6 > 19 1 13 6 1 13 6 27 9 13 6 20-22 3 13 6 22-23 12 13 6 23-26 (25) 9 13 6 21-23(22) 1 13 6 18 6 13 6 27-29 (28) 9 13 6 25-26 1 13 + 1 6 25-26 1 14 6 25 4 13 6 26-27 8 13 6 26 1 13 7 25 1 13 6 19 7 14 6 33-34 (33) 3 14 5 30-33 1 13 6 1 13 6 » 25 1 13 6 30-33 Tribe Ichthyomyini Anotomys leander Chibchanomys trichotis 1 Ichthyomys hydrobates I. pittieri f 42 FIELDIANA: ZOOLOGY Table 5. Continued. Taxon a N" Thoracic Lumbar'' Caudal' /. tweedii Neusticomys monticolus N. venezuelae f Rheomys mexicanus f R. raptor R. thomasi R. underwoodi 4 13 6 32-34 7 13 6 29-30 2 14 5 30-33 8 13 6 > 33 1 14 6 4 13 6 32-33 12 13 6 > 30 1 14 5 33 V 14 6 2 13 6 30-33 8 12 7 25-34 (25-26, 29-30, 34) 7 12 7 29-32 1 11 7 29 4 12 7 33-35 6 12 7 29-32 2 11 7 29 2 12 7 36 9 12 7 28-29 1 13 6 28 2 12 7 37 1 12 6 2 12 7 37-38 1 12 ? 27 1 12 6 1 13 6 5 12 7 29-31 10 12 7 32-35 1 12 8 1 13 6 > 33 3 12 7 32-33 1 13 6 33-34 8 12 7 31-32 1 13 6 > 25 2 12 7 » 25 1 13 6 27 11 12 7 34-37 (36) 3 12 + 1 7 35 1 12 7 32-33 2 12 7 36,38 1 12 7 1 12 7 38 4 12 7 37-39 1 12 + 1 7 37 2 12 7 38-39 1 13 7 3 12 7 37-38 1 12 + 1 7 37 1 12 7 > 34 1 12 + 1 7 1 13 6 36 7 12 7 32-35 (34) 2 12 + 1 7 35 2 12 7 35-36 1 12 + 1 7 35 1 13 7 2 12 7 35-36 1 13 6 Tribe Oryzomyini Holochilus brasiliensis brasiliensis g H. brasiliensis vulpinus H. chacarius Lundomys molitor Melanomys caliginosus Microryzomys altissimus M. minutus Neacomys guianae N. spinosus N. tenuipes Nectomys squamipes Nesoryzomys indefessus indefessus N. indefessus narboroughi Oecomys bicolor O. concolor O. mamorae O. paricola O. roberti O. superans O. trinitatis Oligoryzomys andinus O. chacoensis O. delticola O. destructor STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 43 Table 5. Continued. Taxon" N* Thoracic^ Lumbar" Caudal' O. eliurus O. jlavescens O. fulvescens O. longicaudatus O. magellanicus O. microtis O. microtis fornesi O. nigripes Oryzomys albigularis O. alfaroi O. bolivaris O. buccinatus O. capito O. chapmani O. couesi O. intermedins O. keaysi O. melanotis O. nitidus O. palustris O. polius O. ratticeps O. subflavus O. talamancae Pseudoryzomys simplex Sigmodontomys alfari Zygodontomys brevicauda 1 12 7 37 5 12 7 34 4 12 7 32-33 1 12 + 1 7 32-33 1 13 7 32 6 12 7 33-35 1 13 6 35 2 12 7 « 31 3 12 7 31-33 1 12 8 1 13 7 32 1 11 7 3 12 7 34-38 2 13 6 31-32 6 12 7 31-36 1 12 + 1 7 > 28 1 13 7 35 4 12 7 37 2 12 + 1 7 > 34 4 12 7 36-37 1 12 7 3 12 7 38-40 10 12 7 27-28 2 13 6 > 28 3 12 7 32-33 3 12 7 > 30, 33 6 12 7 29-31 5 12 7 36-37 4 12 7 30-32 1 12 7 31 8 12 7 32-33 1 12 + 1 7 2 12 7 35-36 1 12 8 35 4 12 7 37-39 3 12 7 35-36 6 12 7 29 1 12 + 1 7 > 28 1 12 7 29-30 1 12 8 4 12 7 33-36 5 12* 7 > 26, 34 1 13 6 * 38 1 13 6 > 36 1 12 7 > 33 1 13 6 30 1 12 + 1 7 > 27 2 13 6 30 5 12 7 * 38 2 13 6 37 1 13 6 35 4 13 6 35-37 1 13 6 40 2 12 7 38^1 1 12 + 1 7 1 12 7 1 12 7 > 38 "Thomasomyine group' Aepeomys lugens Chilomys instans Delomys dorsatis D. sublineatus Rhipidomys couesi R. fulviventer R. latimanus R. macconnelli R. mastacalis R. nitela R. scandens 44 FIELDIANA: ZOOLOGY Table 5. Continued. Taxon" V Thoracic^ Lumbar' CaudaF R. venezuelae R. venustus Thomasomys aureus T. baeops T. cinereus T. daphne T. gracilis T. hylophilus T. oreas T. paramorum T. pyrrhonoius T. rhoadsi Wiedomys pyrrorhinos 12 12 13 13 13 13 13 14 13 13 13 13 13 13 13 + 1 13 12 39^12 39-40 41-43 41 37^1 42 41 38 41 38 35-39 (38) > 38 39 39 Tribe Phyllotini Andalgalomys pearsoni Andinomys edax Auliscomys boliviensis A. pictus A. sublimis Calomys bolivae C. callosus C. hummelincki C. laucha C. lepidus C. musculinus C. sorellus C. tener C. venustus Chinchillula sahamae Eligmodontia morgani E. puerulus Euneomys chinchilloides Galenomys garleppi Graomys domorum G. griseojlavus 6 4 1 4 4 19 1 2 1 5 2 1 9 1 4 7 1 2 1 1 11 2 1 1 1 1 1 6 1 10 6 6 3 1 1 12 1 12 13 13 13 14 13 12 12 12 + 1 12 13 12 12 13 13 12 + 1 13 13 13 12 ? + 1 14 13 13 14 12 12 13 13 13 13 13 13 12 13 13 12 12 13 31 28-30 (30) 25-27 22-26 27 24-25 * 25 22-25 (23-24) 25 21-23 21-22 21-23 20-22 27-28 24-26 29 27-28 30-31 29 24 22 25 > 21 25-26 26 22-24 (22) 17-19 31-32, 35 32-34 32-35 35 STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 45 Table 5. Continued. Taxon" V : Thoracic Lumbar" Caudal' Irenomys tarsalis Loxodontomys micropus Phyllotis amicus P. andium P. caprinus P. darwini P. gerbillus P. haggardi P. osilae P. wolffsohni P. xanthopygus rupestris P. xanthopygus xanthopygus Reithrodon auritus 8 13 6 34-39 1 13 + 1 6 6 13 6 28-29 1 13 7 > 26 1 13 6 35-36 3 13 6 34 2 13 6 33-34 10 13 6 28-35 (32) 1 13 6 27 1 13 + 1 7 30 3 13 6 > 27 19 13 6 31-34(32,33) 6 13 6 36 [n = 1] 6 13 6 32-33 1 13 + 1 6 34 29 13 6 29-33(31) 1 12 7 9 12 7 24 1 13 6 25-26 Tribe Scapteromyini Scapteromys tumidus 13 12 28-30 (29) > 26 Tribe Sigmodontini Sigmodon alleni S. fulviventer S. hispidus S. leucotis S. ochrognathus 12 12 12 12 12 + 13 13 12 13 12 25 23-25 23 24 23 25 > 19 25-27 Tylomyines Nyctomys sumichrasti Ototylomys phyllotis phyllotis O. phyllotis fumeus Tylomys fulviventer T. mirae T. nudicaudus T. panamensis T. watsoni 13 13 12 15 14 14 14 + 1 14 14 13 15 14 14 36-37 37 30-33 33-36 35^10 33 « 33 35-36 32 35-36 Neotomine-Peromyscines Baiomys musculus Ochrotomys nut t alii Scotinomys teguina 13 13 13 > 23 26 26 Nesomyines Brachytarsomys albicauda Brachyuromys ramirohitra 13 13 35 24 46 FIELDIANA: ZOOLOGY Table 5. Continued. Taxon a N* Thoracic^ Lumbar CaudaP Eliurus myoxinux Gymnuromys roberti Macrotarsomys bastardi Nesomys audeberti N. rufus 1 13 7 27-30 2 13 7 > 27 4 13 7 33, 37, 39, 40 1 12 + 1 8 w 30 2 13 7 * 30 4 13 7 29-31 5 13 6 28-30 1 13 6 16 4 13 6 17 1 13 + 1 6 17 4 13 6 16-17 2 13 6 12 1 13 6 24 5 13 6 11 1 13 7 9 1 13 6 22 Old World "cricetids" Calomyscus baluchi Cricetulus barabensis C. longicaudatus Cricetus cricetus Mesocricetus auratus Mystromys albicaudatus Phodopus sungorus Tscherskia triton " Specific and generic taxonomy follows Musser and Carleton (1993). * Number of skeletons examined for each vertebral count category. ' Number of thoracic ribs as defined by pairs of fully formed thoracic ribs. Number after plus sign indicates the number of pairs of supernumerary ribs. d Number of lumbar vertebrae, including vertebrae with supernumerary ribs. * Numbers in parentheses indicate modal counts for species with sufficiently large sample sizes. 'Data from Voss (1988, Table 10). 8 Associating Holochilus with the oryzomyines rather than with Sigmodon has been suggested based on several organ systems and presented by Voss and Carleton (1993). * One individual has a supernumerary rib that arises from the seventh cervical vertebra. Table 6. Distribution of selected characters among oryzomyine and thomasomyine genera. Zygomatic Taxon Gallbladder 1 Ribs Mammae Hemal arch notch Thomasomys Present 13 6 Present at low frequency Shallow Chilomys Present 13 6 Absent Shallow Delomys Present 13 6-8 Absent Deep Nesoryzomys Absent 13 ? Absent Deep Neacomys Absent 12 6 Square Shallow Oecomys Absent 12 8 Square Shallow Microryzomys Absent 12 8 ?Spinous? Shallow Melanomys Absent 12 8 Spinous Medium Nectomys Absent 12 8 Spinous Deep Oligoryzomys Absent 12 8 ?Spinous? Deep Oryzomys Absent 12 8 Spinous Deep Pseudoryzomys Absent 12 8 Spinous Deep Zygodontomys Absent 12 8 Spinous Deep Holochilus Absent 12 10 Spinous Deep "Voss (1991). • Gyldenstolpe (1932), Hershkovitz (1955), and Voss (1993). STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 47 Fig. 17. Ventral view of caudal vertebrae 1-5 in Nectomys squamipes (fmnh 14163), indicating the hemal arches (ha) and hemal processes (hep). 80P. Number of Caudal Vertebrae— 3 states. = < 25 1 = 25-30 2 = > 30 Tail length— Not analyzed. Tail length is highly correlated with number of caudal vertebrae and provides the more common definition of this gen- eral trait. Olds and Anderson (1989) described tail length as variable within Phyllotini, but they none- theless chose to include it in their data matrix. While indeed being quite variable within the phyl- lotines (ranging from 0.33 to 1.4 times head and body length), tail length seems to be more con- served and therefore informative outside the phyl- lotines. Most sigmodontines (oryzomyines, tho- masomyines, ichthyomyines) have moderate to long tails (> 0.85 head and body length). Olds and Anderson (1989) agreed with Hershkovitz (1962, p. 54) that short and long tails are derived from moderate-length tails. It is unclear in both works whether this polarity only refers to sigmodontines in general or is also a statement about the ancestral condition in phyllotines. 8 IP. Neural Spine of Second Thoracic Ver- tebra— 2 states. = longest spine present on T2 (at least twice as long as nearby spines) 1 = short on T2, instead longest on T3 All sigmodontines except the ichthyomyines have a greatly enlarged neural spine on the second vertebra that acts as the site of attachment for the nuchal ligament (Voss, 1988). Voss reported that in ichthyomyines the spine of the third thoracic is both enlarged and the attachment site for the lig- ament. An enlarged spine on the second thoracic vertebra is plesiomorphic and widespread for the phyllotines just as in the sigmodontines. However, Euneomys also has an enlarged spine on the third thoracic. The only other occurrence of this derived condition among phyllotines is in Reithrodon. In 16 skeletons of Reithrodon auritus pachycephalia, one had a longer spine on the third thoracic ver- tebra and five had second and third spines of ap- proximately equal length. 82P. Height of Neural Spine of Second Cervi- cal Vertebra— 3 states. = not significantly enlarged 1 = enlarged, distinct knob 2 = very enlarged into distinct keel, "plow"- shaped, may overlap C3 The widespread condition among phyllotines is for the neural spine on the second cervical vertebra to be enlarged into a distinct knob, usually wider than long. In the likely derived condition, the knob is further enlarged into a distinct plow-shaped keel that may overlap the third cervical vertebra. This condition is found in Andinomys and Neotomys. The least developed condition was found by this survey only in Akodon. 8 3 P. Length of Neural Spine of Second Cervi- cal Vertebra— 2 states. = does not overlap C3 1 = does overlap C3, excluding situation where height is very enlarged Among phyllotines without a greatly enlarged neural spine on the second cervical vertebra, the widespread condition is for that spine to not over- lap the third cervical vertebra. Alternatively the knob is angled posteriorly and overlaps the third cervical. This condition is found in Andalgalomys, Euneomys, and some Graomys griseoflavus. 28S. Hemal Arch— 3 states (Fig. 17). = absent 1 = present, with simple posterior border 2 = present, with spinous posterior border In the majority of sigmodontines, the median coccygeal artery, which passes along the ventral 48 FIELDIANA: ZOOLOGY side of the tail, is bounded by hemal processes at the vertebral junctions, usually starting between the second and third, becoming most pronounced between the fourth and fifth, and then diminishing along the next five to ten vertebrae. The hemal arch is a complete bony ring enclosing the artery and is typically located at the joint between the second and third caudal vertebrae (Fig. 1 7). Hemal arches are commonly found among other mam- malian orders. In species with additional arches between the first and second and/or the third and fourth caudal vertebrae, the arch between the sec- ond and third is usually the most complex or most developed. Among surveyed pentalophodont gen- era with 1 2 thoracic vertebrae (Table 6), all appear to possess a "ring"-shaped hemal arch (except Wiedomys). The posterior edge of the arch is extended into a distinct spinous process in Nec- tomys, Pseudoryzomys, Zygodontomys, most Ory- zomys, and possibly Microryzomys. An unmodi- fied hemal arch is found in Oecomys, Neacomys, Oryzomys albigularis, O. capito, and possibly O. xanthaeolus, as well as sporadically among some thomasomyines, but sample sizes are small and arches are often damaged. I observed a hemal arch in only two tetralophodont genera, Andinomys and Sigmodon (in both cases, the arch lacked a spinous process). 84P. Position of Deltoid Tuberosity— 2 states. = < 59%, measured from condyle of humerus to notch of deltoid tuberosity relative to total length 1 = > 59% The position of the deltoid tuberosity on the humerus is measured as the percentage of total humerus length from the condyle to the notch of the tuberosity. The widespread condition for phyl- lotines is for the tuberosity to be less than 59% of the total length from the condyle. 29S. Entepicondylar Foramen— 2 states. = present 1 = absent The presence of an entepicondylar foramen, lo- cated above the medial epicondyle of the humerus and next to the supertrochlear foramen (Carleton, 1 980, Fig. 1 3), was considered by Carleton ( 1 980) to be primitive for neotomine-peromyscines. It is present in tylomyines (sensu Carleton, 1 980), most neotomine-peromyscines and Old World "crice- tids," but absent in all sigmodontines examined. 30S. Supertrochlear Foramen— 2 states. = absent 1 = present Polarity of this character is difficult to deter- mine, but most outgroup taxa lack it. All sigmo- dontines have a supertrochlear foramen except Rhipidomys latimanus. Carleton (1980) did not report on this character. 3 1 S. Proximal Extent of Fifth Metatarsal— 2 states. = peroneal process of fifth metatarsal equal with or proximal to the distal edge of calcaneum (articular surface with the cuboid) 1 = fifth metatarsal not proximal to cuboid/cal- caneum articulation Taxonomic coverage is limited, but a "long" peroneal process (state "0") was found only among the outgroups. 32S. Trochlear Process of Calcaneum — 2 states. = level with posterior articular facet, process broad and shelf-like 1 = gap between proximal edge of process and posterior articular facet, process shorter and less shelf-like Coding for this character largely follows Carle- ton (1980), except that his state "2" was not ob- served among species I surveyed and is not in- cluded. Carleton (1980) considered the most proximal position of the process (state "0") to be plesiomorphic for the neotomine-peromyscines, but that is unlikely to be true also for the sigmo- dontines, among which I did not observe state "0." Both character states were found among the out- groups. External Morphology 85P. Ventral Surface of Claws (Manus)— 3 states. = open basally 1 = closed basally, without strongly developed keel 2 = fused, forming distinct keel The widespread condition among phyllotines is for claws to be closed basally, without developing a distinct keel. In Eligmodontia, Chinchillula, Au- liscomys pictus, and A. sublimis the claw is strongly fused basally, forming a distinct keel. Phyllotis wolffsohni, alone among phyllotines, has a claw that is not closed basally. STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 49 86P. Length of Dl Relative to D5 (Pes)— 2 states. = Dl distinctly shorter than D5 1 = D 1 and D5 subequal in length, not extending past first interphalangeal joint of D2-4 The widespread condition among phyllotines is for digit 1 to be distinctly shorter than digit 5. Reduction in the length of D5 so that it is subequal in length with Dl and does not extend past the bases of D2— 4 is present in Reithrodon and Elig- modontia. Outside the phyllotines, such short out- er digits are also seen in genera with varying lo- comotor modes: Oxymycterus, Sigmodon hispidus, Kunsia, Bolomys, Akodon (Thaptomys), Holochi- lus, and Scapteromys. 87P. Position of Hypothenar Pad— 2 states. = hypothenar extending distally beyond prox- imal base of the first interdigital pad 1 = intermediate to first interdigital and thenar pads The widespread condition among phyllotines is for the hypothenar to extend distally beyond the base of the first interdigital pad. This is in contrast to the widespread condition among surveyed out- groups, where the hypothenar is intermediate be- tween the first interdigital and thenar pads without significantly overlapping the position of either. The hypothenar is absent in the highly derived hindfeet of Eligmodontia. 33S 8 8 P. Furring of Soles of Feet (Pes)— 3 states. = sparse hair only on heels 1 = heels furred, distal pads naked 2 = heel and distal pads furred Olds and Anderson (1989) listed this character among the possible phyllotine synapomorphies and included it in the diagnosis but did not include it in their data matrix (1989, Table 1). Their dis- cussion implied that it is a widespread condition among sigmodontines while among phyllotines it is characterized by species-specific adaptations to local environments. Furred heels are found in tho- masomyines, akodontines, and some phyllotines. Furring of the soles of the hindfeet in phyllotines varies from sparse lateral fur that extends toward the sole, to more extensive furring around and onto the sole of the heel, to furring among the distal pads. The third condition is easily distin- guished from the first two, which have no hair at all in the broad distal portion of the sole. 34S. Ear (Pinna) Size— 4 states. = < 0.068 combined head and body length 1 = 0.069-0. 108 combined head and body length 2 = 0.1 08-0. 150 combined head and body length 3 = > 0. 1 50 combined head and body length Character state values were determined using the segment-coding technique on log-transformed ratios as described in the Materials and Methods section. There are minor differences between Olds and Anderson (1989) and this study in the size estimation and coding of several species. These differences may be a product of sampling. Four of the five species with the relatively largest ears sam- pled belong to phyllotines. 89P. Countershading of Tail— 3 states. = distinctly bicolored 1 = indistinctly bicolored 2 = monocolored Both distinctly and indistinctly bicolored tails are common among phyllotines and sigmodon- tines, making polarity equivocal. Indistinctly bi- colored tails have a weak but noticeable contrast between the darker dorsum and lighter underside. Distinctly bicolored tails have a sharp contrast between the dorsal and ventral sides. Monocol- ored tails are found scattered among the phyllo- tines. 90P. Furring of Tail Dorsum— 3 states. = sparsely furred, scales evident 1 = furred, scales visible but indistinct 2 = densely furred, scales scarcely visible Moderately furred tail is the most common character state among phyllotines. 9 IP. Body Pelage Pattern— 3 states. = distinctly countershaded 1 = indistinctly or not countershaded The widespread condition among phyllotines is for the dorsum and sides of the body to be a con- trasting color and tone from the undersides. No phyllotine is considered to be monocolored, but Euneomys and Neotomys are indistinctly bicol- ored. 92P. Pectoral Streaks— 2 states. absent present Only a minority of phyllotine species possess pectoral streaks, and those few are concentrated 50 FIELDIANA: ZOOLOGY in the genus Phyllotis. A pectoral streak is usually an ocher coloration to the fur along the midline in the pectoral region, approximately circular to longitudinal in shape, often presenting a subtle contrast to the predominantly neutral color of the undersides and usually limited to a streak rather than spreading laterally toward the shoulders. Pec- toral streaks are found in Neotomys, Loxodonto- mys, P. osilae, P. magister, P. definitus, P. wolff- sohni, and at small to moderate frequencies in some populations of P. xanthopygus. 35S. Mammae Number— 4 states. = 4 1 = 6 2 = 8 3 = 10 or more Four pairs of pectoral, postaxial, abdominal, and inguinal mammae constitute the widespread con- dition among the Sigmodontinae. Six mammae (postaxial, abdominal, and inguinal) are found in the thomasomyines (e.g., Thomasomys, some De- lomys, Rhipidomys), all ichthyomyines, some ory- zomyines (just Neacomys), Wiedomys, and the "problematic" Rhagomys (Reig, 1980). Voss (1993) considered six mammae to be plesio- morphic for the sigmodontines. Mammae number may be intraspecifically variable in Delomys dor- salis (6-8; Voss, 1993), but sharp geographic seg- regation of the mammary counts suggests that two species may be present. More than eight mammae are found only in some Calomys, Sigmodon, and Holochilus. Thus, eight mammae is likely plesio- morphic for the phyllotines, but the presence of six versus eight mammae may be highly infor- mative for pentalophodont sigmodontines (Table 6). Characters of the Phallus and Soft Anatomy 36S. Bacular Complexity— 2 states. = lateral bacular mounds present 1 = lateral bacular mounds absent The complex penis with lateral bacular mounds present has conventionally been considered prim- itive for most muroids (Hooper & Musser, 1 964; Hershkovitz, 1966b). Carleton (1980) hypothe- sized that the simple penis was primitive for the neotomine-peromyscines. I coded taxa with high- ly reduced and peculiar lateral mounds (Nyctomys, Scapteromys) as unknown given this simplified coding scheme. Spotorno (1992) considered re- duced or absent lateral mounds to be derived for New World murids and linked with a suite of traits partially controlled by hormonal levels. 93P. Distal/Proximal Bacular Length— 3 states (Fig. 18). = < 0.63 1 = 0.63-0.77 2 = > 77 The landmarks chosen to define this character are from the distal tip of the medial digit of the distal baculum to the distal tip of the proximal and from the tip of the proximal to the line con- necting the widest points of the base. The common condition for phyllotines is for an intermediate- sized distal baculum, 63-77% the length of the proximal baculum. A large distal baculum, ranging from 79 to 105% the proximal length, character- izes most members of the P. xanthopygus species group (P. xanthopygus, P. darwini, P. magister, and P. caprinus; Steppan, 1993). No sigmodon- tines outside Phyllotis have such relatively large distal bacula (Hooper, 1962; Hooper & Musser, 1964; Hershkovitz, 1966b; Spotorno, 1986; this study). 94P. Length of Lateral Mounds Relative to Medial Mound— 2 states. = > % 1 = < % The widespread and likely plesiomorphic con- dition among phyllotines is for the lateral mounds to be greater than % the length of the medial bacu- lar mound. Auliscomys sublimis and A. pictus share the derived condition where the lateral mounds are less than % the medial length. Andinomys is unusual in having lateral mounds that are longer than the medial (Spotorno, 1986). 9 5 P. Hooks on Lateral Mounds— 2 states (Fig. 18). = absent 1 = present, pointing basally The widespread condition among sigmodon- tines and phyllotines, and thus likely the plesio- morphic condition among phyllotines, is for the lateral mounds of the distal baculum to be simple and unmodified. The presence of basally directed hooks projecting from the tips of the lateral mounds is unique to the Phyllotis xanthopygus species- group (Fig. 18). The condition in P. definitus is unclear; while Spotorno (1986, Fig. 5.9) indicates STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 51 Fig. 18. Ventral and lateral views of bacular apparatus in Phyllotis magister (fmnh 107469). dn, dorsal knob of lateral mounds; ldb, length of distal baculum; lh, lateral hooks; lpb; length of proximal baculum. the presence of small hooks, species similarly drawn in that publication do not possess hooks among FMNH specimens examined by me. Preparation differences are probably the cause of the differing observations. 9 6 P. Knob on Dorsal Surface of Lateral Mounds— 2 states (Fig. 18). = absent 1 = present Small knobs project from the middorsal surface of the lateral mounds in the species Phyllotis xan- thopygus, P. caprinus, and P. magister (Fig. 1 8). Suitably prepared phalli of P. darwini were not available for examination. All other examined species lacked the dorsal knobs. 37S. Preputial Glands— 3 states. = absent 1 = one pair present 2 = two pairs present Data and character coding are adapted from Voss and Linzey (1981). Male accessory glands show little phylogenetically informative variation among the sigmodontines (Voss & Linzey, 1981). The ex- ceptions are ventral prostrates, which vary only among akodontines, and the number of preputial glands. At least one species in each major generic- group possesses a single pair, with the exception of the oxymycterines and Sigmodon. A single pair or no preputials are both widespread among other muroids (Carleton, 1980), but absence of prepu- tials is found only in several oryzomyines and tho- masomyines (4 of 1 7 species surveyed). Two pairs were not reported by Carleton (1980) or Voss and Linzey (1981) outside the South American Sig- 52 FIELDIANA: ZOOLOGY modontinae. The plesiomorphic state for sigmo- dontines therefore appears to be one pair. Two pairs of preputials occur in Chroeomys jelskii (my observations suggest small third or even fourth pairs), oxymycterines (sometimes raised to tribal status, otherwise treated as a subgroup within the akodontines), Sigmodon, and most phyllotines. 97P. Preputial Glands— 3 states. = single large lateral pair 1 = single large lateral pair with very small ( < 1 mm) medial pair 2 = single large lateral pair with medium length {2-A mm) medial pair Two sources of data on preputial glands were available for this study: Voss and Linzey's (1981) study on male accessory glands in New World mu- roids and my observations of partially cleared and stained phalli. The coding was adjusted to reflect the range of variation observed in phyllotines as compared to sigmodontines. Voss and Linzey (198 1) found one pair (» 10 mm) in Calomys (C callosus and C. laucha), while the rest of the sur- veyed phyllotines (Andalgalomys pearsoni, Elig- modontia typus, Graomys griseqflavus, P. darwini, and P. osilae) had a second smaller ventral pair (2.5-3.5 mm). The material examined by Voss and Linzey (1981) consisted of phalli dissected from fluid-preserved carcasses stored in 70% alcohol. I examined phalli that had been partially cleared and stored in glycerin. With microscopic exami- nation of dissected and backlit phalli, I found that greater detail could be observed than with un- cleared alcohol-preserved specimens. My obser- vations of species of Akodon, Chroeomys, Calo- mys, Phyllotis, Auliscomys, Irenomys, and Neotomys all support the observations of Voss and Linzey (1981). However, C. sorellus was found to have a very small ventral pair of glands in exactly the same position and with the same texture and shape as the ventral pair in the other phyllotines. This ventral pair is so small, 0.5-0.8 mm, that it is possible that Voss and Linzey would not have recognized it using their methods had they ex- amined C. sorellus. Because I did not have access to appropriately cleared phalli of C. callosus and C. laucha to confirm the absence of such a small ventral pair of glands, these two species were cod- ed as unknown ("?"). All nine specimens of P. xanthopygus chilensis examined by me have an additional third pair, 1 mm long and situated be- tween the lateral and medial pairs. 38S 98P. Gallbladder— 2 states. = absent 1 = present Carleton ( 1 980) and Voss (1993) considered the presence of a gallbladder to be plesiomorphic among New World "cricetids." Voss (1991) ex- amined 93 species of sigmodontine rodents for the presence of a gallbladder. This character shows little variation within tribes or major generic groups. The only exceptions seem to be charac- teristic of unrelated scattered genera. A gallbladder is present in all surveyed akodontines except Len- oxus and Akodon cursor, all ichthyomyines except Ichthyomys, all thomasomyines except Rhipido- mys, all phyllotines, the scapteromyines, and Sig- modon (Punomys was not examined). It is absent in all oryzomyines, including Pseudoryzomys, Zygodontomys, and Holochilus. All 16 surveyed phyllotines have a gallbladder (Voss, 1991). 39S. Gastric Epithelium 1—4 states. = hemiglandular 1 = intermediate, reduction in glandular zone around antrum 2 = discoglandular 3 = pouched 40S. Gastric Epithelium II— 2 states. = hemiglandular 1 = intermediate, reduction in glandular zone along greater curvature Data and coding are slightly modified from Carleton (1973). Character 40S is treated as a sep- arate character to distinguish the intermediate condition found in ichthyomyines from that found in Thomasomys and Scapteromys. The large ma- jority of sigmodontines possess the hemiglandular condition. Phylogenetic Relationships within Sigmodontinae Results When the analysis includes the dummy variable to favor sigmodontine monophyly, 28 equally most-parsimonious trees result, the strict consen- sus of which is presented in Figure 19. Each of the most-parsimonious trees (including outgroups) is 287 steps long with a CI of 0.26 and RI (Farris, 1989) of 0.61. When only the sigmodontines are considered, the respective values are 195 steps, CI STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 53 3 § IS 5 5 8 §"9 c og <2-2 It IS 54 FIELDIANA: ZOOLOGY Table 7. Consistency and retention indexes for sigmodontine characters. Number Character name CI* RI" 1 . Mesoloph(-id) 2. Length M3 3. Shape M2 4. Posterior extent of incisive foramina 5. Dorso ventral position of anterior root of zygomata 6. Posterior margin of zygomatic plate 7. Masseteric tubercle 8. Zygomatic notch 9. Posterior extension of nasals 10. Posterior extension of premaxillaries 1 1 . Supraorbital edge 1 2. Shape of frontoparietal suture 1 3. Ratio of interparietal/parietal length 14. Parietal/occipital contact 15. Tegmen tympani 16. Squamosal fold 1 7. Subsquamosal foramen 18. Relative width of mesopterygoid fossa 1 9. Shape of mesopterygoid fossa 20. Sphenopalatine vacuities 2 1 . Position of anterior border of mesopterygoid fossa 22. Carotid circulation 23. Alisphenoid strut 24. Hyoid 25. Articulation of first rib 26. Number of thoracic and lumbar vertebrae 27. Number of caudal vertebrae 28. Hemal arch 29. Entepicondylar foramen 30. Supertrochlear foramen 3 1 . Proximal extent of fifth metatarsal 32. Trochlear process of calcaneum 33. Furring of soles of feet (pes) 34. Ear (pinna) size 35. Mammae number 36. Bacular complexity 37. Preputial glands 38. Gallbladder 39. Gastric epithelium I 40. Gastric epithelium II 0.333 0.733 0.333 0.429 0.167 0.286 0.429 0.636 0.400 0.625 0.333 0.556 1.000 1.000 0.667 0.857 0.143 0.500 0.333 0.636 0.300 0.462 0.400 0.500 0.333 0.556 [1.000]* [1.000] 0.500 0.875 [0.500] [0.667] 0.333 0.500 0.250 0.500 0.286 0.545 0.600 0.875 0.231 0.265 0.200 0.429 0.200 0.636 [0.667] [0.833] [0.500] [0.800] 0.500 0.818 0.444 0.500 0.667 0.875 [0.500] [0.833] [0.333] [0.750] [1.000] [1.000] [0.500] [0.800] 0.333 0.636 0.300 0.462 0.400 0.700 [0.333] [0.500] 0.400 0.500 0.333 0.778 0.750 0.667 1.000 1.000 " Character indexes calculated over the sigmodontine portion only of the strict consensus tree in Figure 19. * Indexes in brackets (e.g., [0.500]) were calculated over the entire tree, including outgroups, because the character was invariant or uninformative within the sigmodontines. = 0.33, and RI = 0.63. The CIs are at or slightly below the values expected for the number of taxa, based on a survey of other published studies (Ar- chie, 1989; Sanderson & Donoghue, 1989), and well within the range of surveyed studies. All anal- yses designated the Old World "cricetids" as the outgroups. Table 7 lists CIs and RIs for each char- acter. The tree in Figure 1 9 was produced by including a dummy variable: all outgroups coded as "0," all sigmodontines coded as " 1 ." The dummy variable had to be weighted four times the standard weight before a monophyletic Sigmodontinae was among the most-parsimonious trees. When no dummy variable was included, the trees in Figure 20 re- sulted (strict consensus of 1 8 trees, each 282 steps long). The deviations from monophyly in Figure 20 are the inclusion of the South African Mystro- mys within the phyllotines as the sister taxon to Reithrodon, the placement of the neotomine-per- omyscine Scotinomys at a basal position within the sigmodontines, and Wiedomys dropping down into the neotomine-peromyscines. Only one step is needed to remove Scotinomys from the sig- STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 55 • Oryzomys capito , Oryzomys palustris tE ^ Nectomys squamipes Zygodontomys brevicauda Holochilus brasiliensis Pseudoryzomys simplex Oligoryzomys fulvescens Neacomys spinosus Chilomys instans Anotomys leander Ichthyomys hydrobates Neusticomys monticolus w^Akodon boliviensis 1— Akodon albiventer Kunsia tomentosus Sigmodon hispidus Calomys callosus Graomys griseoflavus Reithrodon auritus Mystromys albicaudatus Phyllotis darwini Neotomys ebriosus Punomys lem minus Scapteromys tumidus Oxymycterus hispidus Thomasomys rhoadsi Rhipidomys latimanus Thomasomys aureus Thomasomys baeops Scotinomvs teauina Ochrotomvs nuttalli Peromyscus leucoous Wiedomys pyrrhorhinos Calomyscus baluchi Nyctomvs sumichrasti Tylomys nudicaudus Neotoma floridana Cricetulus migrator ius Mesocricetus auratus Phodopus sunaorus 56 FIELDIANA: ZOOLOGY modontines and place Wiedomys among them, but all four steps are needed to remove Mystromys. The seemingly unlikely placement of Mystromys, both on conventional systematic and biogeograph- ic grounds, leads me to prefer the weighted tree with the monophyletic Sigmodontinae. Characters that unequivocally support a monophyletic Sig- modontinae given the outgroup topology in Figure 1 9 {Scotinomys as the sister-group to Sigmodon- tinae) include complex baculum and entoglossal process of hyoid absent. Other possible sigmo- dontine synapomorphies given different outgroup topologies (e.g., monophyletic neotomine-pero- myscines) would include dual articulation of the first rib with the transverse processes of the sev- enth cervical and first thoracic vertebrae, fifth metatarsal not posterior to cuboid/calcaneum ar- ticulation, entepicondylar foramen of humerus ab- sent, supertrochlear foramen of humerus present, and a gap between trochlear process and articular facet of the calcaneum. Neither the weighted nor the unweighted anal- yses show a monophyletic Neotominae, but they do strongly support a monophyletic tylomyine group sensu Carleton ( 1 980) and Reig ( 1 984), Nyc- tomys and Tylomys. This pairing is found in 92% of bootstrap replicates (Fig. 21) and is supported by the following putative synapomorphies: no pa- rietal/occipital contact, squamosal fold, preputial glands present, overhanging supraorbital, subs- quamosal foramen absent, stapedial branch of the carotid artery reduced or absent, more than 30 caudal vertebrae, and gallbladder absent. All these character states are found in Ototylomys as well except a squamosal fold; the presence of preputials and gallbladder in Ototylomys is unknown. Oto- nyctomys was not examined. Absence of subsqua- mosal foramen and reduction of carotid circula- tion can also be found in Neotoma. Four steps are required to collapse the branch joining the tylo- myines and forming a trichotomy with Neotoma. The phylogenetic analysis identifies two well- defined branches within the Sigmodontinae tree, ichthyomyines and the oryzomyines sensu Voss and Carleton (1993), including the tetralophodont genera Holochilus, Pseudoryzomys, and Zygodon- tomys (Fig. 19). Monophyly of the ichthyomyines has already been established (Voss, 1 988), but this study more directly tests monophyly by placing the ichthyomyines in a broader cladistic analysis. In the bootstrap analysis weighted to favor sig- modontine monophyly (Fig. 21), Ichthyomyini is found in 97% of replicates. Trees five steps long- er than the most-parsimonious trees (with or with- out a dummy variable) must be examined before a nonmonophyletic Ichthyomyini is found. Ich- thyomyine monophyly is supported by nasals that extend posterior to lachrymal, masseteric tuber- cles, small or very small pinnae, and reduced gas- tric glandular epithelium. Sensitivity analyses demonstrate that, although the ichthyomyines are most commonly placed in a clade with other te- tralophodont groups, the akodontines and phyllo- tines, the sister-group to the ichthyomyines is sometimes the oryzomyines or a thomasomyine. It appears that the ichthyomyines occupy a rela- tively basal position in the sigmodontine tree. The oryzomyine taxa, exclusive of the thoma- somyines, form the second major clade. Support- ing the oryzomyines sensu stricto are the putative synapomorphies of nasals extending posterior to lachrymal (except in some Oryzomys), alisphen- oid strut absent, long palate (except in Holochilus), eight or more mammae, 1 2 thoracic vertebrae (ex- cept in Neacomys), fewer than 36 caudal verte- brae, hemal arch present, and gallbladder absent. The distribution of some of these potentially di- agnostic characters is explored in greater taxonom- ic detail in Table 6. The most-parsimonious trees given sigmodontine monophyly (Fig. 19) place Wiedomys as the sister-group to the oryzomyines. In this hypothesis, absence of the alisphenoid strut, 1 2 ribs, and possibly presence of the hemal arch (weakly developed in Wiedomys) would be synap- omorphies of the more inclusive clade. However, the bootstrap consensus places Chilomys as the sister taxon to Oryzomyini, indicating that the sis- ter-group to Oryzomyini is unresolved. Two ad- ditional steps are needed to draw the putatively basal oryzomyines (Oligoryzomys or Neacomys) out of the oryzomyines. Three additional steps are needed to disrupt oryzomyine monophyly when Fig. 20. Strict consensus cladogram of the 28 equally most-parsimonious trees of the South American Sigmo- dontinae, without a dummy variable. Overall length for each tree is 282 steps. The South African-endemic Mystromys is placed among the phyllotines, and the neotomine-peromyscine Scotinomys is placed near the base of the sigmo- dontines. Outgroup taxa are underlined. STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 57 ■30- r46- ■ 17- 39H 46 £ 1-13- { 11 { 83 16 r-9- ft 31- { 27 r m ■ 22. 36 r57- ■ 22- »{ ■38H 52 ■ 28- { 31- 83-I 19 • 4e\ Oryzomys capito Oryzomys palustris Nectomys squamipes l Zygodontomys brevicauda l — Holochilus bras iliens is Pseudoryzomys simplex Oligoryzomys fulvescens Neacomys spinosus Chilomys instans ■ Akodon boliviensis 1 — Akodon albiventer Oxymycterus hispidus Scapteromys turn id us Kunsia tomentosus Sigmodon hispidus Reithrodon auritus Graomys griseoflavus Calomys callosus Phyllotis darwini Neotomys ebriosus Punomys lemminus Anotomys leander Ichthyomys hydrobates Neusticomys monticolus Thomasomys rhoadsi Wiedomys pyrrhorhinos Rhipidomys latimanus Thomasomys aureus Thomasomys baeops Scotinomys teguina l Ochrotomys nuttalli 1 Peromyscus leucopus Tylomys nudicaudus Nyctomys sumichrasti Neotoma floridana j Cricetulus migratorius 1— Mesocricetus auratus Phodopus sungorus Calomyscus baluchi Mystromys albicaudatus 52 42 ■41 92 54 58 FIELDIANA: ZOOLOGY Oligoryzomys and Neacomys are excluded from the analysis. The root of the sigmodontine tree is placed with- in the thomasomyines, which appear to be highly paraphyletic. However, the bootstrap percentages are lowest for this region of the tree (Fig. 21). This analysis suggests that Thomasomys is also para- phyletic and its members occupy basal positions on the tree. Four additional steps are needed to join T. rhoadsi with its congeners in a monophy- letic Thomasomys. However, placement of the sig- modontine root is unstable because most char- acters that are variable within the sigmodontines are also variable among the outgroups. The result of this is that character polarities determined by outgroup criteria are only as accurate as the out- group topology. Sensitivity analyses (not illustrat- ed) demonstrated that shifts in outgroup relation- ships had significant impact on the placement of the sigmodontine root. Among these various anal- yses, the topological relationships within the sig- modontine portion of the unrooted network were relatively stable. It was the placement of the root within that network that was most unstable. Thus, if the neotomine-peromyscines and tylomyines were sister-groups and the Old World "cricetids" were paraphyletic, then the morphology of the an- cestral sigmodontine would most closely resemble the Old World "cricetids," and the sigmodontine root would be placed just outside the phyllotine group. If the tylomyines were the sister-group to the sigmodontines, then the root would be placed near the base of the oryzomyines. In most rooting alternatives, though, the thomasomyines were still paraphyletic and generally basal. The remaining branch with the most character support is that consisting of akodontines, scapter- omyines, phyllotines, Sigmodon, and Punomys, and is the sister-group to the ichthyomyines in Figure 19. I will refer to it by the shorter name of the tetralophodont tribal-group because it is com- prised by most of the taxa hypothesized by Hersh- kovitz to be derived from tetralophodont stock (i.e., lacking a complete mesolophostyle). The is- sue of Sigmodon is addressed separately below. This clade is supported by the following putative synapomorphies, as hypothesized from the map- ping of character transformations on the tree: in- cisive foramina extending to the molars, deep zygomatic notch, reduction to fewer than 30 cau- dal vertebrae (with hypothesized subsequent in- crease), and eight or more mammae. If the ich- thyomyines are not the immediate sister-group to the tetralophodont tribal-group, then reduction or partial fusion of the mesolophostyle would also be a supporting character. The tetralophodont tribal- group is also generally characterized by the ple- siomorphic presence of a gallbladder, a stapedial artery imparting a squamosal groove, moderately haired heels, nonoverhanging supraorbital surface, 1 3 thoracic rib pairs (with subsequent reduction), no hemal arch, and relatively small M3 (with en- largement among the phyllotines). Bootstrap per- centages for this clade are very low (Fig. 21). Within the tetralophodont tribal-group, Scap- teromyini (Hershkovitz, 1966), which includes Scapteromys and Kunsia, appears polyphyletic, and an Akodontini that includes the oxymycterines (sensu Reig, 1987) without the scapteromyines may be either paraphyletic (bootstrap consensus tree) or polyphyletic (most-parsimonious trees). How- ever, only one additional step is needed to be con- sistent with a monophyletic Akodontini (Akodon plus Oxymycterus). Two additional steps are need- ed for a monophyletic Scapteromyini. Punomys is placed as the sister taxon to the phyllotines plus Sigmodon. Monophyly of the phyllotines as currently de- fined is not directly supported. This analysis places Sigmodon within the phyllotine radiation. Three additional steps are needed to bring Sigmodon down to the immediate sister taxon to the phyl- lotines. In that topology, Punomys is placed as the sister taxon to Oxymycterus in an akodontine clade. In the most-parsimonious trees (Fig. 19), Sigo- modon, Reithrodon, and Neotomys have the lon- gest branch lengths among the terminal sigmo- dontine taxa. Characters that support a phyllotine plus Sigmodon clade (or a phyllotine clade with Sigmodon excluded) include complete loss of the mesoloph, premaxillaries subequal in extent with nasals, large sphenopalatine vacuity, mesoptery- goid narrower than parapterygoid, and large pin- nae (except Neotomys). The clade of Punomys plus the phyllotines is supported by a zygomatic arch inserting at a moderate to high position on the rostrum and a moderately long interparietal. Traditional notions of a Sigmodontini (Reig, Fig. 2 1 . Majority-rule bootstrap consensus tree ( 1 00 replicates) for the Sigmodontinae, including dummy variable weighted to favor sigmodontine monophyly. Numbers indicate percentage of replicates containing the specified clades. STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 59 1980) are not supported. The shortest trees that place Sigmodon and Holochilus as sister taxa are six steps longer than the most-parsimonious trees. Notably, those constrained trees move Sigmodon into the oryzomyines while leaving the rest of the tree nearly unchanged. The shortest trees that in- clude a Sigmodontini sensu Hershkovitz (1955; Sigmodon, Holochilus, Reithrodon, Neotomys) are 1 1 steps longer. In those alternative trees, the weight of Reithrodon and Neotomys draws Holochilus into a terminal phyllotine branch. Discussion Three principal conclusions can be drawn from the sigmodontine analysis. First, the Oryzomyini (Voss & Carleton, 1993), which includes the te- tralophodont genera Holochilus, Pseudoryzomys, and Zygodontomys, but which excludes the tho- masomyines, is confirmed. Second, the phyllotines are members of a tetralophodont tribal-group that includes the akodontines, scapteromyines, and Punomys. Third, the root of the sigmodontines is placed within the thomasomyine group. Mono- phyly of the Sigmodontinae is indicated given res- ervations regarding Mystromys and Scotinomys. Additionally, the monophyly of the Ichthyomyini and Tylomyinae is strongly supported. A problem for any sigmodontine phylogeny giv- en the current state of muroid systematics is the rooting of the tree. Many workers have taken the position that the oryzomyines or thomasomyines are the basal sigmodontines (Gardner & Patton, 1976; Hershkovitz, 1962, 1993; Reig, 1980, 1986), partially because oryzomyines sensu lato are char- acterized by many traits considered widespread and potentially plesiomorphic among other cri- cetine or murid rodents. Phyllotines have been considered by neontologists to be highly derived (Hershkovitz, 1962; Reig, 1986). However, Jacobs and Lindsay ( 1 984) concluded that phyllotines were primitive among sigmodontines, based almost en- tirely on the identification of Bensonomys, the old- est putatively sigmodontine fossils, as a subgenus of Calomys. Their hypotheses of primitive traits among sigmodontines are merely those of Ben- sonomys (Jacobs & Lindsay, 1 984, Table2) but are limited to molar and lower mandible characters, the only characters observable from the fossils. In contrast, this study found few dental characters (only three were included) that were informative at the tribal to subfamily level, and rooting of the sigmodontine radiation based on a few dental characters seems prone to mislead. Additionally, most of the Bensonomys fossils cannot be a Cal- omys as the genus is currently defined (Steppan, 1993); they possess mesolophs that are entirely absent among all extant Calomys and in the sister- group to Calomys, the remaining phyllotines. This argument does not preclude the possibility that prephyllotine ancestors or their relatives may have possessed reduced mesolophs. The placement of Chilomys is unstable, and in the past it has been placed either with the tho- masomyines (Hershkovitz, 1966a; Voss, 1991) or with the oryzomyines sensu stricto (Reig, 1980, 1986; Voss & Linzey, 1981). The proper status of the Wiedomyini is difficult to assess from this analysis, but Wiedomys does not appear to be far derived from a basal "thomasomyine" grade. Voss (1993) argued that formally maintaining genera in the tribe Thomasomyini was unjustifi- able owing to their collective lack of unifying, apo- morphic characters and the inability to assign in- dividual "thomasomyine" genera to other demonstrable monophyletic groups. As an alter- native, he recommended referring to thomaso- myines formally as a "plesion," citing Wiley (1 98 1) for comparison, to emphasize that they share primitive attributes. Wiley (1981, p. 219) explic- itly reserved the nonranked category "plesion" for fossil taxa, allowing them to be classified with Re- cent taxa without revising established classifica- tions for either the fossil or Recent taxa. The study strongly supports a tylomyine group that includes Nyctomys, Tylomys, and Ototylomys (and presumably Otonyctomys, which was not ex- amined). While this study groups the tylomyines with Neotoma, other studies indicate that the ty- lomyines are basal members of a New World ra- diation with no clear affinities to either the sig- modontines or neotomine-peromyscines (Carleton, 1980;Sarich, 1985; Haiduketal., 1988; Catzeflis et al., 1993). Using G-banded chromo- somes, Haiduk et al. (1988) suggested that Nyc- tomys was a basal member of a neotomine radi- ation after its separation from the South American sigmodontines. However, because the sigmodon- tines available for comparison constituted a tax- onomically biased and incomplete sample, in- cluding only oryzomyines and Sigmodon, suggested relationships to the sigmodontines as a whole must be tentative at best. The monophyly and basal phylogenetic position of the tylomyines should be recognized formally. Tribal status as the Tylo- myini (Carleton, 1980) would be most in keeping 60 FIELDIANA: ZOOLOGY with the results of this study (tylomyines as sister- group to Neotoma), but the available molecular studies suggest that elevating the tylomyines to an equal status with the sigmodontines and neotom- ine-peromyscines as the subfamily Tylomyinae (sensu Reig, 1984) would be more generally con- sistent. This analysis is generally at odds with the re- lationships and evolutionary tendencies in chro- mosomal evolution proposed by Gardner and Pat- ton (1976). They hypothesized that chromosome change was unidirectional, dominated by Robert- sonian fusions that reduced diploid number. Par- tially as a consequence of their model, the genus Oryzomys was proposed to be the stem group from which all sigmodontines arose. This analysis clear- ly shows that Oryzomys is a member of a derived clade separated from all other sigmodontine tribes. Nor is Oryzomys the basal member of the ory- zomyine clade, although the genus as currently constituted is probably not monophyletic. Gard- ner and Patton (1976) also hypothesized that Ho- lochilus was derived from a phyllotine stock; it is clearly an oryzomyine. Akodontines were dia- grammed as independently derived from Oryzo- mys (Gardner & Patton, 1976, Fig. 10), while this study indicates that the akodontines are related to the phyllotines and scapteromyines. Even a cur- sory mapping of diploid numbers on the trees from this study indicates that Robertsonian fusion can- not be used as the exclusive model of chromosom- al evolution in sigmodontines. Gardner and Pat- ton's model (which has also been proposed by Bianchi et al. [1971] and Pearson and Patton [1976]) has been salutary, but it has unfortunately sometimes been evoked as a phylogenetic axiom to polarize phylogenetic relationships (e.g., Vitullo etal., 1990). The previous discussion has referred to Sig- modon as an entity separate from the phyllotines despite its placement in Figure 19. There are three reasons for believing that the results of the phy- logenetic study shown in Figure 1 9 are misleading in regard to Sigmodon. First, three independent molecular data sets place Sigmodon outside any clade formed by the remaining sigmodontines. DNA hybridization places Sigmodon outside a clade that includes Oryzomys, Zygodontomys, Akodon, and Phyllotis (Catzeflis et al., 1993). Pro- tein immunological distances place Sigmodon as the outgroup to all the other sigmodontines (Sar- ich, 1985), while the rest of the immunological tree (Fig. 1 ) is in general agreement with this study. Electrophoretic allele data analyzed phenetically (Spotorno, 1986) (Fig. 5 A) and cladistically (Fig. 5B, reanalysis of data in Spotorno, 1986) place Sigmodon among the North American neoto- mine-peromyscines. Second, when Sigmodon is included in the phyllotine data set (results not shown), three discordant alternative placements for Sigmodon are represented among the most- parsimonious trees. Sixty percent of most-parsi- monious trees include Sigmodon, with 27% placing Sigmodon as the sister-taxon to the phyllotines plus akodontines and 13% placing Sigmodon as the basal oryzomyine. The last two alternatives push Graomys to a basal position among the phyl- lotines, in contrast to its typical terminal position (Steppan, 1993). The placement of Sigmodon among the phyllotines in the sigmodontine anal- ysis may be due to the taxa sampled and the char- acters included. For example, three of the five phyllotines in this sigmodontine analysis possess 1 2 ribs (Calomys, Graomys, Reithrodon), which is most-parsimoniously hypothesized as a synapo- morphy joining them with Sigmodon. However, this results from the improbable sampling of three independent rib losses from the both common and plesiomorphic phyllotine condition (Steppan, 1993). Likewise, Sigmodon, Graomys, and Reith- rodon are associated in this analysis by the pres- ence of an alisphenoid strut, but the strut appears to be independently evolved in Graomys and Reithrodon (Steppan, 1993). Sigmodon possesses the posteriorly divergent, ledged supraorbital re- gion found in some oryzomyines, Andalgalomys, and Graomys, but that is very different from the narrow and vertically ridged supraorbitals of Reithrodon and Neotomys. Third, Sigmodon lacks an angled premaxillo-maxillary suture, a syna- pomorphy that joins Reithrodon, Neotomys, and Euneomys and is unique to them (Steppan, 1993), and also lacks grooved incisors (except S. alstoni), another putative synapomorphy of the Reithrodon group. Sigmodon and some Holochilus are apparently the only sigmodontines other than Calomys with more than eight mammae. This would seem to support the Sigmodontini sensu Reig ( 1 980). How- ever, the remaining characters do not support the Sigmodontini, and this analysis places Sigmodon and Holochilus far apart on the tree (Fig. 1 9) and requires an additional six steps to unite them. Ad- ditionally, albumin immunological cross-reac- tions between Sigmodon and Holochilus are much lower than in other intratribal comparisons (Sar- ich, 1985). On the basis of the results here, and consistent STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 61 with the frequently suggested but rarely acted upon observations of previous workers (Gardner & Pat- ton, 1976; Hooper & Musser, 1964; Sarich, 1985; Voss & Myers, 1991), Holochilus should be re- moved from the Sigmodontini, leaving only Sig- modon. These various analyses disagree so strong- ly on the position of Sigmodon that it seems best to draw no conclusions at this time on its rela- tionships. Thus, if Sigmodontini is retained as a separate tribe, it should be considered Sigmodon- tinae incertae sedis, or even Muridae incertae sed- is. An interesting series of patterns is developed with characters that involve gain or loss, and in particular gain or loss of discrete structures, as opposed to topological conformation of parts. Among characters that show significant homopla- sy (i.e., multiple observations of evolutionary transformations), structures that are lost generally are not regained. Gallbladders, stapedial branch of the carotid artery, mesoloph(-id), and thoracic ribs all show a bias toward loss (or bias against reacquisition) based on character mapping and op- timization (accelerated transformation, ACCT- RAN, and delayed transformation, DELTRAN, options were both used). Unless otherwise noted, character transformations discussed below were hypothesized using both optimizations or by ACCTRAN, which disfavors the observation of directional bias in character transformations. Across the entire tree (and other records; Voss, 1991), the gallbladder is lost nine times (oryzo- myines, Ichthyomys, Rhipidomys, Ochrotomys, tylomyines, Cricetulus, Akodon cursor, Geoxus valdivianus) but never regained. Mesolophs are re- duced at least two times (tetralophodont tribal group plus ichthyomyines, ancestor of Holochilus, Pseudoryzomys, and Zygodontomys) and entirely lost three to four times (phyllotines, some ichthyo- myines, Sigmodon, Holochilus), but (depending on phylogenetic resolution) only gained to a poorly developed condition in Anotomys, maybe some akodontines not included here, and originally in an ancestor to the sigmodontines. The stapedial branch of the carotid artery shows at least seven reductions or losses among sigmodontines (ory- zomyines, Thomasomys/ Rhipidomys clade, some ichthyomyines, Reithrodon, Sigmodon, Neoto- mys, Chilomys), but, depending on relationships within the oryzomyines and under ACCTRAN optimization, only three reversals (Neacomys, Neusticomys, Zygodontomys). Under DELTRAN optimization, there are nine reductions in carotid circulation and only one reversal {Zygodontomys). Similarly, ribs show six losses (given phyllotine phylogeny of Steppan [1993] and data in Table 5; Sigmodon, Calomys, Graomys, Reithrodon, Rhip- idomys, and oryzomyines plus Wiedomys) versus two gains (Anotomys and Neacomys). In contrast, mammae number shows at least five increases (sigmodontines, tetralophodont tribal- group, oryzomyines, Calomys, Holochilus, Sig- modon) versus one to two reductions (Scotinomys, tylomyines plus Neotoma). Given this tree topol- ogy, alisphenoid strut (four gains, four losses) and caudal vertebrae (approximately five gains, five losses) do not show a bias. Somewhat surprisingly, the quantitative character pinna size shows seven to eight reductions versus one (phyllotines) to three (Neusticomys, Thomasomys baeops) enlarge- ments, depending on resolution of polytomies. The preponderance of pinna reduction over enlarge- ment may in part be an artifact of the particular selection of character states. Phyllotine Monophyly Because of the placement of Sigmodon within the phyllotines, this study does not provide strong support for the monophyly of the tribe Phyllotini. However, if the molecular studies are correct in placing Sigmodon in a basal position among the sigmodontines, then its placement among the phyllotines in this study may be due to conver- gence and the absence of any taxa along the Sig- modon lineage to provide evidence for character transformations, thus leaving Sigmodon with a very long branch length. Very long branches due to in- sufficient taxonomic sampling can lead to erro- neous groupings (Felsenstein, 1978; Huelsenbeck & Hillis, 1 993). Forced removal of Sigmodon does not affect the remaining hypothesized relation- ships. Therefore, I define the Phyllotini as the common ancestor of the following genera and all its descendants: Andalgalomys, Andinomys, Au- liscomys, Calomys, Chinchillula, Eligmodontia, Euneomys, Galenomys, Graomys, Irenomys, Neo- tomys, Phyllotis, and Reithrodon. Punomys does not appear to be a phyllotine, but in a taxonom- ically more focused study (Steppan, 1993) Puno- mys is equivocally associated with some phyllo- tine taxa. I therefore agree with the conclusions of Olds and Anderson (1989) on the content of Phyl- lotini, with the single exception of not including Punomys. Diagnostic synapomorphies for the Phyllotini are moderate or large pinnae (> 0.15 head and body length), parapterygoid fossa rela- 62 FIELDIANA: ZOOLOGY tively broader than mesopterygoid fossa, very open sphenopalatine vacuities, complete loss of the me- soloph, posterior extensions of premaxillaries and nasals subequal, and (except Calomys) two pairs of preputial glands. In contrast, the following char- acter states hypothesized by Olds and Anderson (1989) to be phyllotine synapomorphies instead appear to be plesiomorphic: hairy heel, palate long, incisive foramina long, supraorbital region never evenly curved in cross-section, interparietal well developed, zygomatic notch deeply excised, teeth tetralophodont (which includes vestigial meso- lophs [Olds & Anderson, 1989]), and M3 more than half the length of M2. A formal diagnosis is presented in the Taxonomy section. Although most recent studies have excluded Pseudoryzomys from the phyllotines (e.g., Olds & Anderson, 1989; Voss & Myers, 1991; Voss & Carleton, 1993), others have included it (Braun, 1993; Reig, 1986). I agree with Voss and Carleton (1993) on moving Pseudoryzomys to the Oryzo- myini. Other oryzomyines (e.g., Microakodonto- mys, Oligoryzomys sp., Hershkovitz, 1993) exhib- it reduction and loss of the mesoloph(-id) in association with the transition from forest to grass- land and scrub communities (Hershkovitz, 1993). Braun (1993) concluded from a cladistic analysis that Pseudoryzomys is either the basal phyllotine or the sister taxon to the phyllotines. Her study included two oryzomyine and one thomasomyine species in the outgroups, but these were used to define ancestral states and were not included in the actual numerical analysis. Thus, intentionally or not, Pseudoryzomys was assumed a priori to be a member of a clade that included the phyllotines and the other outgroups, two species of Akodon. With only two closely related Akodon remaining as outgroups to the phyllotines, the analysis could not test the tribal relationships of Pseudoryzomys or the monophyly of the phyllotines. This analysis demonstrates that Pseudoryzomys is unrelated to the phyllotines: at least 10 additional steps are required to place it as a basal phyllotine or among the tetralophodont tribal-group. Phylogenetic Relationships within Phyllotini Results As should be expected, the results of this anal- ysis conform closely to those produced earlier (Steppan, 1993), using nearly the same data set (see Materials and Methods). While the most-par- simonious trees place Punomys in a clade with Andinomys and Irenomys (Fig. 22, strict consen- sus), trees only one step longer place Punomys outside the phyllotines (Fig. 23, 80% majority rule consensus). In Steppan (1993), these alternative topologies were equally parsimonious, and the nonphyllotine hypothesis for Punomys was pre- ferred. The 200 replicate bootstrap analysis with this data set (Fig. 24) also places Punomys as the sister taxon to the phyllotines, the same as in the sigmodontine analysis. The root was placed be- tween Thomasomys and the oryzomyines by des- ignating Thomasomys as the outgroup. Details of character support for specific nodes can be found in Steppan (1993). Differences be- tween the two sets of analyses and principal areas of congruence will be highlighted here. Selected nodes are labeled on Figure 23 for references in the text. This analysis results in 22 equally most-parsi- monious trees, each 763 steps long, with a CI of 0.22 and an RI of 0.55 (Fig. 22, strict consensus). Excluding the outgroups, the trees are 525 steps long, CI = 0.29, RI = 0.57. Both sets of CIs are at the mean of the observed range of values for this many taxa (Archie, 1 989) or somewhat below the "expected" value of 0.34 for 47 taxa (Sander- son & Donoghue, 1 989). In each of the 1 2 1 equally most-parsimonious trees that do not include Pu- nomys within the phyllotines (Fig. 23, 80% ma- jority rule consensus), the respective values are 764 steps long, CI = 0.22, RI = 0.55 overall, and 498 steps long, CI = 0.30, RI = 0.58 excluding outgroups. Both sets of trees are of equal length when Punomys is pruned from the trees. Based on the arguments from the sigmodontine analysis and in Steppan (1993), the alternative hypothesis of a nonphyllotine Punomys will form the basis for the remaining analyses and discussion, as well as cal- culating CIs and RIs for individual characters (Ta- ble 8). The differences between the preferred hypoth- esis from this analysis and Steppan (1993, Fig. 1) are minor and limited to several collapsed branch- es due to the greater number of trees in this anal- ysis and the exclusion of two taxa {species nova, northern populations of Andinomys edax) includ- ed in the earlier study. The major difference be- tween the two studies is greater character support in this analysis as reflected in higher average boot- strap percentages (46% in Fig. 24 versus 41% in Steppan [1993, Fig 3]). STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 63 Calomys callosus Calomys hummelincki Calomys laucha Calomys lepidus Calomys sorellus Andalgalomys pearsoni Graomys griseoflavus Graomys domorum Eligmodontia morgani Phyllotis gerbillus Phyllotis amicus Phyllotis darwini Phyllotis xanthopygus xanthopygus Phyllotis xanthopygus rupestris Phyllotis caprinus Phyllotis magister Phyllotis osilae Phyllotis haggard! Phyllotis definitus Phyllotis andium Phyllotis wolffsohni Chinchillula sahamae Galenomys garleppi Auliscomys boliviensis Auliscomys sublimis Auliscomys p ictus Euneomys chinchilloides Euneomys petersoni Reithrodon typicus Reithrodon auritus pachycephalus Reithrodon auritus evae Neotomys ebriosus Loxodontomys micropus Irenomys tarsal is Andinomys edax Punomys lemminus Akodon albiventer Akodon boliviensis Chroeomys an din us Oxymycterus hispidus Ichthyomys hydrobates Scapteromys turn id us Holochilus brasi lien sis Pseudoryzomys simplex Zygodontomys brevicauda Nectomys squamipes Thomasomys baeops Fig. 22. Strict consensus cladogram of 22 equally most-parsimonious trees for the Phyllotini (763 steps long overall, CI = 0.22, RI = 0.55). Thomasomys and the four oryzomyine taxa (Holochilus, Nectomys, Pseudoryzomys, Zygodontomys) were designated as outgroups. Punomys is placed among the phyllotines with Andinomys and Ir- enomys. 64 FIELDIANA: ZOOLOGY Calomys callosus Calomys hummelincki Calomys laucha Calomys lepidus Calomys sorellus Andalgalomys pearsoni Graomys griseoflavus Graomys domorum Eligmodontia morgan! Phyllotis gerbillus Phyllotis amicus Phyllotis darwini Phyllotis xanthopygus xanthopygus Phyllotis xanthopygus rupestris Phyllotis caprinus Phyllotis magister Phyllotis osilae Phyllotis haggard! Phyllotis definitus Phyllotis andium Galenomys garleppi Auliscomys boliviensis Auliscomys sublimis Auliscomys pictus Euneomys chinchilloides Euneomys petersoni Reithrodon typicus Reithrodon auritus pachycephalus Reithrodon auritus evae Neotomys ebriosus Loxodontomys micropus Irenomys tarsalis Andinomys edax Chinchillula sahamae Phyllotis wolffsohni Punomys lemminus Akodon albiventer Akodon boliviensis Chroeomys andinus Oxymycterus hispidus Scapteromys turn id us Ichthyomys hydrobates Holochilus brasiliensis Pseudoryzomys simplex Zygodontomys brevicauda Nectomys squamipes Thomasomys baeops Fig. 23. Eighty percent majority-rule consensus tree of 121 equally most-parsimonious trees wherein Punomys is not a phyllotine. Each tree is one step longer than the most-parsimonious overall (764 steps long overall; excluding outgroups, each tree is 498 steps long, CI = 0.30, RI = 0.58). This topology represents the preferred hypothesis of phylogenetic relationships among the phyllotines. Labeled nodes are referred to in the text. STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 65 • — 21- 1—39- i — 31 1—53- | — 32-1 ■26- I— r— 74 43 t_ ,—24. 1—20' 1—12- ■38 r"C 84J ■57 r 2 C . — 68-^ I — 41 I — 16 i&T ,£ 84-i 1—35' 5- ■ 84. 94- | 9ft ] I — 76 -10O| 83H r£ 30 r 2 t ■ 20- I— 35 c 64- .ssT •c 5{ Calomys callosus Calomys hummelincki Calomys laucha Calomys lepidus Calomys sorellus Andalgalomys pearsoni Graomys griseoflavus Graomys domorum Eligmodontia morgani Phyllotis amicus Phyllotis gerbillus Phyllotis andium Phyllotis darwini Phyllotis caprinus Phyllotis xanthopygus xanthopygus Phyllotis xanthopygus rupestris Phyllotis definitus Phyllotis magister Phyllotis osilae Phyllotis haggard! Galenomys garleppi Auliscomys bo I Mens is Auliscomys sublimis Auliscomys pictus Euneomys chinchilloides Euneomys petersoni Reithrodon typicus Reithrodon auritus pachycephalus Reithrodon auritus evae Neotomys ebriosus Loxodontomys micropus Irenomys tarsalis Andinomys edax Chinchillula sahamae Phyllotis wolffsohni Punomys lemminus Akodon albiventer Akodon boliviensis Oxymycterus hispidus Chroeomys andinus Scapteromys tumidus Ichthyomys hydrobates Nectomys squamipes Holochilus brasiliensis Pseudoryzomys simplex Zygodontomys brevicauda Thomasomys baeops Fig. 24. Majority-rule bootstrap consensus tree (200 replicates) for the Phyllotini. Numbers indicate percentage of replicates containing the specified clades. 66 FIELDIANA: ZOOLOGY Calomys is paraphyletic in the majority of the most-parsimonious trees with C. sorellus as the sister taxon to the remaining phyllotines. The sta- tus of Calomys sorellus and C. lepidus is unre- solved. Support for paraphyly (or monophyly) of Calomys is weak: the bootstrap tree (Fig. 24) in- dicates a monophyletic Calomys but in only 26% of bootstrap replicates. The placement of C. so- rellus with the remaining phyllotines is supported by a ventral pair of preputial glands (97), loss of the parastyle/anteroflexus Ml (12), more than 25 caudal vertebrae (80), and long interparietal (56). The basal nodes of the remaining phyllotines are unresolved in the preferred hypothesis (Fig. 23) but are resolved in the analysis with Punomys in the ingroup (Fig. 22) and in the previous anal- ysis (Steppan, 1993). All analyses reveal four clades among the taxa terminal from Calomys. These include a Phyllotisl Graomys clade (node B), an Auliscomys group (node E), a clade including Reithrodon and Loxodontomys (node F), and the sister taxa Andinomys and Irenomys. The last three clades form part of the sister-group to the Phyl- lotisl Graomys clade in Figure 22. This clade, in- cluding Reithrodon and Auliscomys, is much more highly differentiated, as reflected in the greater ge- neric diversity as currently recognized (nine genera versus four). The bootstrap consensus tree joins Phyllotis sen- su stricto with the clade containing Graomys and Eligmodontia, but this node is not fully resolved in the consensus of the most-parsimonious trees (Fig. 23, above node B). In any case, Phyllotis is shown to be polyphyletic. In addition to the core Phyllotis clade (node D), other species currently included in Phyllotis are basal members of clades with Eligmodontia and Graomys (P. amicus, P. gerbillus), Auliscomys and Reithrodon groups (P. wolffsohni), and a more inclusive clade (node B, P. andium). Bootstrap percentages for all these groupings are low, however, as Phyllotis occupies the most poorly resolved region of the tree. Eight additional steps are needed for a monophyletic Phyllotis. Furthermore, five additional steps are needed just to bring andium and wolffsohni into a Phyllotis clade while still leaving amicus and gerbillus at the base of the Graomys clade. Char- acters supporting the inclusion of P. wolffsohni at the base of the Reithrodon and Auliscomys groups include a nonlinear, "Y"- or "comma"-shaped fis- sure in the upper incisors (3), premaxillaries ter- minating behind the anterior edge of the incisors (37), and subequal mesopterygoid and parapter- ygoid fossae widths (64). Sensitivity analyses in- dicate that despite low bootstrap percentages, Phyllotis sensu stricto (node D) is moderately sta- ble. Phyllotis sensu stricto is supported by a mod- erate to large distal baculum (93) and a series of homoplasious characters. The highest bootstrap percentage for any Phyl- lotis node that is also found in Figure 23 is 68%, for the clade consisting of P. darwini, P. caprinus, and the two subspecies of P. xanthopygus. Char- acter support for this xanthopygus species-group is principally provided by three phallic characters: hooks on the lateral mounds (95), dorsal knobs on the lateral mounds (96), and a large distal baculum relative to proximal baculum (93). The bootstrap percentage is 48% for the clade of P. magister and P. definitus, two very restricted and geographically distant taxa that had been considered conspecific by Pearson (1958), but P. magister is placed as the sister-species to the xanthopygus species-group in the most-parsimonious trees (Figs. 22, 23). Spe- cific character support for sister-species status is weak but includes nasals slightly broader than minimum interorbital distance (48, CI = 0.17 overall, but character state unique within the Phyl- lotis clade) and pectoral streaks (9 1 , CI = 0. 1 7). The Graomys/ Andalgalomys clade is placed as the sister-group to Eligmodontia (node C), though this grouping is not as well supported as the Gra- omys/ Andalgalomys clade in the bootstrap tree. Phyllotis gerbillus and P. amicus next join succes- sively to this group in the shortest trees (Fig. 23) or as a sister clade in the bootstrap consensus tree (Fig. 24). This more inclusive clade is supported by a posteriorly divergent supraorbital (50) and premaxillaries protruded well anterior to the in- cisive plane (37). The clade consisting of Graomys and Andal- galomys is supported by orbital wings of the pre- sphenoid posterior to maximum constriction of the presphenoid (69), a small but distinct zygo- matic spine (43), a sharply ridged, overhanging supraorbital region (50), a laterally apressed sta- pedial spine (59), and 12 ribs (79). Paraphyly of Graomys with respect to Andalgalomys is strongly indicated as G. griseoflavus and A. pearsoni appear as sister-species. This pairing is found in 83% of bootstrap replicates and is supported by no hy- poflexus reduction M3 (23), no posterior shift of mesoflexus M3 (25), fusion of opposing flexi M3 (31), and flattening of hamular process (60). Four additional steps are needed for a monophyletic Graomys, as the sister taxon to Andalgalomys. Auliscomys pictus, A. sublimis, A. boliviensis, and Galenomys together compose the Auliscomys group STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 67 Table 8. Consistency and retention indexes for phyllotine characters. Number Character name CF RP 1. 2. 3 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. Incisor grooves Incisor procumbency Upper incisor dentine fissure Labial root of M 1 Labial root of M 1 Molar roots of M3 Labial root of m 1 Molar roots of m2 Molar roots of m3 Anteromedian flexus Ml Mesostyle M 1 Parastyle/anteroflexus M 1 Flexus penetration M 1 Anterolabial cingulum m 1 Protoflexid m 1 Cusp arrangement m 1 Anteromedian flexid ml Procingulum separation ml Posterolophid/stylid m 1 Posterolophid/stylid m3 Procingulum M2 Procingulum m2 Hypoflexus reduction M3 Reduction of mesoflexus M3 Posterior shift of mesoflexus M3 Hypoflexus lake M3 Rotation of flexus axes M3 Mesoflexid reduction m3 Anterior shift of mesoflexid m3 Posterior shift of hypoflexid m3 Fusion of opposing flexi in M3 Ratio of M3 length to alveolar length of molar tooth row Capsular projection of mandible Height of coronoid process Anterior masseteric ridge position Medioventral process of mandibular ramus Premaxillary protrusion Posterior extent of incisive foramina Maxillary septum of incisive foramina Orientation of incisive foramina Dorsoventral position of anterior root of zygomata Posterior margin of zygomatic plate Development of zygomatic spine Inclination of zygomatic plate Premaxillo-maxillary suture orientation Posterior extension of nasals Posterior extension of premaxillaries Nasal width Interorbital shape Supraorbital edge Supraorbital ridge Supraorbital knobs Mediodorsal fusion of frontals Shape of frontoparietal suture Angle of frontoparietal suture Medial length of interparietal/parietal Orientation of anterior border of auditory bulla Tegmen tympani Shape of stapedial spine of auditory bulla Thickness of hamular process of squamosal Positions of temporal vacuities 0.444 0.762 0.286 0.500 0.333 0.733 0.286 0.500 1.000 0/0 0.286 0.286 0.333 0.333 0.143 0.333 0.167 0.286 0.167 0.286 0.250 0.400 0.333 0.333 0.167 0.474 0.333 0.600 0.125 0.562 0.200 0.556 0.300 0.462 1.000 1.000 0.200 0.385 1.000 1.000 0.200 0.478 0.286 0.286 0.167 0.375 0.154 0.522 0.125 0.462 0.167 0.667 0.125 0.417 0.167 0.375 0.500 0.875 0.333 0.500 1.000 1.000 0.200 0.467 0.125 0.364 0.200 0.556 0.300 0.611 0.222 0.500 0.250 0.538 0.500 0.625 0.667]* [0.667]* 0.667 0.800 0.286 0.583 0.200 0.636 0.300 0.611 0.125 0.533 1.000 1.000 0.500 0.500 0.200 0.429 0.167 0.688 0.333 0.600 0.333 0.500 0.333 0.600 0.333 0.714 0.667 0.500 0.333 0.600 0.500 0.500 0.200 0.333 0.250 0.143 1.000 1.000 1.000 1.000 0.250 0.600 0.200 0.333 68 FIELDIANA: ZOOLOGY Table 8. Continued. Number Character name CI" RP 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77. 78. 79. 80. 81. 82. 83. 84. 85. 86. 87. 88. 89. 90. 91. 92. 93. 94. 95. 96. 97. 98. Internal carotid canal Extension of eustachian tube Relative width of mesopterygoid fossa Parapterygoid shape Shape of mesopterygoid fossa Parapterygoid fossa depth Sphenopalatine vacuities Position of orbital wings of presphenoid Anterior border of mesopterygoid fossa Medial process of posterior palate Posterior palatine ridge Posterolateral palatal pits Orientation of maxillary tooth rows Sphenopalatine foramen Carotid circulation Squamosal fenestra Alisphenoid strut Number of thoracic rib pairs Number of caudal vertebrae Neural spine of T2 Height of neural spine of C2 Length of neural spine of C2 Position of deltoid tuberosity Ventral surface of claws (manus) Length of Dl relative to D5 (pes) Position of hypothenar pad Furring of soles of feet (pes) Countershading of tail Furring of tail dorsum Body pelage pattern Pectoral streaks Distal/proximal bacular length Length of lateral mounds relative to medial mound Hooks on lateral mounds Knob on dorsal surface of lateral mounds Preputial glands Gallbladder 0.250 0.400 0.222 0.125 0.333 0.333 1.000 1.000 0.333 0.500 0.400 0.727 1.000 1.000 1.000 1.000 0.333 0.333 0.100 0.400 1.000 1.000 0.500 0.500 0.250 0.684 0.667 0.667 1.000 1.000 0.111 0.333 0.400 0.667 0.333 0.667 0.200 0.579 1.000 1.000 0.500 0.500 0.500 0.500 0.200 0.429 0.500 0.333 0.333 0.500 0.167 0.167 0.286 0.000 0.167 0.375 0.167 0.000 0.250 0.400 0.167 0.000 0.333 0.692 1.000 1.000 1.000 1.000 1.000 1.000 0.667 0.000 [1.000] [1.000] " Character indexes calculated over the phyllotine portion only of the consensus tree in Figure 23. * Indexes in brackets (e.g., [0.500]) were calculated over the entire tree, including outgroups, because the character was invariant or uninformative within the phyllotines. (node E), which excludes Loxodontomys micropus (usually considered an Auliscomys [Musser & Carleton, 1993; Simonetti & Spotorno, 1980]). The shortest tree that includes micropus within a monophyletic A uliscomys is nine steps longer than the shortest trees overall. Thus, this data set does not support the inclusion of micropus within an Auliscomys clade. Sister-species status for A. pictus and A. sublimis (94% of bootstrap replicates) is supported by the medial digit of the baculum much longer than the lateral digits (94), incisive forami- na extending to the level of the paracone and pro- tocone (38), ventral surface of foreclaws forming distinct keel (85), and upper incisors lightly grooved (1). The genus Auliscomys, excluding micropus, is characterized by upper incisors with fine striae or shallow grooves (1), supraorbital region anterior- ally divergent (49), reduction of labial root M 1 (4), and posterior shift of hypoflexid m3 (30). Sup- porting the node joining Galenomys with Aulis- comys are orthodont to weakly proodont incisors (2, CI = 0.29 overall, but character state unique among phyllotines), posterior extent of premax- illaries terminating anterior to nasals (47), and narrow mesopterygoid fossa (64). This clade is no longer monophyletic in some trees that are three steps longer than the most-parsimonious. This analysis does not support the suggested association between Galenomys and A. boliviensis (Braun, 1993): boliviensis is grouped with Galenomys in only 5% of bootstrap replicates versus 84% with sublimis and pictus. STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 69 Less stable is the position of Chinchillula. Sup- port for its placement at the base of the Auliscomys group (Fig. 22) comes from the anterior border of the zygomatic plate rounded or receding dorsally (43) and premaxillaries terminating behind the an- terior plane of the incisors (37). In the alternative hypothesis found in some of the most-parsimo- nious trees comprising Figure 23 and in the boot- strap consensus tree (Fig. 24), Chinchillula is basal to the Andinomys and Irenomys clade. The best supported of the generic-groups is the Reithrodon group (node F), previously defined by Olds and Anderson (1989), consisting of Reith- rodon, Neotomys, and Euneomys. Inclusion of Loxodontomys with the Reithrodon group is sup- ported by a relatively parallel-sided parapterygoid fossa (65), a tripartite fissure in the upper incisors (3), and a narrow mesopterygoid fossa (64) and is found in 35% of bootstrap replicates. The Reithrodon group is supported by a sharply angled premaxillo-maxillary suture (45, unique within the Sigmodontinae), sigmoidal molars, sen- su Hershkovitz (1955) (represented here by mul- tiple characters), no anterior shift by the meso- flexid m3 (29), distinctly grooved incisors (1), anterior root of the zygomata inserting high, close to dorsal surface of the rostrum (41), absence of labial root ml (7), and supraorbital knobs (52). The close relationship of Reithrodon with Neoto- mys is supported by loss of supraorbital branch of the stapedial artery (76), a deeply channeled pos- terior palate with distinct median ridge (72), an- terior apexes of incisive foramina well separated (40), and deeply excavated parapterygoid fossae (67). All the analyses place two genera not generally recognized by previous workers as closely related: Andinomys and Irenomys. Their grouping together is supported by an anterior masseteric ridge below and well posterior to the diastema (35, CI = 0.30 overall, but character state unique among the phyl- lotines), anterior apexes of incisive foramina rel- atively widely separated (40), frontals incomplete- ly fused or apparently vascularized along the midline (53), and posterolateral palatal pits in the anterior parapterygoid fossa (73). The bootstrap consensus tree (Fig. 24) groups the taxa in 30% of replicates. Discussion Comparisons between the results of this study and previous studies show only moderate agree- ment regarding suprageneric relationships, and that discordance may be due in part to the strictly cla- distic approach of this study in contrast to the evolutionary systematics of most prior studies. Some of the earlier studies (e.g., Hooper & Musser, 1964) make pairwise statements of similarity that are difficult to translate into a hierarchical phy- logenetic hypothesis, and others implicitly rely on paraphyletic groups. In his revision of the genus Phyllotis, Pearson (1958) found consensus with Ellerman (1941) and Osgood (1947) and recog- nized four subgenera — Graomys, Auliscomys, Loxodontomys, and Phyllotis— and removed P. gerbillus to the related genus Paralomys. The phy- logenetic relationships implied by placing these subgenera under Phyllotis is consistent with this study in regard to Graomys being closely related to Phyllotis but is incongruent in regard to Aulis- comys and Loxodontomys, which this study shows to be more closely related to other genera. Pearson (1958) also did not recognize Eligmodontia as part of a Phyllotis group. Hershkovitz (1962) revised the phyllotines and recognized a Calomys section, which could be a clade or a grade, and a Phyllotis section, which should translate as a clade. The Calomys section was primarily distinguished from the Phyllotis sec- tion by crested (bunodont) rather than flat or ter- raced molars. Zygodontomys from his Calomys section and Pseudoryzomys from his Phyllotis sec- tion have since been removed from the phyllo- tines. The remainder of his Calomys section con- sists of Calomys and Eligmodontia. Like Pearson (1958), he included Auliscomys and Graomys within the genus Phyllotis and indicated that Eu- neomys along with the sigmodonts (Reithrodon, Neotomys, Holochilus, and Sigmodori) might be considered the sister-groups to the phyllotines. Species-group assignments are more similar be- tween Hershkovitz ( 1 962) and this study; for ex- ample, Hershkovitz's P. darwini complex is al- most identical to the P. xanthopygus-magister species-group seen in this study. Pearson and Patton ( 1 976) and Spotorno ( 1 986) have diagrammed hypotheses of evolutionary re- lationships based on karyotypic data. Species that share the same diploid and fundamental numbers are generally also found by this analysis to be close- ly related— for example, A. pictus with A. sublimis, and P. xanthopygus and P. darwini with P. capri- nus. However, P. amicus and P. magister also share the same karyotypic formula but are morpholog- ically quite distinct. Similarly, P. haggardi and P. 70 FIELDIANA: ZOOLOGY gerbillus share their karyotypic formulas with the xanthopygus species-group. Higher-order rela- tionships show less comparability across the two data sets. For example, Spotorno (1986) placed Andinomys at the base of the phyllotine radiation, while the karyotypes of Reithrodon, Euneomys, and Neotomys are as diverse as those of the phyl- lotines as a whole and give no indication of close relationship. In fact, Spotorno (1986; p. 22) ex- plicitly acknowledged that gross karyotype is a poor estimator of homology, concluding from G-band- ing patterns that the close similarity of the P. xan- thopygus and Euneomys karyotypes "represent[s] independent acquisitions within each taxon." Spo- torno (1986) also screened electrophoretic alleles. His UPGMA dendrogram (Fig. 5 A) separates An- dinomys, Irenomys, and Euneomys from Reith- rodon and Loxodontomys by placing them near the base of the tree. A cladistic reanalysis of the same data set (Fig. 5B) provides little resolution. The electrophoretic data set in Spotorno (1986) does not seem to be highly informative for the phyllotines. Reig (1986) presented a biogeographic scenario for the diversification of the phyllotines and other sigmodontine groups. His scenario drew upon mo- lar morphology and its dietary correlates, ecology, karyology, biogeography, and the limited fossil ev- idence. Paraphrasing in cladistic terminology, Reig (1986) visualized Calomys as the most basal and generalized phyllotine genus, with C. sorellus as the most basal member of either a Calomys or phyllotines-minus-Ca/omysclade. His view of the lowland Calomys (e.g., C callosus, C. laucha) as derived or terminal species is consistent with this study. Phyllotis and a Neotomys-Sigmodon-Holo- chilus complex constitute the basal members among the remaining phyllotines and evolved in the central and southern altiplano. Auliscomys, Galenomys, and the sister taxa Chinchillula and Andinomys are then hypothesized to be indepen- dently evolved from a highly paraphyletic Phyl- lotis. In sharp contrast to the results of this study, Reig (1986) hypothesized that Graomys and Auliscomys are sister taxa. Andalgalomys, Pseu- doryzomys, and Eligmodontia would be indepen- dently derived from Calomys. Finally, Loxodonto- mys and Euneomys are independent southern offshoots of a paraphyletic Auliscomys. Thus, Gra- omys would be closely related to Euneomys and unrelated to Andalgalomys, while Reithrodon, Neotomys, and Euneomys would be unrelated to each other. Braun (1993) recently reported results of phe- netic and cladistic analyses of the phyllotines based on 36 craniodental and 10 external characters, re- corded as 39 qualitative and 7 quantitative char- acters. Qualitative and quantitative characters were equally influential in the analyses because of the large number of character states in all the quan- titative characters (8-10 each). Her cladogram shows some similarities to mine, although the ro- bustness of her cladistic results are unknown due to software limitations and the procedures used and because confidence estimates (e.g., bootstrap values or additional steps required to break up clades) were not reported. Character support for clades was not generally reported either. A prin- cipal conclusion was that Pseudoryzomys was the sister taxon to the phyllotines and, thus, may be the basal phyllotine. By only including the phyl- lotines, two akodonts, and Pseudoryzomys in the actual numerical analysis without any oryzo- myines, the tribal status of Pseudoryzomys could not be tested. The results of this study indicate that Pseudoryzomys is not a phyllotine, nor is it within a clade that includes the phyllotines and akodontines. From the results of these analyses, I propose several generic groups to provide an informal ref- erence structure to communicate some of the bet- ter supported hypotheses. The informal nomen- clature reflects the uncertainty regarding key nodes, some more inclusive than the generic-groups I pro- pose, that would allow a proper cladistic allocation of monophyletic groups to formal subtribes. The groups I recognize are the Graomys group (node C) including Andalgalomys, Graomys, and Elig- modontia; the Auliscomys group (node E) includ- ing Auliscomys and Galenomys; the Reithrodon group (node F) including Euneomys, Neotomys, and Reithrodon; and the Andinomys group in- cluding Andinomys and Irenomys. The species amicus and gerbillus, currently assigned to Phyl- lotis, are most likely basal members of the Gra- omys group and should be assigned to it provided future studies confirm that hypothesis. Loxodon- tomys may well be a basal member of the Reith- rodon group, but this study does not definitively demonstrate it. Chinchillula currently stands as Phyllotini sedis mutablis for nearly equally par- simonious placements at the base of the Aulisco- mys or Andinomys groups. Phyllotis as currently recognized is almost certainly paraphyletic, but the relevant region of the phylogeny is not sufficiently resolved that I can confidently propose an alter- STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 71 native hypothesis with which to formally revise the taxonomy. Finally, more confidence can now be placed in my earlier suggestion (Steppan, 1993) that, due to the paraphyly of Graomys, Andalga- lomys should be subsumed within it. I will also suggest, but not diagnose, a more formal taxonomy, primarily as a hypothesis to be tested by further studies and as a possible aid to description of the phylogenetic hypotheses pre- sented here. The most appropriate taxonomic cat- egory between genus and tribe would be the sub- tribe. To maximize information content and allow the use of both subtribes and generic groups in future taxonomies, recognized subtribes should be more inclusive than the generic groups that I just listed. In this scenario, the clade comprised min- imally of Phyllotis sensu stricto and the Graomys group would be subtribe Phyllotina (node B). The sister-group to Phyllotina would be Reithrodonina and is expected to include the Auliscomys, Andi- nomys, and Reithrodon groups. Finally, the sister- group to the clade combining Phyllotina and Reithrodonina would be Calomyina, including only Calomys, unless C. sorellus were in fact the sister- group to Phyllotina-plus-Reithrodonina, in which case sorellus would have to receive its own genus and possibly subtribe. Taxonomy Numbers in parentheses listed in the diagnoses refer to the character number from the phyloge- netic analysis of the phyllotines (Table 4). All di- agnoses are phylogenetic in nature, in that they list character states hypothesized to be derived relative to a named, more inclusive taxon. Asterisk (*) signifies autapomorphy relative to the other phyllotines. Tribe Phyllotini Vorontsov, 1959 Type Genus— Phyllotis, by tautonomy. Included TAXA—Andinomys, Calomys, Chin- chillula, Eligmodontia, Euneomys, Galenomys, Graomys, Irenomys, Loxodontomys, Neotomys, Phyllotis, and Reithrodon. Diagnosis— Members of the Neotropical sub- family Sigmodontinae (family Muridae) descend- ed from a common ancestor with the following traits: moderate or large pinnae (> 0. 1 5 head and body length), parapterygoid fossa relatively broad- er than mesopterygoid fossa, very open spheno- palatine vacuities, complete loss of the mesoloph, posterior extensions of premaxillaries and nasals subequal, and (except in some Calomys) two pairs of preputial glands. Calomys Waterhouse (Figs. 25, 26) Calomys Waterhouse, 1837. Proc. Zool. Soc. Lond., 1837:21. Hesperomys Waterhouse, 1839. Zoology Voy. "Bea- gle," 2:75. Type Species— Mus (Calomys) bimaculatus (Waterhouse), 1837, by original designation. Included Species— The specific taxonomy of Calomys is less stable than the other phyllotine genera. Species have undergone numerous reas- sessments in recent years, principally due to the input of karyotypic data. The nomenclature used in the phylogenetic analysis largely followed Hershkovitz (1962), and nomenclatural uncer- tainties of certain specimens are indicated in the Appendix. In her unpublished revision of the ge- nus, Olds (1988) recognized 10 species: bimacu- latus Waterhouse, 1837, callosus Rengger, 1830, hummelincki Husson, 1960, laucha Olfers, 1818, lepidus Thomas, 1884, murillus Thomas, 1916, musculinus Thomas, 1913, sorellus Thomas, 1 900, tener Winge, 1888, and venustus Thomas, 1894. Vitullo et al. ( 1 990) did not recognize bimaculatus, murillus, or tener but did recognize fecundus Thomas, 1926, and callidus Thomas, 1916. In contrast to Olds (1988), Musser and Carleton (1993) recognized nine species, among them cal- lidus. They treated fecundus as a subjective syn- onym of boliviae Thomas, 1901, and synonymized bimaculatus and murillus with laucha and mus- culinus, respectively. Whatever their rank, these taxa are properly included in Calomys, with res- ervations regarding sorellus as discussed under Comments. Diagnosis— Members of the tribe Phyllotini de- scended from a common ancestor with the follow- ing traits: no reduction in the mesoflexus M3 rel- ative to M2 (24), posterior margin of zygomatic plate anterior to M 1 (42), mesopterygoid fossa ly- ing more than 1 tooth-length posterior to M3 (70), and length of distal baculum 63-77% of proximal length (93). Distribution— From central Peru at high ele- vations, through Bolivia, northern and central Ar- 72 FIELDIANA: ZOOLOGY Fig. 25. Cranium and mandible of Calomys laucha (fnmh 23405). Scale bar = 10 mm. STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 73 Fig. 26. Upper and lower molars of Calomys laucha (fmnh 29246). gentina, far northern Chile, Paraguay, Uruguay, to southwestern and eastern Brazil. Calomys hum- melincki has a poorly known distribution in north- ern Venezuela, eastern Colombia, and several off- shore Caribbean islands. Comments— Phylogenetic relationships within Calomys are poorly known. Olds (1988) revised the genus and recognized five species-groups, two of which are monospecific, of unknown interre- lationship. Her groupings were based on tail length, diploid number, and multivariate size and shape of skulls. The five groups (with modal mammae counts) are as follows: callosus (10), venustus (10- 14), and tener (10); laucha (8), bimaculatus (10), and hummelincki (8); murillus (10-12) and mus- culinus ( 1 2-14); lepidus (8); and sorellus (8). These groupings bear little resemblance to the three rec- ognized by Vitullo et al. (1990) based on karyo- types. Group I is closely related to the ancestral type hypothesized by Pearson and Patton (1976) and includes sorellus (2N = 64, FN = 68), laucha (2N = 64, FN = 68), and hummelincki (2N = 60, FN = 64). Group II consists of a Robertsonian series from venustus (2N = 54-56, FN = 66) to fecundus (2N = 50, FN = 66), and callidus (2N = 48, FN = 66). Group III consists of callosus (2N = 36, FN = 48), lepidus (2N = 36, FN = 68), and musculinus (2N = 38, FN = 56). Number of ribs is consistent with Olds's scheme, as specimens as- signed by her to callosus, venustus, and tener all share the derived condition of 1 2 ribs and seven lumbar vertebrae. Calomys laucha and lepidus have the primitive 13 ribs and six lumbar vertebrae. This observation contradicts the statement that "C callosus, C. laucha, and C. lepidus generally [have] ... 1 3 thoracic, with 1 3 pairs of ribs, 6-7 lumbar" (Olds, 1988, p. 50). Many of the same specimens were examined in both studies. This observation also contradicts the coding by Carle- ton (1980), who coded callosus as having 13 ribs. Nineteen of the 20 skeletons of callosus examined in this study clearly had only 1 2 ribs, and one had a thin, short thirteenth pair that did not articulate with the twelfth thoracic vertebra. 74 FIELDIANA: ZOOLOGY The most-parsimonious trees from the phylo- genetic analysis (Figs. 22, 23; Steppan, 1993) in- dicate that sorellus is not a member of a Calomys clade but may instead be the sister taxon to all other phyllotines. The analysis above is equivocal, but the hypothesis that sorellus shares a more re- cent ancestor with other phyllotines than it does with Calomys is supported by the presence of a ventral pair of preputials (97), more than 25 caudal vertebrae (80), loss of the parastyle/anteroflexus Ml (12), a long interparietal (56), and two roots on m3 (9). Necromys Ameghino (1889) was synonymized with C. callosus by Hershkovitz (1962), but the type specimen was considered a senior synonym of Bolomys by Massoia and Pardifias (1993). Graomys Group Included Taxa— Eligmodontia and Graomys. Diagnosis— Members of the tribe Phyllotini de- scended from a common ancestor with the follow- ing traits: no reduction in the mesoflexus of M3 relative to M2 (24), hypoflexus of M3 intact, not pinched to form lake (26), premaxillaries pro- duced well anterior to incisors (37), supraorbital region posteriorly divergent (49), supraorbital edg- es ridged, overhanging (except Eligmodontia) (50), maxillary tooth rows parallel (except Eligmodon- tia) (74), squamosal fenestra present between mas- ticatory-buccinator trough and squamosal-ali- sphenoid groove (77), alisphenoid strut present (78), and tail dorsum sparsely furred (except G. pearsoni) (90). Comments— This generic group may well in- clude Phyllotis amicus and P. gerbillus, but as the current analysis cannot confidently resolve the is- sue, I prefer not to make formal nomenclatural changes. Should further studies confirm the inclu- sion of amicus and gerbillus, then they should be included in the Graomys group as well. Eligmodontia F. Cuvier (Figs. 27, 28) Included Species— At least three species have been demonstrated from karyotypic data: typus, puerulus Philippi, 1 896, and morgani Allen, 1 90 1 . Diagnosis— Members of the Graomys group descended from a common ancestor with the fol- lowing traits: hyper-opisthodont upper incisors (2), anterolabial cingulum ml indistinct ( 1 4), posterior shift of hypoflexid m3 relative to m2 (30), knob of anterior masseteric ridge exceeds dorsal edge of diastema (35), supraorbital edges angled (50), eu- stachian tubes do not reach posterior edge of pter- ygoid processes (63), parapterygoid fossa 1.5-2.5 times mesopterygoid fossa width (64), maxillary tooth rows posteriorly convergent (74), deltoid tu- berosity greater than 59% of humerus length from condyle (84), ventral surface of claws forming dis- tinct keel (85), Dl and D5 of pes subequal in length (86), sole of pes furred (88), *hind feet elongated, hypothenar pad absent, *fused plantar pads D2- 4, and hair in pectoral region entirely white from base to tip. Distribution— Found throughout southern Ar- gentina, far eastern Chile in the south, along the eastern slopes of the Andes in western and north- ern Argentina, and in the altiplano of northern Chile, southwestern Bolivia, and extreme southern Peru. Comments— Three species are now recognized, based mostly on karyotypes: typus, puerulus, and morgani. The specimens examined from Neuquen Province in western Argentina and from southern Chile are tentatively referred to the species mor- gani, the name offered by Kelt et al. (1991) for specimens with a karyotype of 2N = 32-33, FN = 32. Kelt et al. (1991) and Ortells et al. (1989) also recognize two other species of Eligmodontia: puerulus (2N = 50, FN = 48) from Bolivia, Peru, and northern Chile and typus (2N = 43—44, FN = 44) from central and eastern Argentina. Zambelli et al. ( 1 992) found typus to be sympatric with mor- gani at two localities in Neuquen Province near where some of the specimens examined in this study were collected. The recent chromosomal studies do not include morphological data that would allow more confident species assignments for the specimens examined in this study. Eligmodontia F. Cuvier, 1837. Ann. Sci. Nat. (Paris), ser. 2, 7:168. Eligmodon Wagner, 1841. Arch. Naturg., 1:125. Heligmodontia Agasiz 1 846. Nomencl. Zool. Mamm., Addenda, 5:136, 175. Type Species— Eligmodontia typus Cuvier, 1 837, by original designation. Graomys Thomas (Figs. 28, 29) Graomys Thomas, 1916. Ann. Mag. Nat. Hist., ser. 8, 17:141. Andalgalomys Williams and Mares, 1978. Ann. Car- negie Mus., 47:197. STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 75 Fig. 27. Cranium and mandible of Eligmodontia morgani (fmnh 133070). 76 FIELDIANA: ZOOLOGY ■A STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 77 Fig. 29. Cranium and mandible of Graomys griseoflavus (fmnh 28423). 78 FIELDIANA: ZOOLOGY Type Species— Mus (Phyllotis) griseo-flavus Waterhouse, 1837, by original designation. Included Species— Includes griseoflavus (Wa- terhouse, 1837), domorum (Thomas, 1902), olrogi (Williams & Mares, 1978), and pearsoni Myers, 1977. The status of the geographically restricted edithae Thomas, 1 9 1 9, is less clear, and specimens were not examined. Diagnosis— Members of the Graomys group descended from a common ancestor with the fol- lowing traits: distinct and large anterolabial cin- gulumml (14, 15), noshiftofmesoflexid m3 (29), moderately developed zygomatic spine, anterior border of zygomatic plate concave (43), supraor- bital sharply ridged, overhanging (50), *laterally apressed stapedial spine (59), *orbital wings of the presphenoid posterior from maximum constric- tion (69), maxillary tooth rows parallel (74), 12 thoracic and seven lumbar vertebrae (79), and moderately sized distal baculum (93). Distribution— Found at moderate to low ele- vations in southern Bolivia, western Paraguay, and northern and central Argentina, and reported from southwestern Brazil. Comments— Synonymy of A ndalgalomys is re- quired by the strong support for G. (Andalgalo- mys) pearsoni and G. griseoflavus sharing a com- mon ancestor more recently than either does with G. domorum. Phyllotis Waterhouse (Figs. 30, 31) Phyllotis Waterhouse, 1837. Proc. Zool. Soc. Lond., 1837:27. Paralomys Thomas, 1926. Ann. Mag. Nat. Hist., ser. 9, 17:315. Type Species: Mus darwini (Waterhouse), 1837, by subsequent designation (Thomas, 1 884, p. 449). Included Species: Minimally, Phyllotis sensu stricto includes caprinus Pearson, 1958, chilensis Mann, 1 945, definitus Osgood, 1915, darwini (Wa- terhouse, 1837), haggardi Thomas, 1898, magister Thomas, 1912, osgoodi Mann, 1945, osilaei. A. Allen, 1 90 1 , and xanthopygus (Waterhouse, 1837). Additional species included pending further re- visionary studies (see Comments): andium Tho- mas, 1912, wolffsohni Thomas, 1 902, amicus Tho- mas, 1900, and gerbillus Thomas, 1900. Musser and Carleton (1993) also recognized bonariensis Crespo, 1 964, which along with osgoodi was not examined for the cladistic analyses. Diagnosis— See discussion under Comments. Distribution— As currently defined, the genus is distributed throughout nonforest habitats in the Andes from Ecuador to the Straits of Magellan, from near sea level along the Pacific coast, to the altiplano. Comments— Woodman (1993) has recently rec- ommended that species names for all genera end- ing in the feminine -otis and derived from the Greek oroa, for ear, should be feminized. Four species of Phyllotis would be affected by this no- menclatural change: arnica from amicus, caprina from caprinus, definita from definitus, and xan- thopyga from xanthopygus. However, Pritchard (1994) argued that mammalian generic names ending in -otis are actually Latin derivations of the Greek, and Latin words ending in -is are of the 3rd declension and may be masculine, femi- nine, or neuter, depending on priority of usage when grouped with specific names. The first usage of Phyllotis with a specific epithet requiring gender agreement was with the masculine xanthopygus (Waterhouse, 1837). At issue is whether the -otis ending was a proper feminine form of otoo or was a latinization of the Greek. The Greek otis (otict) means bustard and, while feminine, refers to a bird that lacks external pinnae, and thus may not have originally been derived from "feminine-eared creature," a literal translation. It certainly serves as a poor reference for names relating to modifi- cations of ears. I retain the historical usage for Phyllotis species names, but proper resolution may await further investigation of the etymology of the original Greek forms. My analysis of morphological characters strong- ly indicates that Phyllotis is either polyphyletic or paraphyletic, but no single alternative hypothesis exists with which to confidently revise existing tax- onomy. Therefore, the genus is left unrevised and undiagnosed. It seems likely that amicus and ger- billus should be removed; the name Paralomys Thomas, 1926, is available for a genus including gerbillus. In fact, Braun ( 1 993) recently placed them in Paralomys, although her analysis indicates that it is paraphyletic. Should amicus and gerbillus not form a monophyletic group, then Paralomys would apply only to gerbillus. Phyllotis andium falls out- side the main Phyllotis clade and may well be a basal member that requires generic status in order to maintain a strictly monophyletic Phyllotis. The more highly derived wolffsohni seems to be a basal member of the clade including Auliscomys, An- dinomys, and Reithrodon. After excluding these four species, nine remain to form a monophyletic STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 79 Fig. 30. Cranium (fmnh 22325) and mandible (fmnh 22328) of Phyllotis darwini. 80 FIELDIANA: ZOOLOGY 5 o c ! 4 >> 5 a D STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 81 group in the most-parsimonious tree: caprinus, chilensis, darwini, definitus, haggardi, magister, osgoodi, osilae, and xanthopygus. Though not in- cluded in the cladistic analysis, chilensis and os- goodi are clearly members of Phyllot is sensu stric- to, virtually identical to xanthopygus rupestris for the characters used in the cladistic analysis. This study follows the recommendation of Walker et al. (1984) to restrict the specific name darwini to coastal Chilean populations and to in- clude the north Andean subspecies (e.g., rupestris) within xanthopygus. Musser and Carleton (1993) cited Walker et al. (1984) in aligning the north Andean subspecies under darwini and restricted xanthopygus to the south Andean subspecies (e.g., vaccarum), but Walker et al. (1984) were quite clear about the restriction of darwini to coastal Chilean populations. The specimens referred to darwini in Braun (1993) were instead xanthopy- gus. My recognition of chilensis as a distinct species differs from all recent treatments (Hershkovitz, 1962; Mann, 1978; Pearson, 1958). Unpublished morphometric, anatomical, and molecular data collected by me indicate the specific separation of chilensis from P. x. rupestris in southern Peru. The two taxa form clearly bimodal clusters in principal component space with little overlap. Where good series exist along transects, the transition between the taxa is sharp, identifiable to within a kilometer. Morphological intermediates (outliers) are not as- sociated with proximity to the transition zone. Phyllotis chilensis is autapomorphic in being the only phyllotine examined with three pairs of pre- putial glands. Additionally, Peruvian rupestris possesses the narrowest upper incisors in relation to incisor depth of any Phyllotis. Spotorno and Walker (1983) also found that chilensis was elec- trophoretically more closely related to darwini than to populations of true xanthopygus. It is not en- tirely clear whether chilensis or rupestris shows evidence of introgression with the other subspecies of xanthopygus, but current DNA sequence and revisionary studies should resolve the question. Loxodontomys Osgood (Figs. 31, 32) Loxodontomys Osgood, 1947. J. Mamm., 28:172. Type Species— Mus micropus Waterhouse, 1 837, by original designation and monotypy. Included Species— Includes the single species micropus. Distribution— Southern Andes of Chile and Argentina from about 36°S to the Straits of Ma- gellan. Diagnosis— Members of the tribe Phyllotini and allied to the Reithrodon group, descended from a common ancestor with the following traits: un- grooved upper incisors (1), tripartite dentine lake in the upper incisors (3), two labial roots Ml (5), two roots M3 (6), labial root ml present (7), two roots m2 (8), indistinct parastyle/anteroflexus M 1 (12), anterolabial cingulum distinct (14), proto- flexid m2 present as groove (22), hypoflexus M3 reduced relative to M2 (23), mesoflexid m3 re- duced and shifted anteriorly relative to m2 (28, 29), length of M3 greater than 20% alveolar length of tooth row (32), posterior border of mandibular symphysis sharply angled (36), premaxillaries ter- minating at or slightly anterior to incisive plane (37), incisive foramina terminating at level of paracone and protocone (38), antorbital bridge Vs- l A below dorsal surface of rostrum (41), nasals broader than interorbital constriction (48), supra- orbital edges angled for Vi of length (50), supra- orbital ridges and knobs absent (51, 52), internal carotid bounded by both auditory bulla and oc- cipital (62), mesopterygoid fossa distinctly nar- rower than parapterygoid fossa (64), posterior width of parapterygoid less than 1.5 times anterior width (65), parapterygoid fossa recessed slightly above palate (67), maxillary tooth rows posteriorly, divergent (74), sphenopalatine foramen absent or nearly ossified (75), squamosal fenestra present between squamosal groove and masticatory-buc- cinator trough (77), tail sparsely furred (90), pec- toral streaks present (92), and distal baculum less than 63% length of proximal baculum (93). Comments— Osgood (1947) described Loxo- dontomys as a subgenus of Phyllotis, and Braun ( 1 993) elevated it to a genus for micropus. Generic status was supported by Steppan (1993). Inclusion within Auliscomys is strongly argued against by this study, but karyotypic data would seem to sug- gest a close association (Walker & Spotorno, 1992). However, the karyotypic analysis assumed rather than tested a monophyletic Auliscomys sensu lato by not including outgroups in the analysis. The basal position of Loxodontomys relative to the divergence of the Auliscomys and Reithrodon groups allows the possibility that Loxodontomys and Auliscomys have retained relatively primitive karyotypes. Simonetti and Spotorno (1980) moved micropus from Phyllotis to Auliscomys because of its similar karyotype and proximity to Auliscomys species in an ordination analysis. The karyotypes 82 FIELDIANA: ZOOLOGY Fig. 32. Cranium and mandible of Loxodontomys micropus (fmnh 23287). STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 83 are indeed similar, but the multivariate analysis was based on only 4 external and 1 1 partially re- dundant molar measurements. Additionally, mi- cropus was compared XoAuliscomys, Phyllotis, and Andinomys, but to none of those taxa that this analysis indicates that it is related to. Their mul- tivariate analysis does not conflict with the results of this study. Osgood (1943) had included micropus in Aulis- comys, a subgenus of Phyllotis, but only supported this alignment by the development of the parastyle M2 (which he described as variable among groups allied to Phyllotis) and the "somewhat more oblique pattern" (Osgood, 1 943, p. 2 1 3) of the molar lophs. Otherwise, he found micropus "somewhat anom- alous" in association with Auliscomys. Pine et al. (1979) proposed that Loxodontomys Osgood was technically a nomen nudum because in Osgood's description, "it" referred to micropus rather than to Loxodontomys. However, in defin- ing Loxodontomys as a monotypic taxon, "it" re- ferred to both the species and subgenus, and "it" was compared to other genus-level taxa, not to individual species. Auliscomys Group Included Taxa— Auliscomys and Galenomys. Diagnosis— Members of the tribe Phyllotini al- lied to Chinchillula, Loxodontomys, and the An- dinomys and Reithrodon groups, descended from a common ancestor with the following traits: curved dentine lake in the upper incisors (3), length of M3 greater than 20% alveolar length of tooth row (32), capsular projection of mandible indistinct or absent (33), medioventral process of mandibular ramus absent, the ramus not sharply angled (36), premaxillaries terminating behind the incisive plane (37), *zygomatic spine absent, zygomatic plate convex and receding dorsally (43), zygomatic plate inclined less than 20° (44), posterior terminus of premaxillaries anterior to nasals (47), nasals broader than interorbital constriction (48), meso- pterygoid fossa distinctly narrower than parapter- ygoid fossa (64), and tails usually densely furred (90) and short to very short, always less than head and body length. Type Species— Reithrodon pictus Thomas, 1 884, by original designation. Included species— pictus (Thomas, 1884), bo- liviensis (Waterhouse, 1 846), and sublimis (Thom- as, 1900). Diagnosis— Members of the Auliscomys group descended from a common ancestor with the fol- lowing traits: upper incisors with shallow grooves or striae in most specimens (1), incisors orthodont (2), small labial root of M 1 , set medially (4), pos- terolophid ml distinct at all ages (19), procingul- um M2 moderately to well developed (21), highly reduced mesoflexid on m3 (28), posterior shift of hypoflexid on m3 (30), supraorbital region ante- riorly divergent, narrowest point posterior (except pictus) (49), interparietal/parietal length between 0.33 and 0.45 (56), internal carotid canal bounded by both auditory bulla and occipital (62), and max- illary tooth rows parallel (74). Distribution— Altiplano from central Peru to southwestern Bolivia and far northern Argentina and Chile. Comments— Braun (1993) erected Maresomys to contain boliviensis primarily because it was less similar to sublimis and pictus than they were to each other and because her cladistic analysis placed it as the sister-species to Galenomys garleppi. No putative synapomorphies for this topology or es- timates of confidence were reported. My study does not support sister taxon status between boliviensis and Galenomys but, instead, strongly supports a monophyletic Auliscomys (84% of bootstrap rep- licates, hypothesized synapomorphies in diagno- sis). Phenetic analyses in Braun (1993) and Spo- torno (1986) indicate that dissimilarities among boliviensis, sublimis, and pictus are comparable to that seen within Calomys and Phyllotis. The cur- rent taxonomy in regard to boliviensis, sublimis, and pictus appears to fully satisfy the objectives of both cladistic and phenetic concepts of system- atics. The species micropus is removed to Loxodon- tomys (see Comments therein). Galenomys Thomas (Figs. 34, 35) Auliscomys Osgood (Figs 33, 34) Auliscomys Osgood, 1915. Field Mus. Nat. Hist. Publ. Zool. Ser., 10:190. Maresomys Braun , 1993:40. Galenomys Thomas, 1916. Ann. Mag. Nat. Hist., ser. 8, 17:143. Type Species— Phyllotis garleppi Thomas, 1 898, by original designation. Included Species— Includes the single species garleppi (Thomas, 1916). 84 FIELDIANA: ZOOLOGY Fig. 33. Cranium and mandible of Auliscomys pictus (fmnh 64344). STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 85 a D 86 FIELDIANA: ZOOLOGY Fig. 35. Cranium (amnh 246947) and mandible (fmnh 53845) of Galenomys garleppi. STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 87 Diagnosis— Member of the Auliscomys group descended from a common ancestor with the fol- lowing traits: incisors orthodont (2); lower incisors highly procumbent; three roots on m3 (9); distinct anteromedian flexus on Ml (10); reduced hypo- flexus on M3 (24); highly reduced mesoflexid on m3 (28); knob of anterior masseteric ridge reaches dorsal edge of mandible (35); *skull strongly arched upward in region of supraorbital to rostrum, ros- trum flexed downward; internal carotid canal bounded by both auditory bulla and occipital (62); maxillary tooth rows posteriorly convergent (74), *outwardly bowed; no fenestra where masticato- ry-buccinator nerve passes over squamosal-ali- sphenoid groove (77); deltoid tuberosity greater than 59% along humerus from the condyle (84); soles of hindfeet furred (88); tail densely furred (90); and *tail very short, less than 40% head and body length. Distribution— Restricted distribution in the provinces or departments of Puno in Peru, La Paz and Oruro in Bolivia, and Tarapaca in Chile. Comments— Braun (1993) erected Maresomys for boliviensis based on its sister-group status with Galenomys, creating an otherwise paraphyletic Auliscomys. The strength of a Galenomys/ Mare- somys clade relative to other topologies cannot be evaluated because no synapomorphies are report- ed. This study indicates robust support for a monophyletic Auliscomys, to which Galenomys is the sister-group. Chinchillula Thomas (Figs. 36, 37) ChinchillulaThomas, 1898. Ann. Mag. Nat. Hist., ser. 7, 1:280. Type Species— Chinchillula sahamae Thomas, 1898, by original designation. Included Species— Includes the single species sahamae. Diagnosis— Member of the tribe Phyllotini and allied to the Auliscomys and Andinomys generic groups, descended from a common ancestor with the following traits: characterized by *very large body size; curved fissures in upper incisors (3); one root on M3 (6); *lingual root of M2 absent; three roots on m2 (8); small mesostyles present (11); opposing flexi on Ml do not overlap (13); posterolophid ml absent (19); procingulum M2 absent (21); length of M3 less than 0.205 times the length of the molar tooth row (32); zygomatic plate rounded, spine absent (43); anterior root of zy- gomata inserting near dorsal surface of rostrum (41); supraorbital ridges raised dorsally (51); fron- toparietal suture straight, forming a right or acute angle (54, 55); postglenoid foramen anterior to subsquamosal foramen (61); internal carotid not bounded by basioccipital (62); anterior border of mesopterygoid fossa lying between and 0.33 tooth-length behind M3s (70); ventral surface of claws on manus fused, forming distinct keel (85); highly distinctive coloration, with white hip patches contrasting with dark brown to black side patches, tawny over dark gray back, and white postauricular patches. Distribution— Altiplano of southern Peru, far western Bolivia, and far northern Chile. Comments— I regard Chinchillula as Phyllotini sedis mutabilis to reflect the uncertainty as to the two near equally parsimonious positions it can occupy: the basal member of the Auliscomys group or the basal member of the A ndinomys group. Nei- ther topology is strongly supported, but Chinchil- lula's basal position near the divergence of these two groups seems highly likely. Andinomys Group Included Taxa— Andinomys and Irenomys. Diagnosis— Members of the tribe Phyllotini and allied to the Auliscomys and Reithrodon generic groups, descended from a common ancestor with the following traits: fissure of upper incisor curved or tripartite (3); labial root M 1 small or absent (4); two roots m2 (8); well-developed procingulum m2 (22); no reduction hypoflexus M3 (23); length of M3 greater than 25% alveolar length of tooth row (32); anterior masseteric ridge well ventral and posterior to dip in diastema (35); posterior border of mandibular ramus sharply angled (36); pre- maxillaries at or slightly anterior to incisive plane (37); separation of anterior apexes of incisive fo- ramina greater than 80% that of posterior apexes (40); nasals broader than interorbital constriction (48); incomplete fusion or vascularization of fron- tals (53); frontoparietal sutures straight, forming acute or right angle (54, 55); internal carotid not bounded by basioccipital (62); mesopterygoid fos- sa and parapterygoid fossa subequally broad (64); mesopterygoid fossa reaching M3s (70); posterior palatal pits located subequal or posterior to an- terior border of mesopterygoid fossa (73); and maxillary tooth rows posteriorly divergent (74). 88 FIELDIANA: ZOOLOGY Fig. 36. Cranium (fmnh 52479) and mandible (fmnh 52478) of Chinchillula sahamae. STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 89 n. 2 90 FIELDIANA: ZOOLOGY Andinomys Thomas (Figs. 37, 38) Andinomys Thomas, 1902. Proc. Zool. Soc. Lond., 1902(1):116. Type Species— Andinomys edax Thomas, 1 902, by original designation. Included Species— Includes the single species edax. Diagnosis— Members of the Andinomys group descended from a common ancestor with the fol- lowing traits: molars opisthodont (2); labial root of Ml present, small, set medially (4); primary cusps alternate (16); lophs sharply angled; anter- omedian Ilex id m 1 prominent ( 1 7); mesoflexid m3 highly reduced (28); moderate zygomatic spine, anterior border of zygomatic plate weakly concave (43); supraorbital region anteriorly divergent (49); supraorbital swellings present (52); *fontanelle formed by incomplete fusion of frontals (53); post- glenoid foramen anterior to subsquamosal fora- men (6 1 ); eustachian tubes extend anteriad to base of pterygoid processes (63); parapterygoid recessed slightly above level of bony palate (67); second cervical neural spine enlarged into "plow"-shaped, distinct keel (82); hypothenar pad intermediate to first interdigital and thenar pads (87); and tail bi- colored and densely furred (89, 90). Distribution— Found in the highlands of southern Peru, far northern Chile, southwestern Bolivia, and northern Argentina. Comments— Previously, I had treated northern and southern populations of A. edax edax as sep- arate OTUs for the cladistic analysis (Steppan, 1993) because of geographic differentiation for qualitative characters. Subsequent examination of additional material has indicated that, although the variation is significant, it is also complex, and the recognition of separate taxa would be pre- mature until a thorough generic revision has been conducted. Irenomys Thomas (Figs. 39, 40) Irenomys Thomas, 1919. Ann. Mag. Nat. Hist., ser. 9, 3:201. Type Species— Reithrodon longicaudatus Phi- lippi, 1900, by original designation. Included Species— Irenomys tarsalis (Philippi, 1900). Diagnosis— Members of the Andinomys group descended from a common ancestor with the fol- lowing traits: incisors deeply grooved (1); labial root Ml absent (4); three roots on M3 (6); labial root of ml absent (7); "opposing flexi/flexids of all molars meet at midline, nearly severing mures/ murids (13); cusps opposite (16); posterolophid of ml absent (19); procingulum of M2 absent (21); height of the coronoid process subequal with man- dibular condyle (34); incisive foramina extending to protocone (38); hamular process of the squa- mosal reduced in thickness along entire length (60); medial process of the posterior palate absent (71); alisphenoid strut present as a consistent dorsal process that does not cross the foramen ovale (78); more than 30 caudal vertebrae (80); deltoid tu- berosity greater than 59% of the length of the hu- merus measured from the condyle (84); heels of the pes only sparsely furred (88); and tail mono- colored (89). Distribution— Low to moderate elevations from Nuble Province in south central Chile to the Straits of Magellan; Chiloe Island and Guaitecas Islands. Comments— Characters, distribution, and ecol- ogy reviewed by Kelt (1993). Reithrodon Group Included Taxa— Includes the highly differen- tiated genera Euneomys, Neotomys, and Reithro- don. This group was first formally identified by Olds and Anderson (1989). Diagnosis— Members of the tribe Phyllotini al- lied to Loxodontomys and the Auliscomys and An- dinomys groups, descended from a common an- cestor with the following traits: distinct grooves on the upper incisors (1); tripartite dentine lake in the upper incisors (3); *sigmoidal molars; three roots on M3 (6); no labial root on m 1 (7); indistinct or weakly developed anterolabial cingulum ml (14); procingulum on m2 absent (22); no reduction or shift of m3 mesoflexid (28, 29); length of M3 greater than 20% alveolar length of tooth row (32); height of the coronoid process subequal with the mandibular condyle (34); posterior border of man- dibular symphysis sharply angled or with distinct process (36); strong zygomatic plate; anterior root of zygomata inserting near or on dorsal surface of rostrum (41); *premaxillo-maxillary suture with acutely angled bend, so that it lies nearly horizon- tal as it passes under ventral surface of rostrum (45); interorbital region narrow; supraorbital STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 91 Fig. 38. Cranium (fmnh 29157) and mandible (fmnh 23435) of Andinomys edax. 92 FIELDIANA: ZOOLOGY Fig. 39. Cranium and mandible of Irenomys tarsalis (fmnh 133164). STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 93 I 1 s: a 94 FIELDIANA: ZOOLOGY ridges raised dorsally (51); supraorbital swellings present (52); temporal vacuities positioned anter- odorsally (61); mesopterygoid fossa distinctly nar- rower than parapterygoid fossa (64); posterior width parapterygoid less than 1.5 times anterior width (65); medium to deep parapterygoid fossa (67); maxillary tooth rows posteriorly divergent (74); and fewer than 25 caudal vertebrae (80). Euneomys Coues (Figs. 40, 41) Euneomys Coues, 1874. Proc. Acad. Nat. Sci. Phila- delphia, 26:185. IBothriomys Ameghino, 1889. Act. Acad. Nat. Cienc. Rep. Argentina, 6:1 18. Chelemyscus Thomas, 1925. Ann. Mag. Nat. Hist., ser. 9, 15:584-585. Type Species— Reithrodon chinchilloides Wa- terhouse, 1839, by original designation. Included Species— Includes Euneomys chin- chilloides (Waterhouse, 1839), E. mordax Thom- as, 1 9 1 2, and E. petersoni J. A. Allen, 1 903. Status of the fossil Bothriomys catenatus (Ameghino, 1889) is uncertain (see Comments). Diagnosis— Members of the Reithrodon group descended from a common ancestor with the fol- lowing traits: anterior incisor grooves (1); antero- labial cingulum absent (14); *procingulum sepa- rated from anterior murid in ml by fusion of metaflexid and protoflexid (18); posteroflexid in m3 present as shallow groove in juveniles, absent in adults (20); anteroflexus M2 shallow (21); hy- poflexus pinched off to form dentine lake in M3 (26); *dorsal surface of zygomatic plate rising above dorsal surface of rostrum, anterior root of zygo- mata inserting at dorsal surface (41); zygomatic plate inclined less than 20° from vertical (44); ali- sphenoid strut present (78); *highly elongated neu- ral spine of third thoracic vertebra (81); and spine of second cervical vertebra overlaps third cervical vertebra (83). Distribution— Andes from central Chile and Argentina to Tierra del Fuego. Comments— Hershkovitz (1962) lists Bothrio- mys, the type of which is the Pleistocene mandible designated catenatus (Ameghino, 1889), as a syn- onym of Euneomys. While the specimen does share with Eunomys the number and depth of the loph- ids, as well as the diagnostic separation of the pro- cingulum on m 1 , the angles of the labial lophids and the triangular shape of the procingulum are very different from those found in extant Euneo- mys. The triangular shape of the procingulum is most similar to that found in Reithrodon and to a lesser extent Neotomys. Likewise, the obtuse ori- entation of the opposing lophids resembles Reith- rodon and Neotomys more than the parallel lo- phids in Euneomys. In fact, Pardinas (in press) reports that the type of Bothriomys is an immature individual, and synonymizes it with Graomys. Pearson and Christie (1991) provided compel- ling morphologic evidence for specific distinction between chinchilloides and mordax, fully consis- tent with data from karyotypes and ordination of morphometric data (Reise & Gallardo, 1990). Chelemyscus is based on a mismatched skin and skeleton whose associated locality is also suspect (Hershkovitz, 1962; Pearson & Christie, 1991). The skull is the type of fossor, but it is unclear at this time to which species of Euneomys it belongs (Pearson & Christie, 1991). Musser and Carleton (1 993) recognized petersoni as a species, in contrast to Hershkovitz (1962), Reise and Gallardo (1990), and Pearson and Christie (1991). However, Reise and Gallardo's (1 990) results show petersoni to be largely distinct from chinchilloides in multivariate analyses, with some minimal overlap. Musser and Carleton (1993) correctly call for a rigorous revi- sion. Neotomys Thomas (Figs. 42, 43) Neotomys Thomas, 1894. Ann. Mag. Nat. Hist., ser. 6, 14:346. Type Species— Neotomys ebriosus Thomas, 1894, by original designation. Included Species— Includes the single species ebriosus. Diagnosis— Members of the Reithrodon group descended from a common ancestor with the fol- lowing traits: *anterior surface of upper incisors slightly concave; *upper incisor grooves forming distinctly pinched fold on lateral margin (1); lower incisors steeply angled; three roots on lower m2 (8); three roots on m3 (9); primary cusps alternate (16); anteromedian flexid lost (17); reduction of mesoflexid in m3 (28); very large M3s, greater than 'A tooth row length (32); *mandible very deep and robust; indistinct capsular projection of the man- dible (33); coronoid process below level of man- dibular condyle (34); *distinct ventromedial pro- cess of mandibular ramus (36); premaxillaries protruded well anterior of incisive plane (37); *in- STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 95 Fig. 41. Cranium and mandible of Euneomys chinchilloides (fmnh 133088). 96 FIELDIANA: ZOOLOGY Fig. 42. Cranium and mandible of Neotomys ebriosus (fmnh 107842). STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 97 98 FIELDIANA: ZOOLOGY Fig. 44. Cranium and mandible of Reithrodon auritus (fmnh 134225). STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 99 cisive foramina not reaching anterior conules of Ml (38); anterior apexes of incisive foramina as broadly separated as posterior apexes (40); well- developed zygomatic spine (43); supraorbital ridg- es weak (51); frontals incompletely fused or vas- cularized (53); interparietal/parietal length be- tween 0.33 and 0.45 (56); eustachian tubes extend past base of pterygoid processes (63); paraptery- goid deeply excavated (67); mesopterygoid fossa reaches M3s (70); distinct posterior palatine ridge (72); stapedial foramen present, sphenofrontal fo- ramen and squamosal-alisphenoid groove absent (76); alisphenoid strut absent (78); neural spine on second cervical vertebra enlarged into "plow"- shaped keel (82); tail bicolored and densely furred (89, 90); and pectoral streak present (92). Distribution— Altiplano and highlands of Peru, southwestern Bolivia, far northern Chile, to high- lands of northern Argentina. Reithrodon Waterhouse (Figs. 43, 44) Reithrodon Waterhouse, 1837. Proc. Zool. Soc. Lond., 1837:29. Ptyssophorus Ameghino, 1889. Act. Acad. Nat. Cienc. Rep. Argentina, PI. IV. Tretomys Ameghino, 1889. Act. Acad. Nat. Cienc. Rep. Argentina, PL IV. IProreithrodon Ameghino, 1908. Anal. Mus. Nac. Buenos Aires, 10:424. Type Species— Reithrodon typicus Waterhouse, 1837, by original designation. Included Species— Includes auritus (Fischer, 1814), and typicus Waterhouse, 1837. Diagnosis— Members of the Reithrodon group descended from a common ancestor with the fol- lowing traits: an additional shallow groove at mid- line of the upper incisors (1); upper incisors hyper- opisthodont (2); distinct, laterally positioned, la- bial root of Ml (4); *two lingual roots on M2; presence of a labial root in m 1 (7); three roots on m2 (8); primary cusps alternate (16); protoflexid present on m2 as short groove (22); *incisive fora- mina extending posterior to hypocone (38); *deep- ly excised zygomatic plate and long zygomatic spine (43); vaulted cranium; *tegmen tympani does not contact suspensory process of squamosal (58); ha- mular process of the squamosal reduced along en- tire length (60); internal carotid canal bounded by both auditory bulla and occipital (62); posterior width of mesopterygoid fossa greater than 2.5 times the anterior width (66); parapterygoids deeply ex- cavated (67); *optic foramen very large, orbital wings of the presphenoid filamentous (68); distinct posterior palatine ridge (72); *large sphenopalatine foramen (75); *stapedial foramen, sphenofrontal foramen, and squamosal-alisphenoid groove all absent (76); alisphenoid process present (78); 12 thoracic and 7 lumbar vertebrae (79); nuchal lig- ament sometimes attaches to third thoracic ver- tebra (81); and first and fifth digits of pes short and subequal in length (86). Distribution— Central and southern Argenti- na, southern Chile, Uruguay, and southernmost Brazil. Comments— At least 13 species-group names have been proposed for Reithrodon. Its system- atics have recently been reviewed by Ortells et al. (1988) in the context of new karyotype data. They recognized two species: typicus for the Uruguayan- Brazilian form with 2N = 28 and auritus Fischer, 1814 (= physodes Olfers, 1818) for the pampean and central Argentinean form with 2N = 34. The fossils described as Reithrodon chapalmalense Ameghino may not belong to Reithrodon. Based on the drawing in Roverto (1914), one anterior cranium lacks two diagnostic characters: the in- cisive foramina do not extend posterior to the an- terior conules, and the premaxillo-maxillary su- ture does not make an acute-angled bend (diagnostic of the generic group). These two traits cannot be assessed in the Pleistocene fossils at- tributed to Ptyssophorus (left mandible) and Tre- tomys (left upper molars and anterior root of zy- gomata), which otherwise appear referable to Reithrodon. Of 16 skeletons examined, one shows a longer neural spine on the third thoracic vertebra than on the second thoracic vertebra; this is the con- dition otherwise found only in Euneomys. Five other skeletons show spines on both T2 and T3 equally elongated, but no alcohol specimens were dissected to verify the insertion of the nuchal lig- ament, which in ichthyomyines is coincident with the elongated spine (Voss, 1988). The phallus of Reithrodon has been characterized by Hooper (1962). Additional taxonomic history can be found in Osgood (1943) and Tate (1932b). Acknowledgments Sincere thanks go to Bruce D. Patterson for his contributions in innumerable discussions, his time, and his expertise. Philip Hershkovitz shared many 100 FIELDIANA: ZOOLOGY insights into Neotropical mammals and was always available for discussions. Robert Voss generously examined specimens and added many insights. Thanks go to Sydney Anderson, James L. Patton, and Philip Myers for making specimens available for examination on loan, to Angel Spotorno, Jose Yanez, and Chris Carmichael for access to spec- imens in their care, and to Bill Stanley, Barbara Stein, Juan Carlos Torres-Mura, and Laura Abrac- zinskas for assisting with access to specimens. Bruce Patterson and Philip Hershkovitz provided help- ful comments on earlier drafts of the manuscript. Michael Carleton, Philip Myers, and three anon- ymous reviewers provided detailed comments that significantly improved the organization and con- tent of this manuscript. Barry Chernoff, John Flynn, Joel Brown, Jack Fooden, Lawrence Heaney, Ol- iver Pearson, and Angel Spotorno provided help- ful comments in discussions. I thank Betty Strack for her instruction and assistance with the scan- ning electron microscope. Volunteer Jessica G. Shull drew the illustrations in Figures 6-8, 10-12, 17, and 18. Vincent Ferguson printed the photo- graphs. A. Mayumi Kawamoto assisted with the figure preparation and drew the illustrations in Figures 9 and 15. Financial support was provided principally by the Rowley Graduate Fellowship of the Field Museum of Natural History and the Searle Fellowship of the University of Chicago, as well as by a Collections Study Grant from the Amer- ican Museum of Natural History, a Grant-in-Aid of Research from the National Academy of Sci- ences, through Sigma Xi, the Scientific Research Society, a Center for Latin American Studies Travel Grant, and a Grant-in-Aid of Research from the American Society of Mammalogists. The Marshall Field III Fund provided financial support for the acquisition of some of the specimens examined. Literature Cited Ameghino, F. 1889. 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John Wiley, New York, 439 pp. Williams, D. F., and M. A. Mares. 1978. A new genus and species of phyllotine rodent (Mammalia: Muridae) from northwestern Argentina. Annals of the Carnegie Museum, 47: 193-221. Woodman, N. 1993. The correct gender of mamma- lian generic names ending in -Otis. Journal of Mam- malogy, 74: 544-546. Zambelli, A., F. Dyzenchauz, A. Ramos, N. de Rosa, E. Wainberg, and O. A. Reig. 1 992. Cytogenetics and karyosystematics of phyllotine rodents (Criceti- dae, Sigmodontinae). III. New data on the distribution and variability of karyomorphs of the genus Elig- modontia. Zeitschrift fiir Saugetierkunde, 57: 155-162. Appendix: Specimens Examined Specimens are from the Field Museum of Nat- ural History unless otherwise designated. The ab- breviations skel(s) and phal(s) designate those specimens from which skeletons or phalli were examined. Tribe Phyllotini Calomys callosus— ARGENTINA. Catamarca: La Merced (msu 19235, 1 9237- skels). Jujuy: Cal- ilegua (22235 — skel, 23373; regarded as venustus by Olds, 1988). Tucuman: Conception (30167- 30173; regarded as venustus by Olds, 1988). BO- LIVIA. El Beni: San Juan (1 18807, 1 18808); San Joaquin (117123); Yuatre (118296); Yutiole (118605, 118610, 118294). Santa Cruz: San Mi- guel Rincon (amnh 260686-260690-skels). Tari- ja: Villa Montes (34238 -skel). PARAGUAY. Chaco: Fortin Madrejon, WNW (ummz 125466, 125468-125477— skels). Presidente Hayes: Juan de Zalazar, 8 km NE (ummz 133915-133922- skels). Total: 35. Calomys hummelincki— COLOMBIA. La Gua- jira: W Pto. Lopez, E Maicao (usnm 483982). VENEZUELA. Maru lab colony, originally from Monagas: 45 km S Maturin, close to Rio Tigre (usnm 460437^6044 1 , 460447). Monagas: 47 km SSE Maturin, Puente Tigre (usnm 388 104, 388 105, 388107, 3881 10, 3881 13). Total: 12. Calomys laucha— ARGENTINA. Buenos Ai- res: Dorrego (50939, 50940, 50942-50945; re- garded as murillus by Olds, 1 988); near Henderson (23395); Partida Balcarce (msu 16815, 16816, 16818, 168 19 -skels); Urdampilleta (23405; re- garded as murillus by Olds, 1988). Rio Negro: Chimpay (50932, 50937; regarded as murillus by 104 FIELDIANA: ZOOLOGY Olds, 1988). BOLIVIA. Tarija: Villa Montes, 10 km E (amnh 246668, 246674, 246841, 246849, 246867-skels). PARAGUAY. Presidente Hayes: Juan de Zalazar, 8 km NE (ummz 133928— skel). Total: 20. Calomys lepidus— BOLIVIA. La Paz: Ulla-ulla (ummz 121081— skel). PERU. Arequipa: Callalli, 15 km S (mvz 174019— skel); Laguna Salinas (49752-skel). Ayacucho: San Miguel (75419). Cuzco: Machu Picchu (107823— phal). Huancav- elica: Santa Ines (75420). Junin: Carhuamayo (54743). Puno: Hac. Collacachi (49555, 49749- skel, 51429). Total: 10. Calomys sorellus— PERU. Ancash: Hda. Catoc (81288, 81289); Nevado Quincayhuanca (81276, 8 1287). Arequipa: Arequipa (107795— phal); Car- aveli (107399-phal); Chivay (107688, 107689, 107732 — phals); Ayacucho: Chunyacc (ummz 120286 -skel); Jawaymachay (ummz 120291 — skel); Pacaicasu (ummz 120288, 120289 -skels); Tambo, San Miguel (75388, 75389); Tucumachay (ummz 120290— skel). Cuzco: Huancarani (mvz 171549-171554— skels). La Libertad: mountains near Otuzco (19209, 19210). Total: 24. Andalgalomys pearsoni— BOLIVIA. Santa Cruz: Robore, 29.5 km W (amnh 260762-skel). PAR- AGUAY. Nueva Asuncion: km 620, Trans-Chaco road (ummz, uncataloged [T. W. Nelson field num- bers 184, 193, 201, 202, 233]). Total: 6. Eligmodontia morgani— ARGENTINA. Neu- quen: Chos-Malal (29 1 53); Las Lajas (29 1 55). Rio Negro: Choele Choel (41293); Pilcaniyeu (29152). Santa Cruz: Piedra Clavada (35351). CHILE. Aisen: Chile Chico (133010, 133018, 133022, 133025-skels; 133027; 133068-skel); Coih- aique Alto (133005 -skel); Pto. Ibanez (133070). Magallanes: Lake Sarmiento (50582). Total: 14. Graomys domorum— BOLIVIA. Cochabamba: Aiquile (50961-50963); Parotani (21525, 21526); Pena Blanca (amnh 255966 — skel); Tin-Tin (50967-50969, 51920, 51921). Santa Cruz: Com- apara (amnh 260750-260754 — skels); Florida (72884). Total: 17. Graomys griseojlavus — ARGENTINA. Cata- marca: Belen (28423); Pta. Tinogasta (29163). Rio Negro: Chimpay (50920, 50923-50928). BOLIV- IA. Santa Cruz: Cordillera Guanacos (21431, 21432). Tarija: Tablada (29165, 29166); Tiquipa, Laguna Palmar (amnh 246777, 246778— skels); Villa Montes (amnh 246773, 246779 -skels). PARAGUAY. Boqueron: Colonia Fernheim (54359, 54360); La Urbana (34235). Alto Para- guay: Puerto Casado (54407). Total: 21. Phyllotis amicus— PERU. Arequipa: Caraveli, Atiquipa (107389— phal). La Libertad: Menocu- cho (19258-19263). Lima: Chos (107347, 107352-phals). Total: 9. Phyllotis andium— ECUADOR. Azuay: Valle de Yunguilla (43311). PERU. Ancash: Macate (20914, 20915, 20923, 20938, 21 145); Rio Mosna (129248, 129249 -skels). Libertad: Hac. Llagueda (19464). Lima: Lima (107361 -phal). Total: 10. Phyllotis caprinus— ARGENTINA. Jujuy: Mai- mara (85847); Sierra de Zenta, La Laguna (85848, 85849); Sierra de Zenta (41287). Total: 4. Phyllotis darwini— CHILE. Aconcagua: Papudo (22679-22684); Pte. Los Molles (119507- 1 19509— skels). Coquimbo: Parque Nac. Fray Jorge (133874, 133875, 133879-133881, 133894; 133896-skel); Romero (22325-22329). Santiago: Cerro Manquehue (119491-119497; 119500— skel). Valparaiso: Olmue (22346). Total: 30. Phyllotis definitus —PERU . Ancach: Macate (21126-21128— topotypes). Total: 3. Phyllotis gerbillus— PERU. Lambayeque: Lam- bayeque, 1 6 km NW (mvz 1 4 1 847); Morrope (mvz 138148, 138 149 -skels). Piura: Piura (21916, 81265-81273). Total: 13. Phyllotis haggardi— ECUADOR. Azuay: Con- trayerbas (amnh 61856— skel). Chimborazo: Mt. Chimborazo (53306-53308). Pichincha: Mt. Pi- chincha (443 1 1 , 443 1 3, 443 1 7, 53305, 920 1 2); Sa- loya (53309). Total: 10. Phyllotis magister— PERU . Arequipa: Arequipa (35360, 35361); Cailloma, Chivay (107690, 107691 —phals). Moquegua: Ilubaya, 3 km N To- rata (107417); Mariscal Nieto (107469 -phal). Tacna:Tarata (107561, 107611-107613, 107616, 107620, 107622-phal, 107623, 107625, 107629; mvz 143749). Total: 17. Phyllotis osilae— PERU. Puno: Chucuito (5 1285, 51287; 107843, 1078 59 -phals); Have, 35 km S (107860, 107870-107872, 107874, 107881, 107885, 107887, 107888, 107891, 107894- 107896); Pucara, 6 km S (mvz 173165); Santa Rosa, 12 km S (mvz 173162); Yunguyo (51269, 51270, 51274, 51278). Total: 23. Phyllotis wolffsohni— BOLIVIA. Chuquisaca: Padilla, 9 km N (amnh 263693, 2639 1 2, 2639 13- skels); Rio Limon (amnh 263914— skel). Cocha- bamba: Liriuni (140814); Pocona (461 13); Tapa- cari (mvz 1 20 1 80); Taquina (50957-50960, 51918, 51919). Santa Cruz: Comarapa, 21 km W (amnh 263914-skel). Total: 14. Phyllotis xanthopygus rupestris— BOLIVIA. La STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 105 Paz: Esperanza, Pacajes (53607, 53612). CHILE. Antofagasta: E of San Pedro (22303, 22304, 22307, 22308, 22311). Coquimbo: Paiguano (22251, 22271-22273, 22277, 22285). Tarapaca: Arica, 72 km E (133830, 133832, 133835, 133836). PERU. Arequipa: Yura (49744, 49763, 49766). Moque- gua: Torata (107405, 107407, 107415-phals). Tacna: Tarata (107617, 1 97642 -phals). Total: 26. Phyllotis xanthopygus xanthopygus— ARGEN- TINA. Santa Cruz: Rio Ecker (124384-124388, 124436-124439). CHILE. Aisen: Chile Chico (133940, 133943, 133944, 133947, 133958, 133973, 133979, 1 33982). Magallanes: Ultima Es- peranza, Laguna Lazo (50542). Total: 50. Loxodontomys micropus— ARGENTINA. Rio Negro: San Carlos de Bariloche (23840-23842). Santa Cruz: Rio Ecker ( 1 24393, 1 24394), ( 1 24397, 124435). CHILE. Aisen: Pto. Ibafiez (132705, 132706 — skels); Reserva Nac. Coihaique (132874-phal). Rio Nireguao (22229-skel; 23283-23285, 23287). Llanquihue (50647). Ma- gallanes: Pto. Natales (506 1 4); Pta. Arenas (506 1 5- 50622; 127337-phal). Malleco: Cerro Nahuel- buta (50643-50645). Osorno: Refugio, Valle de la Picada (127717-127720-skels). Total: 33. Auliscomys boliviensis— BOLIVIA. La Paz: Pa- cajes Province, Esperanza (53582, 53583, 53586, 53589-53599). CHILE. Tarapaca: Choquelimpie (22690, 22691). PERU. Arequipa: Cailloma (49765, 49768-49771, 49774-skels); Puno: Pas- to Grande, 30 mi W Mazo Cruz (mvz 114719); San Antonio de Esquilache (49574-49577, 49579- 49581). Total: 30. Auliscomys pictus— PERU. Arequipa: Cailloma (49775_skel; 107678, 107716-phals); Cuzco: Machu Picchu, 20 km E (107804-phal, 107806, 107819). Junin: Carhuamayo (54734-54742); Ju- nin (21132, 21133, 21 135-21 142- topotypes); Pachacayo (20060); Tarma (64344). Puno: Puno, Hac. Collacachi (49751— skel); Santa Rosa, 6 km W (107918, 107920, 107922, 107925-skel, 107926; 107968, 107975 -skels). Total: 34. Auliscomys sublimis— PERU. Arequipa: Cail- loma, Chivay (107696, 10771 1 -phals); Laguna Salinas (49542, 49543, 49546, 49547); Sumbay (49536, 49537, 49539, 49540, 49544, 49545). Puno: Yunguyo, 6 km S (51260); Huacullani (52669-52671); Have, 35 km S (107873); Laguna de Loriscota, 5 mi N (mvz 145613— skel); Puno (amnh 213596, 213597, 213601). Total: 20. Chinchillula sahamae— PERU . Arequipa: Cail- loma (49406, 49407 -skel, 49421, 49422); Sum- bay (49401, 49417, 49418). Cuzco: Cordillera de Sicuani (83475). Puno: Asillo, 3 mi W, Hac. Po- socani (51254, 51255); Picotani (52478-52482); Pto. Arturo (53156). Total: 16. Galenomys garleppi— BOLIVIA. La Paz: Pa- cajes Province, Esperanza (53845). Oruro: Eucal- iptus (amnh 24694 1-246947 -skels). Total: 8. Andinomys edax— ARGENTINA. Jujuy: W of Yala (23434, 23435); Tilcara (mvz 120222, 120223, 141617). BOLIVIA. Cochabamba: Ayopaca Prov- ince, El Choro (74869). Potosi: Potosi, 20 mi S (mvz 120224-120226); Yuruma (29156, 29157). Tarija: Camataqui, 25 mi SSE (mvz 120227- 120232). CHILE. Tarapaca: Arica, 72 km E (132647, 132648, 132651 -skels). PERU. Puno: Yunguyo, 6 km S (51279-51283). Tacna: Tarata, 1.5 mi N (mvz 139480, 139481). Total: 27. Irenomys tarsalis— CHILE. Aisen: La Junta (133164). Chiloe: Rio Inio (22528, 22529, 22531- 22535). Llanquihue: Peulla (50558, 50559-skels; 50563, 50588, 58589). Osorno: Osorno, 84 km SE (124056-124058); Osorno, 53 km SSE (133137, 133138, 133 142- skels); Osorno, 44 km SSE (133136, 133139, 133140); Osorno, 32 km SSE (133131, 133155-skel); Maicolpue, 65 km W Osorno (133 133, 133136, 1 331 39); Rufugio, Valle de la Picada (127732-skel). Total: 28. Euneomys chinchilloides— ARGENTINA. Ti- erra del Fuego: Lago Fagnano (50736). CHILE. Aisen: Pto. Ibafiez (133088, 133089-skels: 134027; 134181, 134182-skels; 134183, 134184, 1 34 1 86, 1 34233). Magallanes: Pta. Arenas (50600, 50601). Total: 12. Euneomys petersoni — CHILE. Aisen: Coih- aique Alto, 4.5 km E (133082, 133083-skel, 133085-skel, 133086). Magallanes: Ultima Es- peranza, Laguna Lazo (50584-50586, 50588- 50590, 50593-skel, 50595-50599); Lago Sar- miento (50583). Total: 18. Neotomys ebriosus— ARGENTINA. Jujuy: Si- erra de Zenta (41282). PERU. Pasco: Chigrin (24776-24778); La Quinua (24775). Ancash: Re- cuay Ticapampa (81283). Cuzco: Marcapata, Ccolini (75580). Junin: Paccha (64345). Puno: Hac. Collacachi (49708); Have (107824, 107842 -skel); Yunguyo (51261, 51263). Total: 13. Reithrodon auritus evae— ARGENTINA. Ne- uquen: Estancia Alicura (mvz 151033); Lago Na- huel Huapi, 11 km NNE (mvz 165853, 169013). Rio Negro: San Carlos de Bariloche, 18 km SE (mvz 1 62272); Comallo, 8 km WSW (mvz 1 6403 1 ). Total: 5. Reithrodon auritus pachycephalus — CHILE. 106 FIELDIANA: ZOOLOGY Aisen: Chile Chico (134178; 134188, 134189, 134225, 134226, 134228, 134229, 134231-skels; 134232, 134235); Coihaique Alto (134187-skel, 134192; 134196, 1 34202 -skels; 134204, 134205, 134207, 134210, 134213, 134222, 134224). Ma- gallanes: Pta. Arenas (124426— holotype); Rio Verde (50570-50576). Total: 29. Reithrodon typicus typicus— URUGUAY. Lav- alleja: Minas, Arroyo Polanco (27707-27709). Rocha: Castillos (27704). San Jose: Puerto Arazati (27653). Trienta y Tres: Quebrada de los Cuervos (27705, 27706). Total: 7. Other Specimens Examined for Phylogenetic Analyses Old World "Cricetids" Geronimo (35182-35186). GUATEMALA. Esuintla: Finoa St. Christina (7350 1 -skel). HON- DURAS (43308 -skel). MEXICO. Chiapas: Ocosingo (64186). PANAMA. Canal Zone: Rod- man Ammo Depot (usnm 396407). Chiriqui: Cer- ro Punta Casa Tillfy (usnm 323881). Darien: La Laguna (usnm 338266), El Aguacate (usnm 503722), Bocas del Toro (usnm 323880), Cerro Atul (usnm 306974). Total: 16. Tylomys nudicaudus— GUATEMALA. Chi- maltenango: Yerocapa, Finca Recreo (64568— skel, 64569). MEXICO. Chiapas: Palenque (66949). Oaxaca: San Gabriel Mixtapec, 23 mi N (ummz 114186, 114187— skels). Veracruz: Cerro Balza- pote (127151). msu lab colony (ummz 159340, 159341— skels). Zoo specimens (60029, 60030, 60767, 1048 15 -skels). US National Zoo (usnm 398072, 398073, 520882, 520883). Total: 16. Subfamily Calomyscinae Calomyscus baluchi— AFGHANISTAN. Bam- ian: 7.5 mi W Shibar Pass (102956, 102957, 102959); S. Atallah (102960-102962, 102964). PAKISTAN. Malakand: Swat, Karakar Pass (140403-1 40407 -skels). Total: 12. Subfamily Cricetinae Cricetulus migratorius— IRAN. Azerbaijan: Re- zaiyeh (57893, 57900, 96957-96961). Tehran: DoAb (96956). Total: 8. Mesocricetus auratus— Asia: captive (122237— skel); domesticated (571 14— skel). Total 2. Phodopus sungorus— Asia: zoo specimens (58804, 58983, 58984, 134492 -skels); domesti- cated (msu 34350, 35465— skels). Total 6. Subfamily Neotominae Neotomafloridana— USA. Arkansas: Logan Co., Magazine Mtn. (67699); Scott Co., Fourche La Fave River (67700); Stone Co., Marcella (63994, 63996). Illinios: Union Co., Pine Hills (64333- skel, 64335). Total: 6. Ochrotomys nuttalli— USA. Illinois: Alexander Co., Olive Branch (2 1 1 98 — skel). Louisiana: Cald- well Co., Columbia (16486-16488, 16490). North Carolina: Buncombe Co., Weaverville (5265). To- tal: 6. Peromyscus leucopus— USA. Illinois: Johnson Co., Ozark (1 5745-1 5747, 1 5752-skel); Pope Co., Golconda (15708, 15709); Union Co., Cobden (139895 -skel). Total: 7. Scotinomys teguina— COSTA RICA. Puntar- enas: Monteverde (128560-128563 — skels, 128564-128566). Total: 7. Subfamily Mystromyinae Mystromys albicaudatus -SOUTH AFRICA. Transvaal: Johannesburg (38147). Total: 1. New World "Cricetids" Subfamily Tylomyinae Nyctomys sumichrasti— COST A RICA. Puntar- enas: Monteverde (usnm 559055, 556461); San Tribe Akodontini Akodon albiventer— BOLIVIA. Potosi: Uyumi (mvz 120233— skel). CHILE. Tarapaca: Arica 72 km E (129981-129983-skels, 129986); Putre (1 29992-1 29993-skels). PERU. Moquegua: To- quepala (mvz 145543 — skel). Puno: Yunguyo (51300). Tacna: Tarata (107578-107581, 107600, 107618, 107621, 107644). Total: 17. Akodon boliviensis—PERU. Puno: Have, 5 km STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 107 W (107869, 107882, 107886, 107889, 107892); Santa Rosa, 6 km W (107917, 107928, 107976- skels), 12 km S (mvz 171615, 171617, 171618, 1 7 1 620, 1 7 1 62 1 - skels); Yunguyo (5 1 294-5 1299). Total: 19. Chroeomys andinus— CHILE. Antofagasta: Po- cos (mvz 1 19554— skel). Tarapaca: Parque Nac. Lauca, Parinacota (130001, 130002-skel, 130004-skel). PERU. Moquegua: Torata (107511, 107516, 107522, 107523, 107525, 107526, 107540, 107541). Total: 12. Chroeomys jelskii— PERU. Arequipa: Cailloma (49767-skel; mvz 174281, 174283, 174287- 174289 -skels). Puno: Macusani (mvz 173249, 173251, 173255). Santa Rosa (107919, 107921, 107931, 107932 -skels). Total: 13. Oxymycterus hispidus — ARGENTINA. Mi- siones: Rio Parana, Caraguaytay (26753-26757; 26841, 26856, 26857 -topotypes); Pto. Aguirre (23843). Total: 9. Tribe Ichthyomyini Anotomys leander— ECUADOR. Napo: Papal- lacta, 6.9 km W (ummz 1 26926, 1 55598-1 55630- skels). Pichincha: Chinchin Cocha (53367). Total: 8. Ichthyomys hydrobates— COLOMBIA. Cauca: Chisquio (90293). VENEZUELA. Merida: La Mu- cuy (ummz 156375 — skel). Total: 2. Neusticomys monticolus— COLOMBIA. Antio- quia: Santa Barbara (71219-71223); Urrao (7 1 2 1 8 - skel). Huila: San Agustin (7 1 224, 71225). ECUADOR. Napo: Papallacta (ummz 155604- 155606— skels). Pichincha: Old Santo Domingo Trail (ummz 126299, 155789, 155790, 155793- skels). Total: 15. Tribe Oryzomyini Holochilus brasiliensis— BOLIVIA. Beni: mouth Rio Baures (amnh 2 1021 8-2 10223 -skels). PAR- AGUAY. Presidente Hayes: Chaco, 15 km NNW (ummz 125997-126003, 126005 -skels). PERU. Loreto: Rio Amazonas (88913-88917); Yarina- cocha (55471, 55476, 62089). Total: 22. Neacomys spinosus— COLOMBIA. Putumayo: Mecaya (7 1 784— skel). PERU. Cuzco: Paucartam- bo, 72 km NE (ummz 160544— skel). Madre de Dios: Rio Alto Madre de Dios (ummz 160545 — skel). Pasco: Puerto Victoria (5 1358— skel). Puno: Bella Pampa (mvz 1 16665 — skel); Sagrario (52495 -skel); Rio Cayumba, Hac. Exito (24761- 24763). Total: 9. Nectomys squamipes—ROlAVlA. La Paz: Al- coche (117119). BRAZIL. Sao Paulo: Barra do Rio Juquia (93046-93048); Ilha do Cardoso (141630- 141633,141636— skels); Primeiro Morro (94393- 94379); Ribeirao Fundo (94395); Rocha (94400, 94402 -skels); Sao Sebastiao (18200). COLOM- BIA. Antioquia: Bella vista (701 10,70111, 70113— skel). Total: 20. Oligoryzomys fulvescens— COST A RICA. Pun- tarenas: Finca Helechales (usnm 547949). GUA- TEMALA. Chiquimula: Esquipulas (73546- 73548 -skels). MEXICO. Oaxaca: San Gabriel (amnh 190328 — skel). Puebla: Huachinango (6 1833, 6 1834). Veracruz: Achotal( 14 105-14 108, 15882X). PANAMA. Cerro Azul (usnm 305677). Total: 11. Oryzomys capito— ECUADOR. Napo, San Jose dePayamino( 125052, 125058, 125059, 125063- skels). PERU. Cuzco: Quincemil (75222, 75255, 75260, 75270). Madre de Dios: Manu (139864, 139865, 139868, 139869 -skels). Total: 12. Oryzomys palustris— USA. Florida: Highlands Co., Lake Istikpogo (amnh 2425 1 7, 2425 1 8), Lake Placid (amnh 242519, 242521, 242524). Missis- sippi: Copian Co., Burnell (48450, 48452-48455). New Jersey: Salem Co. (amnh 232365). Texas: Jefferson Co., Hildebrandt Acres ( 1 34427, 1 34428). Total: 14. Pseudoryzomys simplex— BOLIVIA. El Beni: San Joaquin (1 18810). PARAGUAY. Chaco: Ta- caagle (34236). Presidente Hayes: Villa Hayes, 24 km NW (ummz 133913). Total: 3. Zygodontomys brevicanda— COLOMBIA. Bo- livar: Socorre, upper Rio Sinu (69152— skel). PANAMA. Santa Rita de le Charrero (msu 20669 -skel). SURINAM. Brokopondo: Kwak- oegron (95688, 95784-skels; 95788). TRINI- DAD. Cuara (5348). Princetown (5349-5351- topotypes). VENEZUELA. Zulia: Empalado Sa- bana (18740- skel). Total: 10. Tribe Scapteromyini Kunsia tomentosus—BOlAYlA. Beni: San Joa- quin (122710, 122711). Total: 2. Scapteromys tumidus— BRAZIL. Rio Grande do Sul (amnh 235430-235432-skels). PARA- 108 FIELDIANA: ZOOLOGY GU AY. Cordillera: Tobati(uMMZ 125954, 125956, 137071-skels). URUGUAY. Canelones: Bal- neario, Salinas (122712, 122713). San Jose: Rio Santa Lucia (122714; amnh 188783, 188784- skels). Taecuarembo: Rio Negro (amnh 188782). Total: 13. Thomasomys baeops— COLOMBIA. Huila: San Agustin (71466, 71467, 71472, 71476). ECUA- DOR. Azuay (amnh 47677, 6 1 925, 6 1 953); El Oro (amnh 47699); Loja (amnh 61363). Total: 9. Thomasomys rhoadsi — ECUADOR. Pichin- cha: Cerro Antisana (43246-43250); (amnh 213548-skel). Total: 6. Tribe Sigmodontini Sigmodon hispidus- BRITISH HONDURAS. Cayo, 12 km S (ummz 62985 -skel). MEXICO. Chiapas: Bochil (ummz 92598— skel). Veracruz: Tenochtitlan (ummz 116335, 116336, 116338— skels). USA. Florida: Alachua Co., Gainesville (7955-7963). Georgia: Camoen Co., St. Marys (7953); Lanier Co., Oldfield (135121, 135122- skels); Lowndes Co., 1-75 and GA-31 (135123- 135 125 -skels). Louisiana: Hackley (16383- 16386, 16388). New Mexico: Otero Co., near Tularosa (125371, 125373-skels). Total: 27. Tribe Wiedomyini Wiedomys pyrrhorhinos — BRAZIL. Ceara: Ibiapaba (25249). Pernambuco: Exu (136941); Garanhuns (136942). Locality unknown (usnm 538306, 538314, 538382, 538386-538388). To- tal: 9. Thomasomyine Group Chilomys instans— COLOMBIA. Huila: Las Bardas (71493); San Agustin (71499, 71609). EC- UADOR. Cafiar: Chical (amnh 62922 -skel). Pi- chincha: Saloya (53403); Volcan Pichincha (53405). VENEZUELA. Merida: Paramo Tambor (22 172 -skel). Total: 7. Rhipidomys latimanus— COLOMBIA. Antio- quia: San Jeronimo (70235, 70237, 70238-skels, 70241, 70242). Huila: Pitalito(71710-skel). EC- UADOR. Imbabura NE Penahevva (ummz 77245, 77247 -skels). Total: 8. Thomasomys aureus— BOLIVIA. Cochabamba (amnh 260422). La Paz: Yerbani (ummz 1 55942— skel). COLOMBIA. Antioquia: SE Medellin (70330-skel); Ventanas (70321 -skel). Caldas: Termales (71263, 71264). PERU. Cuzco: Limac- punco (75228, 75230-75235); Paucartambo, 72 km NE (mvz 16671 1 -skel; ummz 160575-skel). Total: 15. Sigmodontinae incertae sedis Punomys lemminus— PERU. Arequipa: Huay- larco (mvz 116036). Puno: Abra Aricoma (mvz 139588, 139589); Limbani, 8 mi. SSW (mvz 114757, 114758, 116190-116194); San Antonio de Esquilache (49710— holotype). Tacna: Tarata, 20 km NE (mvz 1 15948). Total: 12. Other Specimens Examined for Vertebral Counts (Table 5) Aepeomys lugens— VENEZUELA. Merida (usnm 387955). Total: 1. Akodon {Abrothrix) longipilis— ARGENTINA. Rio Negro (mvz 155725, 155726, 155728, 155729, 1 63364); Santa Cruz (ummz 1571 54). CHILE. Val- paraiso (130905, 130907-130910). Total: 11. Akodon {Abrothrix) sanborni— CHILE. Chiloe (127565, 127566, 127568, 127569, 127572); Osorao (mvz 154128, 154130). Total: 7. Akodon aerosus— PERU. Cuzco (mvz 166777- 166779, 166784); Puno (mvz 173172, 173174, 173175, 173180). Total: 8. Akodon azarae— ARGENTINA. Buenos Aires (22233); Corrientes (mvz 166106— skel); La Pam- pa (mvz 173730— skel). Total: 3. Akodon cursor — BRAZIL. Rio de Janeiro (26626); Pernambuco (123060); Sao Paulo (141606-141614). Total: 11. Akodon mollis — PERU. Ancash (129212, 129213, 129215, 129216). Total: 4. Akodon neocenus— ARGENTINA. La Pampa (mvz 173726, 173732, 182025). Total: 3. Akodon olivaceus — ARGENTINA. Neuquen (mvz 163455, 166063); Rio Negro (mvz 155752- 155754). CHILE. Aisen (22230, 22237, 22238); Chiloe (132169-132173, 132275, 132278, 132279); Valdivia (mvz 154125-154127). Total: 19. STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 109 Akodon puer— PERU. Arequipa (mvz 174009, 174100); Puno (mvz 173238, 173240, 173241, 173244, 173245). Total: 7. Akodon subfuscus — PERU . Ayacucho (mvz 174246-174248); Puno (mvz 173229, 173234- 173236). Total: 7. Akodon nr/cAi— TRINIDAD AND TOBAGO. Tobago (usnm 540711). VENEZUELA. Aragua (usnm 517596, 517599, 517600); Bolivar (usnm 448568). Total: 5. Akodon torques— PERU. Cuzco (mvz 166744- 166751, 166760, 166762). Total: 10. Akodon xanthorhinus — ARGENTINA. Rio Negro (mvz 158401); Tierra del Fuego (usnm 482127, 482129, 482130, 482132-482134). CHILE. Magallanes (127301-127305). Total: 12. Akodon (Deltamys) kempi— URUGUAY. Ro- cha (amnh 206139, 206140, 206142). Total: 3. Akodon (Microxus) bogotensis— VENEZUELA. Merida (usnm 3746 1 2); Tachira ( 1 8678). Total: 2. Akodon {Microxus) mimus— BOLIVIA. Cocha- bamba (amnh 260429, 260586, 260587, 260592, 260593, 260595-260599); La Paz (ummz 126779, 1 55946-1 55948). PERU. Puno (mvz 1 7 1 750). To- tal: 15. Akodon (Thaptomys) nigrita— PARAGUAY. Itapua(uMMZ 125959-125963, 125968). Total: 6. Baiomys musculus — MEXICO. Veracruz (56145). Total: 1. Bolomys amoenus— PERU. Puno (49750; mvz 173191-173193, 173198-173201). Total: 8. Bolomys lasiurus — PARAGUAY. Paraguari (ummz 133947, 137083-137087). Total: 6. Bolomys obscurus— ARGENTINA. Buenos Ai- res (msu 17387). Total: 1. Brachytarsomys albicauda —MALAGASY (amnh 100690-100692). Total: 3. Brachyuromys ramirohitra —MALAGASY (5623). Total: 1. Calomys musculinus— ARGENTINA. Buenos Aires (msu 1 9398); Rio Negro (msu 1 9 1 86, 1 9 1 87, 19189). Total: 4. Cricetulus barabensis —Locality unknown (USNM 521109). Total: 1. Cricetulus longicaudatus — CHINA. Qinghai (usnm 449101, 4491 15—4491 18). Total: 5. Cricetus cricetus— GERMANY, (amnh 31814). POLAND (usnm 494 1 3). US National Zoo (usnm 294370, 294371). Total: 4. Chelemys macronyx— ARGENTINA. Rio Ne- gro (mvz 174385-174387). CHILE. Aisen (132957-132959, 132962, 132963); Magallanes (50530). Total: 9. Delomys dorsalis— BRAZIL. Sao Paulo (145370, 145371). Total: 2. Delomys sublineatus — BRAZIL. Sao Paulo (141628, 141629). Total: 2. Eliurus myoxinus— MALAGASY. Ampitambe (amnh 31801). Total: 1. Geoxus valdivianus— ARGENTINA. Rio Ne- gro (mvz 155817, 163382, 172206); Santa Cruz (usnm 49522). CHILE. Osorno (127726, 133090, 133099-133101). Total: 6. Gymnuromys roberti — MALAGAS Y (usnm 49670, 49671). Total: 2. Holochilus brasiliensis vulpinus— ARGENTI- NA. Entre Rios (ummz 166268, 166269, 166399, 166692). URUGUAY. Canelones (amnh 206362); Sori (amnh 206372). Total: 6. Holochilus chacarius— PARAGUAY '. Alto Par- aguay (ummz 166255, 166256, 166259, 166267, 166314, 166438, 166450). Total : 8. Ichthyomys tweedii — EUCADOR. Pichincha (ummz 126300, 155782, 155786, 155787). Total: 4. Lundomys molitor— URUGUAY. Trienta y Tres (amnh 206392, 296393). Total: 2. Macrotarsomys bastardi — MALAGASY. Fi- narantsoa (usnm 328800, 328806); Toliara (usnm 578716-578718). Total: 5. Melanomys caliginosus— COLOMBIA. Meta (amnh 1 5497). Santa Marta (usnm 280606). COS- TA RICA. Heredia (128471, 128472, 128476, 128477, 128484, 128485, 128488, 128489). To- tal: 10. Microryzomys altissimus— ECUADOR. Cariar (amnh 63052); Imbabura (125043); Pichincha (amnh 213549). Total: 3. Microryzomys minutus — BOLIVIA. Cocha- bamba (amnh 260419). ECUADOR. Tungurahua (47597). VENEZUELA. Merida (usnm 374373, 374380, 374443); Sucre (amnh 69894, 69896). Total: 7. Mystromys albicaudatus — Location unknown (usnm 396240). Total: 1. Neacomys guianae — BRAZIL. Para (usnm 549553). FRENCH GUYANA. Paracou (amnh 266555-266558). Total: 5. Neacomys spinosus — BOLIVIA. Santa Cruz (amnh 261987, 261989-261991, 263815). EC- UADOR. Napo (usnm 534372, 574567). Total: 7. 110 FIELDIANA: ZOOLOGY Neacomys tenuipes— COLOMBIA. Antioquia (usnm 499556, 499557, 499559). VENEZUELA. Aragua (usnm 517585). Total: 4. Nesomys audeberti— MALAGASY. Finarant- soa (usnm 448946, 449232). Total: 2. Nesomys rufus — MALAGASY. Finarantsoa (usnm 448954, 448962^148964). Total: 4. Nesoryzomys narboroughi— ECUADOR. Ga- lapagos (30844; usnm 364938, 364939). Total: 3. Nesoryzomys indefessus— ECUADOR. Gala- pagos (30853). Total: 1. Notiomys edwardsii— ARGENTINA. Rio Ne- gro (mvz 163065). Total: 1. Oecomys bicolor— BOLIVIA, La Paz (ummz 155945); Santa Cruz (amnh 246808, 262009- 2620 11,26381 6). COLOMBIA. Caqueta (72093). ECUADOR. Napo (125044, 125045, 125047). GUYANA. Muzaruni-Potaro (amnh 64130). PANAMA. San Bias (usnm 335532, 335533). PERU. Madre de Dios (ummz 160550). Total: 14. Oecomys concolor — VENEZUELA. Aragua (usnm 399535, 517572, 517573). Total: 3. Oecomys mamorae — BOLIVIA. Santa Cruz (amnh 262013). Total: 1. Oecomys paricola— GUYANA. Mazaruni-Po- taro (amnh 48142). Total: 1. Oecomys roberti — BOLIVIA. Pando (amnh 248996, 262825). BRAZIL. Para (usnm 549537, 549539, 547540). Total: 5. Oecomys superans — COLOMBIA. Caqueta (125064). PERU. Pasco (amnh 213540, 232140). Total: 3. Oecomys trinitatis— PANAMA. Darien (usnm 305708, 310549, 310550). VENEZUELA. Merida (21823). Total: 4. Oligoryzomys andinus — BOLIVIA. Oruro (amnh 260405); Potosi (amnh 255946). PERU. Ancash (fmnh 129240). Total: 3. Oligorzoymys chacoensis — BOLIVIA. Chuquis- aca (amnh 262126, 126127, 262129-262131). PARAGUAY. Chaco (ummz 125539-125542). Total: 9. Oligoryzomys rfe///co/fl - URUGUAY. Duraz- no (amnh 205955, 205957, 205959, 205960). To- tal: 4. Oligoryzomys destructor— PERU '. La Libertad (31702). Total: 1. Oligoryzomys eliurus— BRAZIL. Mato Grosso (amnh 134899). Total: 1. Oligoryzomys flavescens— URUGUAY. Rocha (amnh 205597-205601). Total: 5. Oligoryzomys longicaudatus — CHILE. Co- quimbo (133215, 133217, 133218; 133596- 133599). Total: 7. Oligoryzomys magellanicus — ARGENTINA. Tierra del Fuego (usnm 482125, 482126). Total: 2. Oligoryzomys microtis— BOLIVIA. Beni (amnh 266947-255950, 255952, 255953). Total: 6. Oligoryzomys microtis fornesi— PARAGUAY. Canendiyu (ummz 126013, 126082, 133826, 137018, 137028). Total: 5. Oligoryzomys nigripes— ECUADOR. El Oro (amnh 47744, 47745); Pasaje (amnh 61313). PARAGUAY. Paraguari (ummz 133880, 133882, 137041, 137042). Total: 7. Oryzomys albigularis— COSTA RICA. Heredia (128164, 128462). Puntarenas (128468, 128470, 128573; usnm 559053). ECUADOR. Caiiar (amnh 63330); Pichincha (94979). PANAMA. Darien (usnm 338207). Total: 9. Oryzomys alfaroi— PANAMA. Darien (usnm 383247, 383256, 383258). GUATEMALA. Es- quintla (usnm 275364). Total: 4. Oryzomys bombycinus— PANAMA. Cerro Azul (usnm 305649, 305653). Total: 2. Oryzomys buccinatus— PARAGUAY. Canen- diyu (ummz 133798); Cordillera (ummz 126005, 126006). Total: 3. Oryzomys capito— BOLIVIA. Beni (amnh 209961, 209968, 210016-210018). Total: 5. Oryzomys chapmani— MEXICO. Oaxaca (amnh 254698-254700). Total: 3. Oryzomys couesi— GUATEMALA. Esquintla (usnm 275365). NICARAGUA. Managua (amnh 178028, 178030). Total: 3. Oryzomys intermedins— BRAZIL. Sao Paulo (94549, 94550, 141637-141641). Total: 7. Oryzomys keaysi — BOLOVIA. Cochabamba (amnh 260346-260349, 260351). Total: 5. Oryzomys melanotis— MEXICO. San Luis Po- tosi (amnh 254713-254716). Total: 4. Oryzomys «///#«£— PARAGUAY. Itapua (ummz 126008). Total: 1. Oryzomys polius— PERU. Amazonas (129242, 129243, 129245). Total: 3. Oryzomys ratticeps— PARAGUAY. Canendiyu (ummz 1 33794); Itapua (ummz 1 36007); Missiones (ummz 125458, 125459). Total: 4. Oryzomys subjlavus—BOlAYlA. Beni (amnh 210024-210027). Total: 4. Oryzomys talamancae— COLOMBIA. Choco STEPPAN: REVISION OF THE TRIBE PHYLLOTINI 111 (72408). EUCADOR. Loja (amnh 61335). VEN- EZUELA. Zulia (usnm 448597, 448605, 448607- 448609). Total: 7. Oryzomys xantheolus — PERU. La Libertad (44433). Total: 1. Ototylomys phyllotis— BELIZE. Orange Walk District (58546). GUATEMALA. Alta Verapaz (64564, 64565); Peten (ummz 63556); San Miguel (ummz 110907). MEXICO. Yucatan (amnh 91222). Total: 6. Ototylomys phyllotis fumeus— NICARAGUA. Chinandega (ummz 1 15519). Total: 1. Oxymycterus delator— PARAGUAY. Canen- diyu (ummz 126079, 126085-126087), (amnh 248437). Total: 5. Oxymycterus inca —BOLIVIA. Santa Cruz (amnh 260604, 260605, 263344-263347, 263349- 263353). Total: 11. Oxymycterus paramensis— ARGENTINA. Ju- juy (22234). BOLIVIA. Entre Rios (usnm 271399). PERU. Puno (52476). Total: 3. Oxymycterus rufus— ARGENTINA. Buenos Aires (usnm 236296). BOLIVIA. La Paz (amnh 249003-249005); Tarija (amnh 262968). BRA- ZIL. Santa Catarina (usnm 236672). URUGUAY. Canelones (amnh 206168, 206169); Cerro Largo (amnh 206177). Total: 9. Rheomys raptor — COSTA RICA. San Jose (UMMZ 1 1 1985, 1 1 1986, 1 12300, 1 12301). To- tal: 4. Rheomys thomasi— EL SALVADOR. Chala- tenanio (mvz 98811, 98813, 98815); San Miguel (MVZ 98799-98801, 99805, 131998). GUATA- MALA. Huehuetenango (ummz 1 18235). Total: 9. Rheomys underwoodi— COSTA RICA. Alajuela (ummz 115389, 115460). Total: 2. Rhipidomys couesi — BOLIVIA. Chuquisaca (amnh 263919); La Paz (amnh 262991, 262992); Tarija (amnh 246827). BRAZIL. Mata Grosso (amnh 134522). TRINIDAD AND TOBAGO. Trinidad (amnh 212140, 212141, 235071). Total: 8. Rhipidomys fulviventer— COLOMBIA. Antio- quia (71720). Total: 1. Rhipidomys macconnelli— VENEZUELA. Bo- livar (mvz 160083). Total: 1. Rhipidomys mastacalis — BRAZIL. Goyaz (amnh 1 34524); Para (usnm 549554). VENEZUE- LA. Bolivar (usnm 448620, 448621). Total: 3. Rhipidomys scandens — PANAMA. Darien (usnm 338265). Total: 1. Rhipidomys venezuelae— VENEZUELA. Ara- gua (USNM 5 1 7589, 5 1 759 1 , 5 1 7592). Zulia (usnm 448629). Total: 4. Rhipidomys venustus— VENEZUELA. Merida (usnm 387908). Total: 1. Sigmodon alleni— MEXICO. Guerrero (ummz 109664); Michoacan (ummz 109660, 119602, 119604). Total: 4. Sigmodon fulviventer— USA. Arizona (ummz 85455, 85456). Total 2. Sigmodon leucotis— MEXICO. Oaxaca (ummz 96298; 127152). Total: 2. Sigmodon ochrognathus— USA. Texas (ummz 79140, 79153-79155). Total: 4. Sigmodontomys alfari — COLOMBIA. Pal- mares del Pacifico (usmn 483981). ECUADOR. Camolima (ummz 7724 1). PANAMA. Tacaracuna (usnm 310588, 310589, 310590). Total: 5. Thalpomys lasiotis— BRAZIL. Distrito Federal (128327). Total: 1. Thomasomys cinereus— ECUADOR. El Oro (amnh 47659^17661, 47667). Total: 4. Thomasomys daphne— BOLIVIA. La Paz (ummz 155894). PERU. Cuzco (ummz 160580). Total: 2. Thomasomys gracilis— PERU. Cuzco (ummz 160584). Total: 1. Thomasomys hylophilus— COLOMBIA. Norte de Santander (18586). VENEZUELA. Tachira (usnm 442305). Total: 2. Thomasomys oreas — PERU. Cuzco (ummz 160587). Total: 1. Thomasomys paramorum — ECUADOR. Pi- chincha (amnh 213545-213547; fmnh 47595, 47596, 125061). Total: 6. Thomasomys pyrrhonotus— ECUADOR. Cafi- ar (amnh 63316, 63326). Total: 2. Tscherskiatriton— NORTH KOREA. Kumhwa (usnm 294636). Total: 1. Tylomys fulviventer — PANAMA. Darien (usmn 310600, 310602-310605). Total: 5. Tylomys mirae— COLOMBIA. Boyaca (71216); Caldas (71215). Total: 2. Tylomys panamensis— PANAMA. Canal Zone (usnm 396409); Cerro Azul (usnm 306972); (usnm 503720, 503721). Total: 4. Tylomys watsoni— COSTA RICA. Cartago (usnm 566460). Total: 1. 112 FIELDIANA: ZOOLOGY ted Listing i »f ZotilOH ictotyp ) 1990. Lawrenc 2 tables. Panicuh ;k Foode me Macaques Zoology, n.s., Museum, Stockholm . Pattei :.r. , ''let . ' •■ ime: u ■ ta >h linifo tti ; (< '■ le ■ lolotsv, ii.s.. no in 67 199 ! • • tatus, Relative Abundant and Behavior i ; ilivia. Bv Susan E. Davis Fieldiana Zool T)\ n.s no. 1,1993 3 pages HHus., jcation number and » its add current destination he 1 subsidiary >s all reque: ts 3 ' oui ; • ice list. \tl ord( i ; rnusl , . rder i in p< ; able in '• ; > ■ icck: k. Prices and terms sxii i ;. brar - Pubi cations '>. vision Ro< ■ elt •■'■ ad : ' Lake Shore Dj ( hi< y [Uii • is 6060^-2498, I CKMAN )ERY INC. i i NOV 96