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The Microtine Rodents of the 

Cheetah Room Fauna, Hamilton Cave, 

West Virginia, and the 

Spontaneous Origin of Synaptomys 

By CHARLES A. REPENNING and FREDERICK GRADY 

Remarkably primitive rodents indicate the need for 

revisions in evolutionary concepts of bog lemmings and 

heather votes 

U.S. GEOLOGICAL SURVEY BULLETIN 1853 
DEPARTMENT OF THE INTERIOR 

DONALD PAUL HODEL, Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1988 

For sale by the 

Books and Open-File Reports Section 

U.S. Geological Survey 

Federal Center, Box 25425. 

Denver, CO 80225 

Library of Congress Cataloging in Publication Data 

Repenning, Charles Albert, 1922-

The microtine rodents of the Cheetah Room Fauna, Hamilton Cave, West 

Virginia, and the spontaneous origin of Synaptomys. 

(U.S. Geological Survey bulletin ; 1853) 

Bibliography: p. 

1. Cricetidae, Fossil-West Virginia-Hamilton Cave. 2. Paleontology-West 

Virginia-Hamilton Cave. I. Grady, Frederick. II. Title. Ill. Series. 

QE75.B9 no. 1853 [QE882.R6] 557.3 s (569' .323] 88-600217 

Any use of trade names is for descriptive purposes only and does not imply endorsement by the U.S. Ceological Survey 
CONTENTS 

Abstract 1 

Introduction 1 

Age of the fauna 2 

Terminology 2 

Abbreviations 2 

Acknowledgments 3 

Systematics 3 

Subfamily Arvicolinae, Bonaparte, 1837 3 

Tribe Arvicolini, Kretzoi, 1955 3 

Genus Mimomys, Forsyth Major, 1902 4 

Subgenus Cromeromys, Zazhigin, 1980 4 

Mimomys (Cromeromys) virginianus, n. sp. 5 

Genus Phenacomys, Merriam, 1889 S 

Subgenus Phenacomys, Merriam, 1889 7 

Subgenus Arborimus, Taylor, 1915 8 

Subgenus Paraphenacomys, new name 8 

Phenacomys (Paraphenacomys) brachyodus, n. sp. 10 

Genus Allophaiomys, Kormos, 1932 10 

Allophaiomys pliocaenicus Kormos, 1933 11 

Tribe Microtini, Simpson, 1945 11 

Genus Proedromys, Thomas, 1911 12 

Genus Lasiopodomys, Lataste, 1887 12 

Lasiopodomys deceitensis (Guthrie and Matthews, 1971) 14 

Genus Microtus, Schrank, 1798 14 

Microtus paroperarius Hibbard, 1944 15 

Tribe Pitymyini, Repenning, 1983 16 

Genus Pitymys, McMurtrie, 1831 16 

Pitymys hibbardi Holman, 1959 17 

Subfamily Ondatrinae, new form 18 

Tribe Ondatrini, Kretzoi, 1955 18 

Genus Ondatra, Link, 1795 18 

Ondatra annectens (Brown), 1908 19 

Subfamily Lemminae, Gray, 1825 19 

Tribe Synaptomyini, von Koenigswald and Martin, 1984b 19 

Genus Mictomys, True, 1894 22 

Genus Synaptomys, Baird, 1858 22 

Bog lemming history 25 

Summary and conclusions 26 

References cited 27 

Index 29 

FIGURES 

1. Sketch showing dentition of two species of Mimomys ( Cromeromys) 6 

2. Diagram showing inferred phylogeny of the Phenacomys lineage 8 

3-9. Sketches showing: 

3. First lower molars of Phenacomys 9 

Contents Ill 
4. First lower molars of Tribe Microtini 13 

5. First lower molars of Pitymys hibbardi 17 

6. Right lower first molars of the Tribe Synaptomyini and left 

lower first molars of the Tribe Lemmini 21 

7. Left lower first molars of living bog lemmings, occlusal views 22 

8. Left lower first molars of Mictomys 23 

9. Left lower first molars of bog lemmings from the Cheetah Room 

fauna of Hamilton Cave 23 

10. Diagram showing inferred phylogeny of the Synaptomyini 25 

IV Contents 
The Microtine Rodents of the 

Cheetah Room Fauna, Hamilton Cave, 

West Virginia, and the Spontaneous 

Origin of Synaptomys 

By Charles A. Repenning and Frederick Grady1 

Abstract 

The Cheetah Room fauna of Hamilton Cave, West 

Virginia, is a full complement of vertebrates including microtine 

rodents. The microtines are represented by a new species of 

the subgenus Mimomys (Cromeromys) that was formerly known 

only from Eurasia, a new species of Phenacomys similar toP. 

albipes, Allophaiomys p/iocaenicus, Lasiopodomys deceitensis 

that was formerly known only from the arctic region, Microtus 

paroperarius, Pitymys hibbardi, Ondatra annectens, a bog lemming intermediate between the genera Mictomys and Synaptomys, and Atopomys salve/in us. The transitional morphologic 

variations, between ancestor and descendants, of Phenacomys, 

the bog lemming, and Pitymys hibbardi, as well as the presence 

of Microtus paroperarius, are the principal reasons for an age 

assignment of between 740,000 and 850,000 years. 

The history of the bog lemmings begins 4 million years 

ago in southeastern Europe with Plioctomys mimomiformis, of 

unknown ancestry. This species dispersed eastward across Asia 

to Beringia, where its youngest record is 2.4 million years old; 

during this first 1.6 million years of the history there was no 

detected morphologic change in the dentition. However, between 3 and 2.6 million years ago these bog lemmings also 

dispersed southward from Beringia to the United States on both 

sides of the Rocky Mountains, during which dispersal they 

evolved east of the cordillera into a new species, Plioctomys 

rinkeri, and to the west into a new genus and species, Mictomys 

vetus. 

By 2.0 million years ago Mictomys spread eastward 

around the southern end of the Rocky Mountains and Plioctomys became extinct. More than 1 million years later Synaptomys abruptly evolved out of a southeastern population of 

Mictomys in one of the more remarkable morphologic transitions known in vertebrate paleontology, as recorded in the 

Cheetah Room fauna. 

Publication approved by the Director, U.S. Geological Survey, April 

12, 1988. 

1

National Museum of Natural History, Mail Stop 121, Smithsonian 

Institution, Washington, D.C. 20560. 

INTRODUCTION 

Fossil rodents were discovered in the Cheetah 

Room of Hamilton Cave, John Guilday Cave Preserve, 

Pendleton County, West Virginia, in 1981 by Miles Drake 

and Carole Sneed of the Potomac Speleological Club. The 

name of the room derives from the later discovery of the 

skeleton of a cheetah-like felid. A large variety of fossil 

mammals and other vertebrates is known from the 

Cheetah Room fauna and comes from the top 75 em of 

cave earth; most of the fauna is still under study. Seventyfive centimeters could represent an appreciable period of 

time, but no changes in the fauna were noted during 

excavation. 

The microtine fauna contains a new species of the 

genus Mimomys nearly identical to the European 

Mimomys tornensis Janossy and van der Meulen (1975), 

a new species of the genus Phenacomys that is related 

to P. albipes, Allophaiomys pliocaenicus, Lasiopodomys 

deceitensis, Microtus paroperarius, Pitymys hibbardi, 

Ondatra annectens, a bog lemming intermediate between 

Synaptomys and Mictomys, and Atopomys salvelinus. 

The last species is under study by Alisa Winkler and 

Frederick Grady and is not discussed here. 

Mimomys and Lasiopodomys are not known from 

faunas of central or western conterminous United States 

that are of the same approximate age; Pitymys hibbardi 

and Atopomys salvelinus represent two lineages that seem 

to have a fossil and, in the case of Pitymys, living distribution only in the eastern and central United States; and 

the suggested origin of the southern bog lemming is in 

the southeastern United States. These regional distributions suggest a provinciality that may be related to differing environments. Conversely, it would seem that 

Allophaiomys and Microtus paroperarius, known from 

the Rocky Mountains to the Atlantic, and Phenacomys, 

known from the Pacific to the Atlantic coasts, had 

broader environmental tolerances. The suggestion of a 

provincial environmental difference may bear on the 

Introduction 1 
spontaneous origin of Synaptomys, but no other external cause is yet recognized. 

Age of the Fauna 

Based upon the gradation between the bog lemmings Mictomys and Synaptomys, to be described, the 

Cheetah Room fauna is believed to be older than the 

Fyllan Cave fauna of Texas, which contains two 

specimens of Synaptomys cooperi (TMM 40682-629, a 

first lower molar, and TMM 40682-295, a second lower 

molar) and which is in reversely magnetized deposits 

(Alisa Winkler, written commun., 1987). The Cheetah 

Room fauna is thus considered to be older than the 

Brunhes Normal Polarity Chron, beginning 740,000 years 

ago. 

Although Microtus and Lasiopodomys are known 

from Canada and Alaska as much as 2.1 million years 

ago (Repenning and others, 1987), there is no record of 

them east of the Rocky Mountains in the conterminous 

United States until the beginning of the Nebraskan glaciations (as used by Repenning, 1984) 850,000 years ago. 

The oldest prior record of Microtus paroperarius in the 

lower-latitude United States is from the 820,000-year-old 

part of the Hansen Bluff faunal sequence of Colorado 

(Rogers and others, 1985). Although the sample of this 

species from the Cheetah Room fauna is very small, it 

more resembles that from Hansen Bluff than it does 

younger records. The Cheetah Room fauna is thus considered to be somewhat younger than 850,000 years but 

possibly no younger than 820,000 years. Lasiopodomys 

from the Cheetah Room fauna is the first record of this 

genus from the conterminous United States, but its older 

records from Canada and Alaska suggest some antiqUity. 

Individual variation in the dental morphology of 

the species Pitymys hibbardi from the Cheetah Room 

fauna overlaps that of both ancestral Allophaiomys pliocaenicus and the descendant species of Pitymys, and also 

suggests some antiquity, although the suggestion is vague 

in terms of radiometric years. Similarly, the stage of 

evolution of the new species of Phenacomys, to be 

described, is intermediate between 1. 7-million-year-old 

ancestors and 13,000-year-old and living descendants, 

although this condition is certainly more vague in terms 

of age. 

Terminology 

Although recently criticized for a lack of standardization (Martin, 1987), the terminology herein used for 

parts of the teeth is as standard as we consider possible. 

It is that used and explained by Repenning (1983) and 

is based upon those terms that seem most frequently used 

2 Microtine Rodents, Hamilton Cave, West Virginia 

in several languages of the Northern Hemisphere. There 

are, of course, conflicts in terminology: for example, 

reports in the Russian languages frequently refer to the 

"anteroconid complex" as the "paraconid section." 

When it appears that a non-English-language term has 

been applied more consistently and with better understanding than an English language term, such a term may 

be used: for example, due to the work of Wighart von 

Koenigswald, "Schmelzmuster" has a particular meaning, regarding the patterns of enamel rod orientation and 

their distribution throughout the enamel layer forming 

the surfaces of the cheek teeth, that would be lost by 

translation into the English. 

The evolution of dental terminology may be reviewed in Hinton (1926, p. 102-124), who was more 

concerned with homologies than with a standard terminology; Hibbard (1950, fig. 16), who was concerned with 

standardization; Repenning (1968, fig. 10), who was concerned with the origin of the features of the anteroconid 

complex (called "anterior cingulum"); van der Meulen 

(1973, p. 29-33, 52-59, and fig. 10), who was concerned 

with standardization by use of alphanumeric symbols; 

and Repenning (1983, p. 474), who was concerned with 

standardization of terms in the anteroconid complex. 

Martin's (1987) whimsical discussion of the standardization of terminology simply stated that he prefers 

the alphanumeric symbols. These symbols have proven 

cumbersome to some, requiring frequent reference to the 

explanation for translation, as perhaps is illustrated by 

the repetition of the explanation of van der Meulen's 

symbols appearing in most of his publications, as well 

as in most publications by other authors who use these 

symbols, as Martin (1987). We do not prefer them. 

Abbreviations 

Lower molars are indicated by a lower case "m" 

and upper molars by an upper case "M." 

For brevity, the abbreviation "m.y." is used in 

parenthetical statements to indicate "million years." 

Specimens are identified by the catalog numbers of 

the institution in which they are housed, preceded by one 

of the following abbreviations: 

F:AMNH: Frick collection: the American Museum of 

Natural History, New York. 

HNHMB: Hungarian Natural History Museum, 

Budapest. 

ISM: Illinois State Museum, Springfield. 

IVPP:AS: Institute of Vertebrate Paleontology and 

Paleoanthropology: Academia Sinica, Beijing. 

KU: University of Kansas, Museum of Natural History, 

Lawrence. 

TMM: Texas Memorial Museum, Austin. 

UA: University of Alaska, Fairbanks. 
UC: University of Colorado Museum, Boulder. 

UCMP: University of California Museum of Paleontology, Berkeley. 

UF/FGS: Florida State Museum, University of Florida, 

Gainesville; specimen formerly in the collection of 

the Florida Geological Survey. 

USGS: uncataloged specimens in the reference collection 

of the U.S. Geological Survey, Denver. 

USNM: National Museum of Natural History, 

Washington. 

ZZSD:PAN:C: Institute of Systematic and Experimental 

Zoology: Polish Academy of Science: Cracow. 

Acknowledgments 

The National Speleological Society, owner of 

Hamilton Cave, has supported and encouraged the 

studies of fossil vertebrates. Excavations of Hamilton 

Cave were financed in part by the National Geographic 

Society through a grant to Blaire VanValkenburgh, Bjorn 

Kurten, and Frederick Grady. In addition to Miles Drake 

and Carole Sneed, many other volunteers helped haul out 

sacks of fossil-bearing cave earth from Hamilton Cave, 

in particular Tom Kaye, Bob Hoke, Dave West, Donald 

Keller, and Cindy Keller. Anthony D. Barnosky, Thomas 

M. Bown, Robert S. Hoffmann, and Alisa J. Winkler 

read versions of the manuscript and provided many 

helpful suggestions. Jordi Agusti, Charles S. Churcher, 

Oldrich Fej far, Lawrence J. Flynn, Russell W. Graham, 

John E. Guilday, R. Dale Guthrie, Claude W. Hibbard, 

Robert S. Hoffmann, James G. Honey, J. Howard 

Hutchison, Murray L. Johnson, Kazimierz Kowalski, 

Robert A. Martin, Pierre Mein, Robert Purdy, Robert 

L. Rausch, Karel L. Rogers, Richard H. Tedford, S. 

David Webb, Melissa C. Winans, and Alisa J. Winkler 

provided specimens used in the study of the Cheetah 

Room microtines. 

SYSTEMATICS 

The classification here used follows that briefly 

discussed by Repenning (1987). The microtine (or arvicolid, as usually discussed) rodents are considered 

polyphyletic and consist of five separate cricetid subfamilies that independently evolved microtine-type cheek 

teeth out of low-crowned cricetid rodent teeth. The 

ancestries of three of these five subfamilies have been 

traced through the fossil record to different cricetid 

rodents with low-crowned cheek teeth; the two subfamilies with unknown ancestry are both lemmings, but 

otherwise they have no similarity in the fossil record and 

are grouped in separate subfamilies. 

These five subfamilies are subdivided into tribes by 

more or less conventional criteria. The word ''microtine'' 

is used as a descriptive term referring to the type of tooth 

common to all of these five cricetid subfamilies: a tooth 

with tall, triangularly prismatic cusps. 

Because this classification is relatively new, a 

diagnosis of the dental characters is provided for each 

discussed microtine taxon. These give only the diagnostic 

dental characters and are not concerned with diagnosis 

by other characters, although the authors believe that 

these other characters are conformable with the classification. Within the diagnoses, brackets are used for explanatory notes and are not to be considered part of the 

diagnosis. 

Several very useful diagnostic characters are lost 

with the development of rootless cheek teeth in the 

microtine rodents, such as: (l) relative dentine tract 

development, (2) relative vertical height of the individual 

reentrants on the buccal surface of ml, and (3) relative 

degree of wear required to obliterate islets and other 

enamel irregularities that are evident only in the early 

stages of wear. With the loss of these characters found 

only on rooted teeth, the lineage of a specimen is less easily determined and individual variability becomes more 

troublesome. As will become evident, the average condition of the population thus becomes more important in 

the identification of microtine species with rootless cheek 

teeth. 

Among microtines with rootless cheek teeth, it is 

commonplace to find some individuals of any population whose dental morphology overlaps that of closely 

related species. For this reason, small samples of fossil 

species often can be only questionably identified. Also 

for this reason, not only typical, but also extreme dental 

morphologies are illustrated herein. 

Family CRICETIDAE 

Subfamily ARVICOLINAE, Bonaparte, 1837 

(following Kretzoi, 1969) 

Dental diagnosis.-Cricetid rodents with hypsodont, triangularly prismatic cusps on their cheek teeth 

[microtines]; ml with posterior loop and three basic alternating triangles, differing from the Ondatrinae and the 

Dicrostonychinae; anteroconid complex with single 

rounded to globular cap, differing from the Prometheomyinae; M3 with alternating triangles differentiated, not 

lophate, differing from the Lemminae. 

Included tribes.-Arvicolini, Clethrionomyini, 

Lagurini, Microtini, and Pitymyini. 

Tribe ARVICOLINI, Kretzoi, 1955 

Dental diagnosis.-Arvicoline rodents with rooted 

cheek teeth, for the most part, differing from the Microtini, Pitymyini, and Lagurini; no additional triangles in 

Systematics 3 
the anteroconid complex of m1, differing from the 

Clethrionomyini; M3 with no more than two completely 

formed alternating triangles, differing from all tribes except some Lagurini. 

Included genera.-Allophaiomys, ?Aratomys, 

Arvicola, Borsodia, Hibbardomys, Kislangia, Mimomys, 

Phaiomys, Phenacomys, Promimomys, and Villanyia. 

Discussion.-The teeth of Arvicola are rootless, 

those of Phenacomys have additional triangles, and those 

of Allophaiomys (and Phaiomys) are rootless, but 

A/lophaiomys appears ancestral to both the Tribe 

Microtini and the Tribe Pitymyini. Rather than establish 

separate tribes for each of these three genera because they 

deviate from the above diagnosis, they are placed in the 

ancestral Tribe Arvicolini by default. 

Genus MIMOMYS, Forsyth Major, 1902 

Dental diagnosis.-Arvicolinine rodents with 

rooted cheek teeth, differing from Arvicola, 

A.llophaiomys, and Phaiomys; m1 with cap of 

anteroconid complex skewed lingually, differing from 

Villanyia and Borsodia, with primary wings and 

Mimomys Kante of anteroconid complex [marked x on 

fig. 1A] prominent, differing from Promimomys and, for 

the most part, Phenacomys, and with islet derived from 

a buccal reentrant preserved in most lineages and more 

persistent in early stages of evolution, differing from 

Phenacomys, Kislangia, Borsodia, and Villanyia; M3 

with one buccal triangle and basined posterior loop 

(becoming an islet with wear) or two alternating triangles 

and hooked, but not elongate, posterior loop formed by 

lingual breaching of basined posterior loop so that an islet 

does not form, differing from Villanyia and Borsodia, 

which have an elongate posterior loop. 

Included subgenera.-Cromeromys, Cseria, and 

Mimomys in Eurasia; Cosomys, Cromeromys, 

Ogmodontomys, and Ophiomys in North America. Other 

subgenera have been named in Eurasia (as Katamys and 

Tjanshanomys) but have been applied to only one species 

in most cases; they may merit subgeneric distinction. 

Discussion.-Von Koenigswald and Martin (1984a) 

recently have suggested that Mimomys never was present 

in North America. This opinion was based upon differences they described in the Schmelzmuster, the pattern of the enamel rods and its distribution within the 

enamel on the sides of the cheek teeth cusps. All other 

morphologic features and the history of dispersal of 

Mimomys throughout the Northern Hemisphere contradict this opinion (Hinton, 1932; Wilson, 1934; Wood 

and others, 1941; Stirton, 1951; Repenning and Fejfar, 

1977; Repenning, 1978; Repenning, 1980). In addition, 

the Schmelzmuster patterns examined by these authors 

were from some of the most endemically divergent species 

known from North America. The evidence of von 

4 Microtine Rodents, Hamilton Cave, West Virginia 

Koenigswald and Martin (l984a) is here considered 

inadequate. 

Subgenus CROMEROMYS, Zazhigin, 1980 

Dental diagnosis.-A subgenus of Mimomys with 

no enamel islet in anteroconid complex of m1 or posterior 

loop of M3, differing from subgenera Mimomys and 

Cseria and older species of subgenera Cosomys and 

Ophiomys; Mimomys Kante present in many individuals, 

tending to be anteriorly placed relative to other subgenera; dentine tracts very well developed on the 

anterobuccal side of the anteroconid cap and exceptionally elongate and parallel sided on both buccal and lingual 

salient angles of the posterior loop of m1 except in the 

oldest known form ( Cromeromys ex gr. intermedius of 

Zazhigin), differing from older species of other subgenera; m3 with completely confluent central triangles, 

more so than with other subgenera; M3 short with transversely wide posterior loop not exteJ).ded posteriorly 

[fig. 1B], not having the basined posterior loop of early 

forms of other subgenera but characteristic of later forms 

of the genus and differing from Borsodia; cement present in all known forms, tending to be very heavy in most, 

differing from the subgenera Mimomys and Cseria in its 

early development and from Borsodia and Hibbardomys 

and the subgenera Cosomys, Ophiomys, Ogmodontomys 

in its presence; m1 is 2.5 to 3.1 mm in length, averaging 

smaller than in the subgenera Mimomys, Cosomys, and 

Ogmodontomys. 

Included species.-Mimomys tornensis Janossy and 

van der Meulen, M. ex gr. intermedius of Zazhigin, M. 

irtyshensis Zazhigin, M. intermedius of Zazhigin; M. 

newtoni of Zazhigin, M. gansunicus Zheng, M. virginianus n. sp., and possibly M. monohani Martin [referred 

to the new genus Loupomys by von Koenigswald and 

Martin (1984a) on the basis of simplified Schmelzmuster, 

which has not been examined in the species of 

Cromeromys]. 

Discussion.-Zazhigin (1980) erected the genus 

Cromeromys, basing it on Cromeromys irtyshensis with 

the conception that Mimomys savini (=intermedius) and 

Mimomys newtoni should be included in it. However, at 

least some individuals of both M. savini and M. newtoni 

have an enamel islet with little wear. Repenning (in 

Repenning and others, 1987) agreed with the reality of 

Cromeromys because the characters of the genus (as 

defined) appeared very early in the history of the Arvicolini and carried well into the Pleistocene, apparently 

reflecting a discrete lineage. He also noted that some of 

the characters of Cromeromys were also characteristic of 

the genus Mimomys in North America (early loss of the 

islets and retention of the Mimomys Kante, but not the 

presence of cement). 

Repenning (in Repenning and others, 1987) failed 
to note, however, the inconsistency in retaining the 

similarly distinct North American forms within Mimomys 

as subgenera, while recognizing Cromeromys as a full 

genus. For this reason, a more balanced classification is 

used here and Cromeromys is considered a subgenus of 

Mimomys. 

Although Zazhigin's inclusion within Cromeromys 

of Mimomys savini and Mimomys newtoni (from the 

Cromerian of Europe, the source of his name) does not 

seem appropriate, at least one species of Cromeromys is 

present in Europe. This has been named Mimomys 

tornensis by Janossy and van der Meulen (1975). In the 

original description this species was described as being 

from the later Villanyian Osztramos-3 fauna of Hungary 

(the type locality) and from the early Biharian Kamyk 

fauna of Poland, where it occurs with Allophaiomys pliocaenicus. Therefore the temporal range of Cromeromys 

in central Europe is possibly 1 million years long, between 

1.5 and 2.5 million years ago. 

The subgenus has a longer time range in Asia; 

Zazhigin (1980) reported Cromeromys from the Beteke 

fauna of Kazakhstan (about 3.5 m.y. old) and from 

Tiraspolian faunas in the region of the Ob River valley 

(possibly as young as 850,000 years). A good evolutionary 

sequence of species is present during this time span, and 

this sequence is biostratigraphically useful. In China, 

Mimomys gansunicus Zheng belongs in this subgenus and 

Zheng and Li (1986) reported it from Nihewanian faunas 

(about 1.5 m.y. old). 

Prior to its discovery in Hamilton Cave, West 

Virginia, the sugenus Cromeromys was unknown in 

North America (with the possible exception of Mimomys 

monoham). The Cheetah Room faunal record appears 

to be slightly younger than other known records of 

Cromeromys. 

MIMOMYS (CROMEROMYS) VIRGINIANUS, new species 

(Figure lA-E) 

Holotype.-USNM 264308, a right first lower 

molar, little worn (fig. 1A). 

Type locality.-Cheetah Room, Hamilton Cave, 

Pendleton County, West Virginia; 0-50 em of floor 

deposits. 

Dental diagnosis.-A species of Mimomys 

( Cromeromys) similar to M. ( Cromeromys) tornensis 

J anossy and van der Meulen and to M. ( Cromeromys) 

irtyshensis Zazhigin except smaller; from M. (C.) tornensis it further differs in having less inflation of the cap 

of the anteroconid complex and in being less hypsodont. 

The first lower molar is about 2.5 mm long, smaller than 

other species, and all teeth have two roots, although the 

double-rooted ancestry is evident in the fused anterior 

roots of the upper second and third molars. 

Etymology.-Latin: masculine: "of Virginia." The 

species is named for its occurrence in the original State 

of Virginia and in reference to its eastern occurrence in 

the United States. 

Description and comparison.-Only eight teeth of 

this species have been found: three m1, two M3, two M2, 

and one M1; one M3 is questionably assigned (fig. 1C). 

Based upon this sample, individuals of the species are 

small; the recovered first lower molars measure 2.5, 2.5, 

and 2.4 mm in length of the occlusal surface, the type 

specimen being the smaller one. According to Janossy and 

van der Meulen (1975), Mimomys (Cromeromys) tomensis varies between 2.8 and 3.1 mm in this dimension. 

Zazhigin (1980) stated that Mimomys ( Cromeromys) irtyshensis measures 2.95 mm in the same dimension. Zheng 

and Li ( 1986) indicated that the m 1 of Mimomys 

(Cromeromys) gansunicus is 2.92 mm long; a referred 

specimen (F:AMNH 116248) from Nan Zhuang Gou, 

Yushe Basin, Shanxi Province, measures 3.1 mm, and 

three uncataloged mandibles in IVPP:AS recently collected in the Yushe Basin at field locality number YS-5 

measure 3.1, 3.1, and 2.6 mm in this dimension. 

The M3 of all forms (not known in M. gansunicus) 

is very similar except that of M. (C.) virginianus has a 

prominent dentine tract on the lingual salient angle of 

its anterior loop, rather than on the buccal one as in M. 

tornensis. The dentine tract in M. virginianus appears to 

be in the same position as in the M3 of Cromeromys irtyshensis figured by Zazhigin (1980, fig. 23-5). The M3 is 

similar to that of Phenacomys except for the dentine tract 

and the presence of cement (fig. 1B). 

The second M3 from the Cheetah Room fauna is 

questionably assigned as it has dentine tracts on both 

buccal and lingual salient angles of the anterior loop as 

well as one on the posterior face of the rather narrow 

and posteriorly extended posterior loop; this tooth has 

cement only in one reentrant, a situation believed 

abnormal. 

Discussion.-Aithough the subgenus Cromeromys 

is reported from both eastern and western Asia in deposits 

that may be only about 10,000 years older, the occurrence 

of Mimomys (Cromeromys) virginianus in a fauna so 

young and from the eastern United States is surprising. 

With the possible exception of Mimomys monohani, it 

is the only record of this subgenus in North America, 

although Phenacomys appears to be a derivative of this 

subgenus (Repenning and others, 1987). 

Genus PHENACOMYS, Merriam, 1889 

(Heather voles) 

Dental diagnosis.-Arvicolinine rodents differing 

from all other genera of the tribe by having a first lower 

molar with additional triangles in a notably variable 

Systematics 5 
0 

I I I I II 

X 

1mm 

I 

OCCLUSAL SCALE 

anteroconid complex, lingual alternating triangles and 

reentrants asymmetrically elongated; differing also from 

subgenus Mimomys (Mimomys) in that the Mimomys 

Kante is largely lost in the anteroconid of all but the most 

6 Microtine Rodents, Hamilton Cave, West Virginia 

0 1mm 

IIIII! I 

BUCCAL SCALE 

primitive species and enamel islets are never present; differs from subgenus Mimomys ( Cromeromys) in lack of 

cementum; last upper molar as in M. ( Cromeromys) 

except for the lack of cement. Progressively greater 
hypsodonty, elongation of dentine tracts, and complexity of anteroconid complex define subgenera. 

Included subgenera.-As discussed herein, the 

genus Phenacomys has three lineages in the living fauna, 

which are here grouped into the subgenera Phenacomys, 

Arborimus, and Paraphenacomys; the last is a new name 

(fig. 2). 

DIScussion.-Johnson (1973) has suggested that the 

differences between the living Phenacomys intermedius 

and Phenacomys longicaudus merit generic distinction 

and placed the latter in the genus Arborimus, Taylor. The 

dental distinction between Phenacomys intermedius and 

Arborimus longicaudus lies in the deeper fourth buccal 

reentrant (most anterior) on the occlusal surface of the 

first lower molar of Phenacomys. In Arborimus the 

posterior three buccal reentrants of m1 are usually of less 

uniform length below the occlusal surface than in 

Phenacomys intermedius, and the fourth (most anterior) 

is conspicuously less elongate; when only half worn the 

fourth buccal reentrant can be entirely lacking in Arborimus, whereas it is present in Phenacomys until the 

tooth crown is nearly worn away (fig. 3). 

In the fossil record as far back as 2 million years 

ago, these two variations are found as individual differences within single populations; polarization of the 

characters that separate Phenacomys from Arborimus 

took place less than 400,000 years ago (fig. 2). (See 

Repenning and others, 1987, under Phenacomys deeringensis; and Repenning, in press.) 

The teeth of the living species albipes resemble those 

of Phenacomys intermedius; and its tail length, in proportion to body length, is intermediate between Phenacomys 

intermedius and Arborimus longicaudus, as is its behavior. Phenacomys albipes is unique in the living fauna 

in that it has a shorter dentine tract on the buccal salient 

angle of the posterior loop of the first lower molar than 

either of the other two genera and their species. Although 

the species albipes has also been assigned to Arborimus 

(Maser and others, 1981), this shorter dentine tract 

Figure 1 (facing page). Dentition of Mimomys (Cromeromys) 

spp. Mimomys (Cromeromys) virginianus from the Cheetah 

Room fauna, Hamilton Cave, West Virginia. A, Holotype, right 

first lower molar in occlusal and buccal views, USNM 264308. 

x, Mimomys Kante. B, Right last upper molar in occlusal view, 

USNM 264309. C, Right last upper molar in occlusal view, questionably assigned, USNM 264310. D, Left first lower molar in 

occlusal and buccal views, USNM 264311. E, Left first lower 

molar in occlusal and buccal views, USNM 264312. Mimomys 

(Cromeromys) tornensis from the Osztramos-3 fauna, Hungary. 

F, Left first lower molar in buccal and occlusal views, HNHMB 

topotype. H-), Left first lower molars in occlusal views, 

HNHMB topotypes. Drawings of these specimens were provided by Old rich Fejfar. Mimomys (Cromeromys) tornensis from 

Kamyk fauna, Poland. G, Left first lower molar in buccal and 

occlusal views, USGS specimen. 

indicates that assignment of the species and lineage to 

either Phenacomys or Arborimus is inappropriate. 

In the fossil record longer dentine tracts on the 

buccal angle of the posterior loop of the first lower molar 

are evident 2.1 million years ago, in Phenacomys deeringensis. These longer dentine tracts break the enamel 

continuity on the occlusal surface before the tract on the 

buccal face of the anteroconid complex does, whereas in 

the living species Phenacomys albipes the tract on the 

posterior loop breaks the enamel pattern after the tract 

on the buccal face of the anteroconid complex (fig. 3). 

The past 2.4 million years have seen a gradual 

lengthening of the dentine tract of the posterior loop in 

the fossil record of the lineage leading toP. albipes, as 

opposed to an abrupt lengthening between P. gryci 

(2.4 m.y. ago) and P. deeringensis (2.1 m.y. ago) in the 

lineage leading to P. intermedius and Arborimus 

longicaudus (fig. 2). 

This indication of two lineages leading to the living species currently recognized as belonging to the genus 

Phenacomys, lineages that began more than 2 million 

years ago, is supported by the fauna from Locality 47 

in the Old Crow Basin, Yukon Territory, Canada, which 

has two forms of Phenacomys: a representative of 

Phenacomys deeringensis, with a long tract, and 

Phenacomys gryci, with a very short tract. The fauna 

from this locality is under study by R.E. Morlan and appears to be about 1. 7 million years old. These differences 

are shown in figure 3. 

Because of this history of diversification, it seems 

most appropriate to consider Arborimus, Taylor as a 

subgenus of Phenacomys, Merriam, rather than as a full 

genus, and to erect a third subgenus to include 

Phenacomys albipes. 

Subgenus PHENACOMYS, Merriam, 1889 

(Figure 3F, 3G) 

Dental diagnosiS.-A subgenus of Phenacomys 

with buccal dentine tract on the posterior loop of the first 

lower molar longer than that on the buccal face of the 

anteroconid complex, differing from Subgenus 

Paraphenacomys, new name; and, in forms younger than 

about 400,000 years, fourth buccal reentrant ·of the same 

tooth deep in occlusal view and nearly as long in buccal 

view as the posterior three, differing from Subgenus 

Arborimus. 

Included species.-Phenacomys deeringensis (2.1 

to 1.7 m.y. old) and P. intermedius (living). There are 

at least three unnamed species older than the approximately 400,000-year-old polarization of characters that 

led to Arborimus. 

DIScussion.-As mentioned, polarization of characters that now separate the subgenera Phenacomys and 

Systematics 7 
W OTHER 

~ DERIVED MIMOMYS 

~a GENERA (PARAPHENACOMYS) 

0 

1 

<C 

_, 

0 

0 

> 0: 

<C 

-f/l 

Living - P. albipes 

Nevada- P. albipes 

W.Va. - P. sp. 

PHENACOMYS 

(PHENACOMYS) (ARBORIMUS) 

Living- P. intermedius jliving- P. longicaudus Nevada- P. longicaudus 

-----------~---- Ida. - P. n. sp. \.!) 

2 

> 

:1 

0 

:1 

:1 

- Yukon Ter. - P. gryci Yukon Ter. -P. deeringensis 

Alaska- P. deeringensis 

f/l 

> --------------~ :1 1 Alaska and Yakutia - P. gryci 

3 

0 fll I 

: ~ r-® 0 l 

:1 I 

:1 : 

G}: 4 L----' 

I ___ _j (D- Cementum developed on cheek teeth 

® - Short dentine tract 

5 ®- Long dentine tract 

MIMOMYS @)-Weak 4th buccal reentrant 

Figure 2. Inferred phylogeny of the Phenacomys lineage. 

Arborimus can be traced back less than 400,000 years ago 

(younger than the Booth Canyon fauna of eastern Idaho, 

unpublished, Idaho State Museum locality; see Repenning, in press). Those older fossil forms, as old as the 

2.1 million-year-old Phenacomys deeringensis, that have 

these characters as individual morphologic variants are 

also included in this subgenus. The subgenus is known 

only in North America from 2.1 million years ago to the 

present. 

Subgenus ARBORIMUS, •raylor, 1915 

(Figure 3H) 

Dental diagnosis.-A subgenus of Phenacomys 

with buccal dentine tract on the posterior loop of the first 

lower molar longer than that on the buccal face of the 

anteroconid complex, differing from the Subgenus 

Paraphenacomys, new name; and fourth buccal reentrant 

of the same tooth shallow in occlusal view and much 

shorter in buccal view than the second buccal reentrant, 

differing from Subgenus Phenacomys. 

8 Microtine Rodents, Hamilton Cave, West Virginia 

Included species .-Phenacomys longicaudus and 

Phenacomys n. sp. (Johnson and George, in press). No 

fossil species have been recognized or named. 

Discussion.-The subgenus is known only from the 

western conterminous United States. At present only one 

possible fossil record of Phenacomys (Arborimus) 

longicaudus is known: AMNH 301:6678 from the 6,000 

year-old Gatecliff Shelter, Nye County, Nevada 

(Grayson, 1983; Repenning, in press). 

Subgenus PARAPHENACOMYS, new name 

(Figure 3A -E) 

Dental diagnosis.-A subgenus of Phenacomys 

with relatively low crowned cheek teeth and buccal dentine tract on the posterior loop of the first lower molar 

shorter than that on the buccal face of the anteroconid 

complex, differing from other subgenera. 

Etymology.-Greek: masculine: "near Phenacomys.'' The subgenus is named for its close relationship 

with the subgenus Phenacomys. 
A B 

G 

Figure 3. First lower molars of Phenacomys. x, fourth buccal 

reentrant; y, Dentine tract in buccal salient angle of posterior 

loop. A, Phenacomys (Paraphenacomys) gryci from the Fish 

Creek fauna, North Slope, Alaska, USNM 264317, age 2.4 m.y. 

8, P. (Paraphenacomys) brachyodus from the Cheetah Room 

fauna, West Virginia, Holotype, USNM 264319, age about 

800,000 years. C, P. (Paraphenacomys) brachyodus from the 

Cheetah Room fauna, West Virginia, USNM 264318. 0, P. 

(Paraphenacomys) albipes from the Smith Creek Canyon Fauna, 

Type species.-Phenacomys albipes Merriam, 

1901. 

Included species.-Phenacomys albipes, P. brachyodus n. sp., and P. gryci. 

Discussion.-The subgenus is known in North 

America from 2.4 million years ago to the present and 

presumably is also known in Beringian Asia 2.4 million 

years ago (Repenning and others, 1987). 

c 

0 2 mm 

'""' I I BUCCAL SCALE 

0 2 mm 

I II II I I 

OCCLUSAL SCALE 

Nevada, Univ. Arizona uncataloged specimen, age about 

13,000 years. E, P. (Paraphenacomys) albipes from Benton 

County, Oregon, Burke Museum 34501, modern. F, P. 

(Phenacomys) deeringensis from Cape Deceit fauna, Seward 

Peninsula, Alaska, Univ. Alaska 636, age 2.1 m.y. G, P. 

(Phenacomys) intermedius from Glacier National Park, 

Montana, USGS 6824, modern. H, P. (Arborimus) longicaudus 

from Tillamook County, Oregon, Burke Museum 34492, 

modern. 

In the living fauna Phenacomys (Paraphenacomys) 

albipes is restricted to the coastal forests of Oregon and 

northernmost California; today it is a rare species. It is 

known from one fossil record, uncataloged first lower 

molar in the University of Arizona from the 

± 13,000-year-old Smith Creek Cave fauna, White Pine 

County, Nevada (Mead and others, 1982; Repenning, in 

press). 

Systematics 9 
PHENACOMYS (PARAPHENACOMYS) BRACHYODUS, 

new species 

(Figure 3B, 3C) 

Holotype.-USNM 264319, a left first lower molar, 

little worn (fig. 3B). 

Type locality.-Cheetah Room, Hamilton Cave, 

Pendleton County, West Virginia. 0-50 em of floor 

deposits. 

Dental diagnosis.-A species of the subgenus 

Paraphenacomys differing from P. (Parqphenacomys) 

gryci in having a more elongate buccal dentine tract on 

the posterior loop of m1 and better developed additional 

wings on the anteroconid complex of the first lower 

molar; differing from P. (Paraphenacomys) albipes in 

having a shorter buccal dentine tract on the posterior 

loop. First lower molar is about 2.5 mm long, shorter 

than most other species of the genus but within the range 

of variation of some. 

Etymology.-Greek: masculine: "short tooth." In 

reference to the low crowned cheek teeth and short buccal 

dentine tract on the posterior loop of the first lower 

molar. 

Description and comparison.-Six cheek teeth, including two m1, of Phenacomys brachyodus are in the 

microtine sample from the Cheetah Room fauna. The two 

first lower molars are small (occlusal lengths are 2.45 and 

2.50 mm) and, when compared with modern specimens 

of equal root development, the two fossil mls appear 

lower crowned; this apparent lower crown is paralleled 

by remarkably short dentine tracts on the buccal salient 

angle of the posterior loop of the first lower molar 

(fig. 3B, 3C). 

No species of the subgenera Phenacomys or Arborimus has a dentine tract on the buccal salient angle 

of the posterior loop of the first lower molar that is as 

short as that on the two first lower molars from the 

Cheetah Room fauna. In addition, the few known 

specimens of the subgenus Paraphenacomys that are 

younger than the Cheetah Room fauna, including the living P. albipes, do not have as short a dentine tract, suggesting progressive evolution of the feature. Only the 

oldest known species, Phenacomys (Paraphenacomys) 

gryci, has a shorter tract on the posterior loop than do 

the specimens from the Cheetah Room fauna. 

The late Pliocene species Phenacomys 

(Phenacomys) deeringensis (Guthrie and Matthews, 1971) 

has much more elongate dentine tracts on this angle of 

this tooth; they break the enamel pattern of the occlusal 

surface before wear intersects the dentine tract on the 

buccal face of the anteroconid complex (fig. 3F). 

Development of the dentine tracts is a universally 

recognized taxonomic criterion in the microtine rodents, 

and in Phenacomys differences in this development clearly indicate the existence of two lineages that derive from 

10 Microtine Rodents, Hamilton Cave, West Virginia 

ancestral Phenacomys gryci. Subgenus Paraphenacomys 

is characterized by relatively slow development of the 

dentine tract on the buccal side of the posterior loop of 

the first lower molar; Subgenera Phenacomys and Arborimus are characterized by early and rapid development 

of this tract to the condition in which it is more elongate 

than the tract on the buccal face of the anteroconid complex of the first lower molar. The presence of two forms 

of Phenacomys (R.E. Morlan, writen commun., 1986) 

from the presumed 1. 7 million-year-old Locality 47, Old 

Crow Basin of Yukon Territory, one form being P. deeringensis with elongate tract and the other P. gryci with 

very short tract, supports the concept of two contemporaneous lineages. 

The Paraphenacomys lineage includes all forms 

derived from the ancestral Phenacomys gryci in which 

the dentine tract on the buccal face of the anteroconid 

complex interrupts the enamel pattern of the occlusal surface before the buccal tract of the posterior loop does 

so. Not many examples are known, although many fossil 

records have not been examined for this character. Those 

known are shown in figure 3; they include Phenacomys 

gryci from northern Alaska and Yukon Territory (2.4-1. 7 

m.y. old), Phenacomys brachyodus from the Cheetah 

Room fauna (ca. 0.8 m.y. old), P. albipes from the Smith 

Creek Cave fauna, Nevada (Repenning, in press; ca. 

0.013 m.y. old), and livingP. albipes from coastal Oregon 

and northern California. 

The presence of Phenacomys (Paraphenacomys) 

brachyodus in the Cheetah Room fauna indicates a 

former distribution to the Atlantic coast, possibly only 

in Canada during interglacial periods, that would seem 

comparable to the modern distribution of Phenacomys 

(Phenacomys) intermedius. The environmental factors 

that caused its present restriction to the wet Pacific 

hemlock and coastal Douglas fir forests of western 

Oregon are unknown but fascinating. It should be noted 

that the 13,000-year-old record from Smith Creek Cave 

in easternmost Nevada is associated with dry subalpine 

Douglas fir forests (Mead and others, 1982) and that the 

present limited range may reflect some change in habit 

as well as environment (Repenning, in press). 

Genus ALLOPHAIOMYS, Kormos, 1932 

Dental diagnosis.-Arvicolinine rodents differing 

from all other genera except Arvicola in having rootless 

cheek teeth; as in Arvico/a anteroconid complex of m1 

consists of a simple trefoil with prominent primary wings 

and a more or less globular cap frequently skewed lingually; prominent dentine tracts on the anterobuccal face of 

the cap of the anteroconid complex and on both buccal 

and lingual salient angles of the posterior loop; M3 simple, lacking a fully developed third alternating triangle, 

posterior loop usually extended to the rear, and dentine 
tracts on both buccal and lingual salient angles of the 

anterior loop and on the posterior surface of the posterior 

loop; teeth well cemented; mean length of m1 less than 

3.0 mm, differing from Arvicola. 

Discussion.-AIIophaiomys and Arvicola are very 

similar because both are basically Mimomys without roots 

on their cheek teeth. Even their Schmelzmuster is essentially the same and is comparable to that of Mimomys 

(von Koenigswald, 1980). In Allophaiomys the lingual 

and buccal reentrants anterior to the primary wings of 

the anteroconid complex tend to be more nearly of equal 

size than in Arvicola, the posterior loop of the last upper molar usually is more elongate posteriorly, the buccal 

reentrants and the second alternating triangle of m3 tend 

to be more weakly formed, and the cement in the reentrants of the teeth usually is more heavily deposited than 

in Arvicola; but the two genera are difficult to separate. 

The most consistent difference is the mean length of the 

first lower molar of Arvicola, which is greater than 

3.0 mm. The two genera are almost temporally exclusive 

of each other; Allophaiomys is known from perhaps 2.5 

million years ago in Asia until about 450,000 years ago 

in Europe and North America (excepting its living relic, 

Phaiomys, of the Himalayas and the Tibetan Plateau). 

In contrast, populations referred to Arvicola appear to 

evolve out of Mimomys savini, by the loss of roots on 

the cheek teeth, no earlier than about 500,000 years ago. 

Except for large size, there is absolutely no morphologic similarity between the teeth of Arvicola and 

Microtus richardsoni of North America, which is 

sometimes considered closely related to Arvicola (Hall, 

1981). Microtus richardsoni may be a late Pleistocene 

North American derivative of Microtus xanthognathus, 

based upon the similarity of their teeth, and certain1y is 

not phylogenetically close to Arvicola of Eurasia, which 

has very different teeth. 

It has been almost universally recognized that both 

Pitymys and Microtus evolved from Allophaiomys (Kretzoi, 1969; Chaline, 1974; van der Meulen, 1978, fig. 15; 

Repenning, 1983; and possibly Martin, 1987). This has 

led to a problem in classification. 

It has been assumed, without discussion, that 

Allophaiomys cannot be grouped with Mimomys because 

it has no roots on its teeth. However, if Pitymys and 

Microtus are grouped separately, there is an equal problem deciding into which group Allophaiomys should be 

placed. No one has suggested that a separate tribe be 

erected for this single genus (or generic pair). Solutions 

have been either to place Al/ophaiomys (and Phaiomys) 

in the Pitymys group, or to put all forms concerned under 

the single genus Microtus. The first is incorrect as it does 

not allow for the derivation of Microtus from 

Allophaiomys; and the second seems to only lower the 

dilemma in rank until it is not prominent. The second 

also requires that an author either use the trinomial name 

throughout the discussion, or slip back into speaking of 

the subgenera of Microtus (Allophaiomys, Pitymys, 

Microtus, etc.) as though they were genera (van der 

Meulen, 1978, for example); this confuses the reader, and 

perhaps sometimes the writer as well. 

As here classified, Allophaiomys is considered a 

genus of the Tribe Arvicolini that has no roots on its 

cheek teeth and Pitymys and Microtus are thus allowed 

to be classified as the separate lineages that they are. 

ALLOPHAIOMYS PLIOCAENICUS Kormos, 1933 

Dental diagnosis.-A species of Allophaiomys with 

average width of the commissure between primary wings 

and cap of anteroconid complex of m1 slightly narrower, 

and average length of anteroconid complex (relative to 

the posterior part of the tooth) slightly longer than in the 

only other defined species, Allophaiomys deucalion Kretzoi [see van der Meulen, 1974, for discussion]. 

Discussion.-Thirty first lower molars of 

Allophaiomys pliocaenicus are in the collection from the 

Cheetah Room fauna. These were compared with 10 from 

the Kentuck fauna of Kansas, 13 from the Wathena fauna 

of Kansas, 9 from the Java fauna of South Dakota, a 

single large individual from the Aries fauna of Kansas, 

1 from the Hanover Quarry fauna of Pennsylvania, 2 

from the Wellsch Valley fauna of Saskatchewan, and 4 

from Kamyk, Poland. 

Particular attention was paid to the criteria of van 

der Meulen (1978) in his definition of Allophaiomys 

guildayi from Cumberland Cave, Maryland (defined as 

Microtus (Pedomys) guildayz). It was obvious that individual variation in the species represented in the 

Cheetah Room fauna overlapped the typical morphology 

of Allophaiomys guildayi, but the majority of individuals 

did not conform to it. The teeth from the Cheetah Room 

fauna averaged 10 percent smaller than the four Polish 

specimens compared, but the size range of all population 

samples compared was great. 

It was a matter of prudent nomenclature in 1975 

when R.A. Martin pointed out that specimens from the 

United States were very similar to the form called 

Allophaiomys p/iocaenicus in Europe and referred them 

to "AIIophaiomys sp. cf. A. pliocaenicus Kormos." In 

the 13 years that have since passed, many additional 

localities and specimens have been found and no one has 

been able to satisfactorily demonstrafe a difference. This 

seems reason enough to assign the North American fossils 

to the Eurasian species until it can be established that they 

differ from it. 

Tribe MICROTINI, Simpson, 1945 

Dental diagnosis. -Arvicoline rodents with rootless 

cheek teeth; differing from the Pitymyini in having 

Systematics 11 
anteroconid complex on m 1 with at least the buccal 

primary wing of Allophaiomys developed into an additional triangle (alternating triangle 4) by being pinched 

off through elongation of the third lingual reentrant that 

meets the enamel wall of the third buccal reentrant [fig. 

4]; M3 primitively "simple," like that found in living 

North American species of Pitymys and fossil species of 

Allophaiomys [figs. 4D, 40], having only two buccal and 

two lingual cement-filled reentrants; M3 of derived morphotypes "complex" with three cement-filled reentrants 

on buccal and lingual sides (in North America, all included in Microtus) [fig. 4.1]; most anterior buccal reentrant of M3 not reduced and about opposite most anterior 

lingual reentrant, differing from the Lagurini. 

Included genera.-Lasiopodomys, Microtus, and 

Proedromys. 

Discussion.-These three genera are considered as 

subgenera of Microtus by neo-mammalogists and are 

separated here because they can be separately diagnosed 

from their dentition. Although not all are represented in 

the Cheetah Room fauna, they are here diagnosed, 

discussed, and illustrated in figure 4, in explanation of 

the nomenclature used. 

There are many additional subgenera within 

Microtus that are not here separated because the history 

of their development is not known, but it is expected that 

they will be separately diagnosed according to this history 

when it is known. Even in the strict sense here used, the 

genus Microtus is very large. 

Genus PROEDROMYS, Thomas, 1911 

(Bedford's vole, figure 4A) 

Dental diagnosis.-Microtinine rodents with 

anteroconid complex of m1 having one additional triangle 

and no trace of a secondary lingual wing on its cap 

[marked x on fig. 4], differing from all other genera of 

the tribe except those fossils that are included in 

Lasiopodomys; M3 reduced, differing from other genera 

of the tribe, and all other microtines [fig. 4A]. 

Discussion.-This genus is known only from 

China, both living and fossil, but retains a very primitive 

m1 that differs from that of Allophaiomys only in the 

closing of the buccal primary wing of the anteroconid 

complex (fig. 4A). It is unique in its loss of the posterior 

parts of M3 when compared with that tooth of 

Allophaiomys (compare fig. 4A with 4G), but it is 

remarkable in the similarity of its m1 to that of fossil 

species here included in the genus Lasiopodomys, including the species from the Cheetah Room fauna. Zheng 

and Li (in press) reported Proedromys cf. bedfordi from 

the Gongwangling fauna, Shaanxi, between 740,000 and 

1 million years old, and they reported the living species 

in more recent faunas. The genus is monospecific. 

12 Microtine Rodents, Hamilton Cave, West Virginia 

Genus LASIOPODOMYS, Lataste, 1887 

(Transbaikalian vole) 

Dental diagnosis.-Microtinine rodents with 

anteroconid complex of m1 having one or two additional 

triangles, and differing from Microtus in having no trace 

of a secondary lingual wing in older forms or only a very 

weak secondary lingual wing in some late Pleistocene and 

living individuals; M3 neither reduced nor complicated, 

remaining as in Allophaiomys, and differing from Proedromys in its lack of reduction and from Microtus in 

its lack of later complication [fig. 4B-4D, 4F, and 40]. 

Included species.-Lasiopodomys brandti, L. 

brandtoides, L. deceitensis, and L. praebrandti. 

Discussion.-Repenning (1980 and later) has suggested that one North American fossil species with a 

simple M3, like that in Allophaiomys, and with no 

secondary wings on the anteroconid cap of m1, as in 

Allophaiomys and Proedromys, might better be assigned 

to this genus, rather than to Microtus. Although another 

fossil locality has been found in North America containing this species (Locality 47, Old Crow Basin, Yukon Territory, Canada), little has been discovered that supports 

the suggestion. 

The difficulty in defending the generic assignment 

lies in the lack (except for the Chinese fossil Lasiopodomys brandtoides) of a record of forms intermediate 

Figure 4 (facing page). First lower molars of Trib~ Micro~ini. 

Features of the anteroconid complex: x, secondary lingual w1ng; 

y, first additional triangle; z, second additio~al triangle (or 

secondary buccal wing); cap, cap of anterocomd ~omplex .. A, 

Proedromys sp. cf. P. bedfordi from Gongwangllng locality, 

Shaanxi, China, IVPP:AS specimens: right first lower and left 

last upper molars; this is a reduced M3, compare with G. Drawings of these specimens were provided by ~heng Shaohua an? 

Li Chuankuei. 8, Lasiopodomys praebrandt1 from Kudun locality, Transbaikalia, ZZSD:PAN:~ M~1551-76: right fir~t lower 

molar. C, Lasiopodomys dece1tens1s from Cape Dece1t fauna, 

Alaska: right first lower molar, UA 418, and right last upper 

molar, little worn, UA 244, a "simple" morphotype comparable 

to that in 0. 0, F, and G, Lasiopodomys deceitensis from 

Cheetah Room fauna, West Virginia. 0, Associated right first 

lower and right last upper molar, USNM 264316; a "simple" 

morphotype, but if cement were present in the posterolingual 

reentrant it would be "intermediate"; F, Right first lower molar, 

USNM 264319; G, Left last upper molar, USNM 264318, also 

a "simple" morphotype. E, Microtus paroperarius from the 

Cheetah Room fauna: left first lower molar, USNM 264317; 

note weak lingual and buccal secondary wings, comparable 

to K. H, I,}, M. paroperarius from the Sunbrite Ash Pit, Kansas, USGS specimens. H, Left first lower molar with strong 

lingual secondary wing; I, Right first lower molar with moderate 

lingual and buccal secondary wings;}, Right last upper molar; 

this is a "complex" morphotype. K, M. paroperarius from 

Locality CT2 of the Hansen Bluff fauna~ sequ~nce, Co~orado, 

UC specimen of a large-sized population; th1s tooth IS from 

associated upper and lower dentitions and the individual had 

a "simple" M3 similar to 0. 
B 

y 

G 

cap 

0 1mm 

Ill I I I I 

Systematics 13 
between these presumed early forms of Lasiopodomys 

and the living form, Lasiopodomys brandti, which has 

somewhat more complicated first lower molars. The living species, from western Transbaikalia, usually has the 

second additional triangle fully closed as well as a very 

weak secon<~;ary lingual wing in some individuals; it is 

known in the fossil record of Siberia and China for the 

last million years. 

Erbaeva (1976) named Lasiopodomys praebrandti 

(fig. 4B) from the Kudun fauna south of Lake Baikal 

(about 2 million years old) and attempted to trace the 

history of the genus to the living species; her record had 

a gap between the latest Pliocene and the beginning of 

late Pleistocene, a gap comparable in time with that 

known in North America. In Transbaikalia this time gap 

covers the transition between the earlier L. praebrandti, 

with ''almost'' one additional triangle in the anteroconid 

complex (fig. 4B) to that of the living form, having two 

clear cut and fully closed additional triangles. In North 

America no specimen is known with a fully closed second 

additional triangle, although the first is fully closed in 

Lasiopodomys deceitensis. Microtus oregoni has a welldeveloped secondary lingual wing and therefore qualifies 

as a species of Microtus, although it has a "simple" M3. 

In addition, Erbaeva (oral commun., 1982) has 

subsequently decided that her species probably belongs 

in Allophaiomys because the constriction in the enamel 

pattern never quite closes off the first additional triangle 

of the anteroconid complex. However, in her sample the 

prevalence of a distinct narrowing of the commissure between this incomplete triangle ·and the cap of the 

anteroconid complex at least suggests that it is a species 

of Allophaiomys that was evolving toward the Microtini. 

The use of this genus is primarily defended by the 

persistent "simple" last upper molar and the lack of a 

well-developed secondary lingual wing on the anteroconid 

cap of the first lower molar (marked x on fig. 4). 

LASIOPODOMYS DECEITENSIS (Guthrie 

and Matthews, 1971) 

(Figure 4C, 4D, 4F, and 4G) 

Dental diagnosis.-A species of Lasiopodomys 

with the first additional triangle of anteroconid complex 

of m1 completely closed, differing from Lasiopodomys 

praebrandti; commissure between the cap of complex and 

second additional triangle broadly confluent, differing 

from Lasiopodomys brandti; no well-developed secondary lingual wing of the anteroconid complex cap, differing from Microtus. Length of m1 about 2.8 mm, larger 

than L. praebrandti. 

Discussion.-The resemblance of the m1 in this 

species to that of Proedromys is remarkable (fig. 4A, 4C, 

4D, and 4.F), but the distinctly reduced M3 of the Chinese 

genus is not found with the North American forms. 

Eighty rootless third upper molars were in the collection 

14 Microtine Rodents, Hamilton Cave, West Virginia 

from the Cheetah Room fauna. They were sorted by 

degrees of complication: "simple" with two lingual and 

two buccal cement-filled reentrants (fig. 4D and 4G); "intermediate" with three lingual and two buccal cementfilled reentrants (fig. 4D if the posterior lingual reentrant 

contained cement); and "complex" with three buccal and 

three lingual cement-filled reentrants (fig. 4.1). Sixty-nine 

last upper molars were "simple" and could belong to 

Pitymys, Allophaiomys, or Lasiopodomys in the fauna. 

Seven were "intermediate" and could belong to Pitymys, 

Allophaiomys, Lasiopodomys, or Microtus. Four were 

"complex" and, in North America, could only belong to 

Microtus. In Eurasia they could also belong to Pitymys 

or Neodon. 

In the Cheetah Room fauna there are 31 first lower 

molars assigned to Lasiopodomys deceitensis, 52 that are 

assigned to Pitymys hibbardi, 30 assigned to Allophaiomys pliocaenicus, and only 8 that are believed to be 

assignable to Microtus paroperarius. From these proportions it would seem that about 20 of the last upper molars 

belong to Lasiopodomys deceitensis; they could be either 

"simple" or "intermediate" in form. There is only one 

associated dentition in the microtines of the Cheetah 

Room fauna and it is of Lasiopodomys deceitensis (fig. 

4D). It almost has an "intermediate" last upper molar, 

but this does not differ from those of the type population from Alaska (fig. 4C). 

Lasiopodomys deceitensis was described (as 

Microtus deceitensis) from the Cape Deceit fauna of the 

Seward Peninsula, Alaska (Guthrie and Matthews, 1971). 

This fauna is about 2.1 million years old by a variety of 

lines of correlation (Repenning and others, 1987). The 

species is also known from the unpublished Locality 47 

of the Old Crow Basin, Yukon Territory, Canada, which 

is under study by R.E. Morlan and which is believed to 

have been deposited during the Olduvai event (Repenning 

and others, 1987). The presence of the species in the much 

younger Cheetah Room fauna may require reevaluation 

of the age interpretation of Locality 47; the normal polarity determination of the sediments could represent the 

Jaramillo event, rather than the Olduvai event, as has been 

inferred. If so, there are three other unusually late records 

of microtine rodents in the fauna. 

As mentioned, assignment of this species to the 

genus Lasiopodomys is based upon the assumption that 

the retention of a primitive M3 and the lack or virtual 

lack of a secondary lingual wing on the anteroconid cap 

of m1 define a single lineage. This assumption remains 

untested because there is a genuine (and unusual) "missing link" in the fossil record. 

Genus MICRarUS, Schrank, 1798 

(Meadow mice) 

Dental diagnosis.-Microtinine rodents differing 

from Proedromys and Lasiopodomys in having an 
anteroconid complex of ml with a secondary lingual wing 

[marked x on fig. 4] developed on the cap, secondary buccal wing variably present; M3 may be "simple" in early 

fossil forms, but is universally "complex" in younger fossil 

and living forms. Two or more additional triangles formed 

from the primary wings (a total of five or more alternating 

triangles) on ml of many forms, differing from Proedromys and early Lasiopodomys; the second additional 

(fifth alternating) triangle is the lingual primary wing of 

the anteroconid in Allophaiomys and Proedromys but is 

not completely, or is variably, closed off from the cap of 

the anteroconid complex cap in several forms. The "simple" M3 of Microtus oregoni is an exception, as noted by 

Repenning (1983), and the Central American Herpetomys 

and Orithriomys are not understood. 

Included species.-Microtus paroperarius and 

many more advanced species. 

Discussion.-Much remains unknown about the 

phylogenetic patterns of the various species of fossil and 

living Microtus. R.A. Martin (1987, p. 273) stated: "a 

classification should at its best be a hypothesis regarding 

the relationships of monophyletic groups.'' In agreement 

with this, there seems to be little point in altering the existing classification until firm evidence clarifies it. 

However, it is recognized that the genus potentially contains several subgenera that could be elevated to generic 

status once their diversification is understood. 

The oldest known species in the United States east 

of the Rocky Mountains is Microtus paroperarius Hibbard. This species and at least two others are known from 

the much older Locality 47 in the Old Crow Basin, Yukon 

Territory, and are under study by R.E. Morlan. This 

species is also known from the much older Wellsch Valley 

fauna, Saskatchewan, and is under study by C.S. 

Churcher. A fairly large variety of species between 1 and 

2 million years old has been recognized in northern 

Eurasia. 

MICROTUS PAROPERARIUS Hibbard, 1944 

(Figure 4E and 4H-4K) 

Dental diagnosis.-A species of Microtus morphologically close to the living Microtus oeconomus 

[ =M. operarius Nelson of Hibbard, 1944] in structure 

of m1 but differing in that cap of anteroconid complex 

is less inflated and reentrant anterior to secondary lingual 

wing less developed. Differing from many other species 

in that second additional triangle is prominent but still 

broadly confluent with cap; lingual secondary wing 

[marked x on fig. 4] usually less prominent than in M. 

oeconomus because of weak reentrant anterior to it; M3 

"simple" [as fig. 4D and 4G] in forms older than about 

850,000 years and "complex" [fig. 4.1] in those younger 

than about 610,000 years. Size variable and length of M1 

ranges from 3.6 mm [Loc. CT2, Hansen Bluff fauna, 

Colorado, fig. 4K] to 2.15 mm [Alfred Shoemaker loc., 

Nebraska, mentioned by Paulson, 1961; see also van der 

Meulen, 1978, table 3]. 

Discussion.-The oldest prior records in the United 

States of Microtus paroperarius are from Hansen Bluff, 

Colorado, and are about 820,000 years (Rogers and 

others, 1985). At Locality CT2 in the base of the Hansen 

Bluff faunal succession, the only associated upper and 

lower dentition of Microtus paroperarius known to us has 

a "simple" third upper molar (like fig. 4D; it is from the 

specimen whose m1 is shown in fig. 4K}. However, of 

20 last upper molars from four closely spaced localities 

in the lower part of the Hansen Bluff succession 

(Localities CT1, CT2, CT3, and PP2), only 8 (40 percent) were of this "simple" morphotype, and these could 

belong to either Pitymys or Microtus in the fauna; the 

remaining 60 percent were of the "complex" morphotype 

(similar to fig. 4.1) and had to belong to Microtus. Thus, 

more than 60 percent of the individuals of Microtus 

paroperarius from the 820,000-year-old level in the 

Hansen Bluff faunal sequence had a "complex" last 

upper molar. 

All last upper molars from the type Cudahy population and the referred Sunbrite Ash Pit locality, Kansas, 

appear to have the "complex" M3, although one cannot 

be certain because the associated Pitymys meadensis introduced "simple" M3s into the fossil sample; these are 

about 610,000 years old. 

At Locality 47 in the Old Crow Basin of Yukon 

Territory (under study by R.E. Morlan) and in the 

Wellsch Valley fauna of Saskatchewan (under study by 

C.S. Churcher), first lower molars assignable to Microtus 

paroperarius are found with "simple" last upper molars. 

However, "complex" M3s occur in Locality 47 and at 

least two other species of Microtus are present; the 

disposition of the last upper molars to species from 

Locality 47 is still uncertain. These two faunas seem to 

have been deposited during the Olduvai Normal Polarity Subchron (1.89-1.67 m.y. old). 

Microtus paroperarius appears to represent a 

monophyletic lineage that shows progressive evolution in 

the morphology of M3 over a known time period extending from about 1.8 million years ago until about 400,000 

years ago. Its extinction in the United States appears to 

have occurred shortly following the invasion of Microtus 

pennsylvanicus. 

Identification of Microtus paroperarius in the 

Cheetah Room fauna is tenuous. The eight first lower 

molars assigned to this species are difficult to separate 

from Lasiopodomys deceitensis; figure 4£ shows the first 

lower molar that is most obviously assignable to M. 

paroperarius because its development of a secondary 

lingual wing on the anteroconid complex (marked x on 

the figure) is strongest. 

Systematics 15 
Only the presence of four "complex" M3s (discussed under Lasiopodomys deceitensis) certainly indicates that some specimens present must represent 

Microtus, as here restricted. It is on the strength of these 

four last upper molars that the eight m1s with weak secondary lingual wings have been removed from the sample 

of m1s assigned to Lasiopodomys. Without the "complex'' last upper molars, these first lower molars assigned 

to Microtus paroperarius would have been included in 

Lasiopodomys deceitensis and would have been considered as advanced individuals (the "missing link") 

trending toward the living L. brandti, and as supporting 

the generic assignment. 

It would appear that the Cheetah Room fauna lived 

sometime between 850,000 years ago, when Microtus 

paroperarius entered the United States (Repenning, 1984), 

and considerably before 610,000 years ago, when the 

species had evolved a "complex" last upper molar in 

essentially all of its population and a much more pronounced lingual secondary wing on the anteroconid cap 

of its first lower molar. The development of secondary 

wings in the Cheetah Room fauna more closely resembles 

the condition found in the 820,000-year-old sample from 

Hansen Bluff (fig. 4K) than those from the 610,000-yearold type sample from the Cudahy fauna (fig. 4H and 41), 

suggesting a more similar age, and the rarity of "complex" M3s in the fauna from West Virginia suggests an 

even older age. 

Tribe PITYMYINI, Repenning, 1983 

Dental diagnosis.-Arvicoline rodents with rootless 

cheek teeth and an anteroconid complex on m 1 with one 

or more pairs of additional triangles-the first pair 

(triangles 4 and 5) approximately opposing, differing 

from the Microtini; development of further additional 

triangles also occurs as opposing pairs; M3 "simple" with 

only two cement-filled reentrants on both buccal and 

lingual sides in North America, differing from advanced 

Microtus, but may be "complex" in Eurasia. Basic pattern of the configuration of cap varies with species. 

Included genera.-Neodon, Pitymys, and Tyrrhenicola, questionably also Herpetomys and Orithriomys. 

Discussion.-There are two known specimens, both 

of Pitymys quasiater, that contradict the extremely simple M3 in North American Pitymys; KU-19876 (Repenning, 1983) and KU-24465 (Martin, 1987), both from 

Veracruz, Mexico. The M3s on these specimens are 

''complex,'' but the vast majority of individuals of this 

species have an M3 that conforms to the diagnosis. It 

would appear that the species group including P. 

quasiater (Repenning, 1983), derived from immigrants 

from Eurasia, is evolving a "complex" M3 as did those 

in Eurasia at an earlier date. 

In North America the tribe Pitymyini includes the 

16 Microtine Rodents, Hamilton Cave, West Virginia 

genus Pitymys. In the Old World the tribe includes 

Neodon, Pitymys, and Tyrrhenicola. Possibly also to be 

included in North America are the Central American 

forms Orithriomys umbrosus, which has a very primitive 

m1 and a "simple" M3 like those of Allophaiomys (it 

may represent a southern holdover comparable to 

Phaiomys in Asia), and Herpetomys guataemalensis, 

which has an advanced, Pitymys-like ml but a "complex" M3 (like a few individuals of Pitymys quasiater 

from central Mexico). 

Genus PITYMYS, McMurtrie, 1831 

(Pine voles) 

Dental diagnosis.-Pitymyinine rodents with "simple'' M3. Two individuals of Pitymys quasiater that are 

exceptions have been noted above. 

Included species.-Pitymys aratai, P. cumberlandensis, P. hibbardi, P. mcknowni, P. meadensis, P. 

nemoralis, P. ochrogaster, P~ pinetorum, and P. 

quasiater, in North America. Corbet (1978) listed 15 

species in Eurasia, several of which have been included 

under the genera Neodon and Phaiomys by others. 

Martin (1987) has questioned the reality of P. mcknowni 

and P. hibbardi with reason (also see Repenning, 1983). 

Discussion.-As diagnosed, Pitymys would include 

North American Pedomys but not all species included 

under either Pitymys or Neodon in the Old World. Two 

lineages of Pitymys exist in North America: the pineforum species group and the quasiater species group. The 

pinetorum species group, to which the name Pitymys 

belongs, is native to North America and probably not 

known in the Old World, whereas the quasiater species 

group is derived from the Old World forms that immigrated to the United States with Microtus paroperarius 

about 850,000 years ago (Repenning, 1983). 

By virtue of belonging to the same monophyletic 

group, Pedomys belongs in the pinetorum species group. 

The quasiater group is immigrant to North America probably a few tens of thousand years before the Cheetah 

Room fauna lived, and it is not represented in this fauna; 

it is present in the possibly younger Hansen Bluff faunal 

sequence in the Rocky Mountains and in the younger 

Cudahy fauna of the Great Plains. To it belong the 

species of the Old World assigned to Pitymys and to 

Neodon. 

To rectify this double-lineage Pitymys in North 

America, it would be simplest to put the quasiater species 

group in a different genus. The genus Neodon is logical, 

but such an action would have three consequences: 

1. Considerable work necessary to learn the history 

of Old World Pitymyinines well enough to be certain that 

the pinetorum species group never dispersed there, and, 

hence, that the species group, or the genus Pitymys, is 
not present in the Old World. Several living species in Eurasia appear to conform to the characters of the pinetorum 

species group, including the Pitymys savii group of Miller 

(1912) as well as Neodon carruthersi and N. irene. 

2. The politics involved in convincing Old World 

researchers that there is no Pitymys in their faunas. 

3. The politics involved in convincing North 

American researchers that several of their species of 

Pitymys belong in the genus Neodon. 

The two species groups differ in the complication 

of the anteroconid complex, as well as in origin. The 

pinetorum species group usually has obviously wide confluence between the dentine fields of the opposing first 

pair of additional triangles (triangles 4 and 5) and that 

of the more anterior part of the anteroconid complex. 

The part of the anteroconid complex anterior to the 

paired additional triangles also is less complicated. 

Although it usually has secondary wings, they are weakly formed in most individuals (about 96 percent) because 

of shallow reentrants marking their anterior limits; they 

seldom approach the condition of being secondary additional triangles. This lineage evolved in North America 

from North American Allophaiomys as indicated by van 

der Meulen (1978) and by the Cheetah Room fauna. It 

contains the generic type species, Pitymys pinetorum. 

The quasiater species group usually has complete, 

or nearly complete, closure between the dentine fields of 

the first pair of opposing additional triangles and the 

more anterior part of the anteroconid complex. The 

anterior part of the anteroconid complex is more prominent in the quasiater species group and has a more complicated structure, to the point of frequently developing 

a second pair of opposing additional triangles (triangles 

6 and 7). This lineage appears to have immigrated to the 

United States about 850,000 years ago as Pitymys 

meadensis (Repenning, 1983). 

PITYMYS HIBBARD! Holman, 1959 

(Figure 5) 

Dental diagnosis.-A species of Pitymys in the 

pinetorum species group with no or only very weak 

development of secondary wings on the cap of the 

anteroconid complex, differing from the quasiater species 

group, and a small, plain, crescentic cap, differing from 

other species of the pinetorum species group. The buccal additional triangle (triangle 4) may slope posteriorly 

and have a rounded salient angle as in many individuals 

of P. pinetorum or may be sharply triangular and project from the midline of the tooth at an angle closer to 

normal as in Pitymys ochrogaster. First lower molar 

varies in length from 2.4 mm to 3.0 mm in the Cheetah 

Room fauna, and the type specimen is 3.2 mm in this 

dimension (fig. 5). 

0 

II I I I I 

1 mm 

I 

Figure 5. First lower molars of Pitymys hibbardi. A 

and B, left; C and 0, right. A, Holotype from the 

Williston fauna of Florida, UF/FGS V5929. B, Typical 

form from the Cheetah Room fauna, USNM 264313. 

C, Individual overlapping the morphology of Pitymys 

pinetorum from the Cheetah Room fauna, USNM 

264314. 0, Individual overlapping the morphology 

of Allophaiomys p/iocaenicus from the Cheetah Room 

fauna, USNM 254315. 

Discussion.-Pitymys hibbardi was named from 

the Rancholabrean Williston fauna of Florida (Holman, 

1959) and seems remarkably primitive for so geologically young a species (fig. 5A). Virtually nothing is known 

of its geochronologic range, however, the Cheetah Room 

fauna being its second or third fossil record. Martin 

(1987) suggested that the species is Pitymys pinetorum, 

which it could be on the basis of the type material (a single 

specimen), as individuals of P. pinetorum overlap the 

morphology of P. hibbardi. (See van der Meulen, 1978, 

fig. 13-C.) However, only 3 of the 52 first lower molars 

Systematics 17 
from the Cheetah Room fauna overlap the typical morphology of Pitymys pinetorum. (See van der Meulen, 

1978, fig. 13-A,B,D, and F-K; also see fig. 5C of the 

present report.) It is here considered a valid species. 

Martin (1987) stated that a decision will be made 

regarding the reality of Pitymys hibbardi upon the completion of work in progress. Should this work show the 

population from the type locality of P. hibbardi to be 

indistinguishable from P. pinetorum, a new species will 

have to be erected for the Cheetah Room specimens. 

The morphology of the anteroconid complex of the 

first lower molar of Pitymys hibbardi from the Cheetah 

Room fauna has a range of individual variation that 

overlaps both Allophaiomys pliocaenicus and typical 

Pitymys ochrogaster and Pitymys pinetorum. In the sample are three mls that overlap the form typical of Pitymys 

pinetorum (fig. 5C) and perhaps a dozen mls that could 

not certainly be assigned to either Pitymys or 

Al/ophaiomys. (These last have been counted with 

Allophaiomys, and fig. 5D shows an m1 that was counted 

as Pitymys but is close to Allophaiomys.) Thus the sample from the Cheetah Room fauna supports the interpretation of van der Meulen (1978) that the North 

American lineage of Pitymys derives from the North 

American population of Allophaiomys, an interpretation 

that was based on study of a considerably younger fauna. 

From the variation in the buccal additional triangle of 

Pitymys hibbardi from the Cheetah Room fauna, both 

Pitymys pinetorum and P. ochrogaster could be derived 

from it. 

Subfamily ONDATRINAE, new form 

Dental diagnosis. -Cricetid rodents with hypsodont, triangularly prismatic cusps on their cheek teeth; 

m 1 with posterior loop and five basic alternating 

triangles, differing from all other microtine subfamilies 

except possibly the Dicrostonychinae; triangle 4 may be 

weak in early forms, obscured by a shallow third buccal 

reentrant that leaves an islet in early wear, but triangle 

5 always present; anteroconid complex based upon a 

single, semicircular anteroconid cap with lingual reentrant 

and wing evolving before buccal one, differing from the 

Arvicolini; M3 with two to three alternating triangles; 

teeth rooted except in Neofiber, and first upper molar 

retains primitive lingual third root; large size. 

Included tribes.-Ondatrini and Pliomyini. 

Discussion.-The Ondatrinae trace their ancestry 

back to the little-known genus Ischymomys described by 

Gromov and Polyakov (1977) under the authorship of 

V.S. Zazhigin. This genus is from the Ermak Series (late 

Hemphillian equivalent) along the Ishim River near 

Petropavlovsk, northernmost Kazakhstan, but very little 

is known of it. Although very low crowned, its cheek teeth 

are characterized by five alternating triangles on m1 and 

18 Microtine Rodents, Hamilton Cave, West Virginia 

its M3 had an anterior loop, two alternating triangles, 

and a posterior loop that was basined; some M3s show 

a breaching of the posterior basin. 

By Late Ruscinian time in Europe (Blancan II 

equivalent in North America), early ondatrines appeared 

in Europe (P/iomys and Dolomys) with five alternating 

triangles on the first lower molar. These contrast strongly with the coeval primitive arvicolines that had only 

three. Not until it was realized that the ondatrines began 

their history of hypsodonty with five alternating triangles 

could this seeming inconsistency be properly evaluated. 

Tribe ONDATRINI, Kretzoi, 1955 

Dental diagnosis.-Ondatrine rodents of large size 

with anterobuccal reentrant of M3 unreduced, differing 

from the Tribe Pliomyini; size increases with evolution; 

one genus is rootless. 

Included genera.-Dolomys, Ischymomys, Neofiber, Ondatra, and Pliopotamys. 

Discussion.-These are the muskrats, and they have 

a history that began in Asia more than 5 million years 

ago, in Europe about 4.3 million years ago, and in North 

America 3.7 million years ago. Although never a diverse 

group, the Ondatrini were and are widespread and conspicuous members of many faunas. 

Genus ONDATRA, Link, 1795 

(Muskrats) 

Dental diagnosis.-Ondatrinine rodents of large 

size, differing from other genera; with rooted cheek teeth, 

differing from Neojiber; differing from Pliopotamys in 

presence of well-developed fifth lingual reentrant in the 

anteroconid complex of at least little-worn first lower 

molars; cement usually present to some degree and 

cellular; the dentine tract on the lingual salient angle of 

the posterior loop of the first lower molar progressively 

elongated, but essentially absent on the oldest species, 

Ondatra idahoensis; length of m1 averages more than 

4.5 mm. 

Included species.-Ondatra annectens, 0. idahoensis, 0. nebraskensis, and 0. zibethicus. 

Discussion.-Nelson and Semken (1970) have 

established a progressive increase in size from Pliopotamys to the living species of Ondatra, as well as considerable overlap. Regrettably, it appears that any single 

specimen of Ondatra is virtually. unidentifiable to species 

because of individual variability in length of the first 

lower molar. Furthermore, generic assignment can be 

questionable in the region of transition between 

Pliopotamys and Ondatra; Pliopotamys meadensis is a 

good example of a species that has individuals that fall 

into the two different genera; some have a fifth lingual 
reentrant that is well formed, and many have an m1 that 

is longer than 4.5 mm, and the lingual dentine tract on 

the posterior loop of m1, while low, is higher than in Ondatra idahoensis. 

ONDATRA ANNECTENS (Brown), 1908 

Dental diagnosis.-A species of Ondatra with four 

buccal reentrants on the first lower molar, differing from 

0. idahoensis; differing from other species in that the 

fourth buccal and the fifth lingual reentrants are not as 

deep as the more posterior reentrants and are lost with 

wear, and dentine tract on the buccal salient angle of the 

posterior loop of m1 does not reach the occlusal surface 

until roots are fully formed; length of m1 4.9 to 6.1 mm. 

Discussion.-This species covers a variety of very 

similar forms that span the time between the beginning 

of Irvingtonian I faunas (Olduvai event, about 1.8 m.y. 

ago; Java fauna, South Dakota; El Casco fauna, California) to the end of Irvingtonian II faunas (about 450,000 

years ago; Cumberland Cave fauna, Maryland; Cudahy 

fauna, Kansas). During this period of 1.35 million years 

the first lower molar of this species varies in length with 

no apparent relationship to time (Martin and Tedesco, 

1976). 

Eight first lower molars have been recovered from 

the Cheetah Room locality, of which three are complete 

enough to measure their anteroposterior length. These 

measure 4.9, 4.9, and 5.0 mm; they are smaller than has 

been reported from the Cudahy fauna of Kansas. In addition, it appears that the dentine tract on the lingual 

salient angle of the posterior loop of this tooth would 

interrupt the enamel pattern of the occlusal surface at a 

later stage of wear than on the Cudahy specimens seen. 

One is tempted to suggest that they represent a slightly 

older stage of evolution, but the results of the studies of 

others, such as Martin and Tedesco (1976) and ~elson 

and Semken (1970), caution against this. The first upper 

molar has three distinct roots, and the lingual root is not 

fused to the anterior one as it is in living Ondatra. 

Subfamily LEMMINAE, Gray, 1825 

Dental diagnosis.-Cricetid rodents with rootless 

cheek teeth formed by hypsodont, triangularly prismatic 

cusps; m 1 with a posterior loop, three basic alternating 

triangles, and an anteroconid complex that is a simple 

trefoil consisting of two wings and a roughly rectangular 

cap with no enamel on its anterior face, differing from 

the Prometheomyinae, Ondatrinae and the Dicrostonychinae; M3 with three hypsodont lophs, one formed 

by the anterior loop, another by the anterior alternating 

triangle, and the third by the posterior alternating triangle 

in confluence with the anterior part of the breached 

posterior loop, the posterior part forming a hooked loop 

lacking enamel on its posterior face, differing from all 

other subfamilies; reentrants with cement and lower 

incisor medial to the cheek teeth, differing from at 

least early forms of all other subfamilies except the 

Dicrostonychinae. 

Included tribes.-Lemmini and Synaptomyini. 

Discussion.-The oldest lemmine is a full-fledged 

lemmine with rooted and cemented cheek teeth differing 

little in pattern from the living Lemmus. It is from 

Bashkir A.S.S.R. and is correlative to the western European Late Ruscinian faunas, about 4 million years old. 

The subfamily is marked by little change in the dentition 

and its ancestry is not known. 

Tribe SYNAPTOMYINI, von Koeni.gswald and 

Martin, 1984b 

Dental diagnosis.-Lemmine rodents with anterolingual reentrant of M3 reduced or not elongate; central 

buccal reentrant extends more than halfway across the 

tooth, differing from the Lemmini. 

Included genera.-Mictomys, Plioctomys, and 

Synaptomys, to be discussed. 

Discussion.-The genus Synaptomys was established in 1858 by Baird to include the North American 

bog lemmings, the northern Synaptomys borealis 

(Richardson) and the southern Synaptomys cooperi 

Baird. Howell (1927) revised the genus and established 

as subgenera the names Mictomys, True for the northern 

form, and Synaptomys, Baird for the southern. 

Gromov and Polyakov (1977) included Synaptomys, with Lemmus and Myopus, in the Tribe Lemmini 

and von Koenigswald and Martin ( 1984b) elevated this 

grouping to the Subfamily Lemminae, and restored the 

northern Mictomys to full generic status with three 

subgenera: Metaxyomys, Kentuckomys, and Mictomys. 

Von Koenigswald and Martin also retained two subgenera in the southern Synaptomys: Plioctomys and 

Synaptomys. They placed both genera, Mictomys and 

Synaptomys, in the Tribe Synaptomyini. 

Thus far, the Tribe Synaptomyini would seem to 

include two genera: Synaptomys and Mictomys. Synaptomys would include two subgenera: P/ioctomys and 

Synaptomys; Mictomys would include three subgenera: 

Metaxyomys, Kentuckomys, and Mictomys. For the following reasons, we feel that at least three genera should 

be recognized-Piioctomys, · Mictomys, and 

Synaptomys-and that Mictomys should include only two 

subgenera, Kentuckomys and Mictomys. 

The case for Plioctomys.-Suchov (1976) defined 

Plioctomys as a subgenus of Synaptomys, thereby making Synaptomys the oldest known living microtine genus. 

Von Koenigswald and Martin (1984b) noted that P/ioctomys had a distinctive Schmelzmuster that was shared 

by Synaptomys rinkeri Hibbard from the latest Blancan 

Systematics 19 
faunas of the Great Plains of the United States. 

Schmelzmuster is a distinctive character of value in taxonomy; thus these authors moved Hibbard's species to 

the subgenus Plioctomys, following the taxonomy of 

Suchov. Significantly, in spite of the different 

Schmelzmuster of subgenus Plioctomys, when compared 

to that of the subgenus Synaptomys, these authors did 

not question the assignment of subgenus Plioctomys to 

the genus Synaptomys. 

In 1956 C.W. Hibbard introduced the name Synaptomys (Synaptomys) rinkeri [ = Plioctomys rinkeri 

(Hibbard) in our terminology, modifying von Koenigswald and Martin] for a fossil lemming that he described 

from the late Pliocene Dixon fauna of Meade County, 

Kansas. In so doing he stated (1956, p. 169), "I find no 

characters in Synaptomys (S.) rinkeri that would keep it 

from being the ancestral stock of the Recent S. cooperi 

or from being ancestral to other later Pleistocene forms 

of the subgenus Synaptomys, exclusive of the S. vetus 

group." The "S. vetus group" was then considered by 

some to be closely related to the living subgenus Mictomys 

(Wilson, 1934), although Hibbard (1956, p. 169) believed 

that it represented a ''side branch that split off from the 

Synaptomys stock during the Pliocene,'' implying a 

position intermediate between the lineages of the subgenera Mictomys and Synaptomys as he was using these 

names. 

Hibbard's assumption of a rectilinear relationship 

between the 2.6- to 2.0-million-year-old Plioctomys 

rinkeri and living Synaptomys cooperi is most recently 

repeated in the retention of Plioctomys as a subgenus of 

Synaptomys by von Koenigswald and Martin (1984b) and 

is most recently illustrated by Repenning and others 

(1987) (this report, fig. 6). 

With the exception of placing "Synaptomys (S.) 

rinkeri" in the subgenus Plioctomys, the evolutionary 

concepts expressed in 1956 by Hibbard have remained unchanged; and this is strange as the species and its subgenus 

Plioctomys [as used by von Koenigswald and Martin 

(1984b)] seem to have become extinct 2 million years ago, 

whereas Synaptomys (Synaptomys) cooperi does not appear in the fossil record until perhaps 1.2 million years 

later, sometime before 740,000 years ago in the Fyllan 

Cave fauna of Texas (Alisa Winkler, written commun., 

1987). 

These intervening 1.2 million years are marked by 

an absence of both Plioctomys and Synaptomys; this is 

a gap in the fossil record as long as the combined temporal spans of both Plioctomys rinkeri and Synaptomys 

cooperi. Moreover, this gap is marked by an abundance 

of Mictomys in a dozen or so faunas across the Great 

Plains, in the area where Plioctomys is last seen and where 

Synaptomys is first seen, as well as in those faunas containing Mictomys west of the Rocky Mountains where 

Plioctomys and Synaptomys would not be expected. 

20 Microtine Rodents, Hamilton Cave, West Virginia 

Although a 1.2-million-year gap in the fossil record 

between Plioctomys and Synaptomys, a gap during which 

Mictomys is well known, might be enough to arouse some 

doubt in the relationship, none has been suggested in 

publication. 

The lemmings from the Cheetah Room fauna of 

Hamilton Cave, West Virginia, indicate that the relationship between Plioctomys and Synaptomys is far less direct 

than supposed. They show that the similarity between the 

two is not real but is secondarily derived; Synaptomys 

did not evolve directly from Plioctomys in the conventional sense supposed by Hibbard. The similarity between 

Synaptomys and Plioctomys consists of the symmetrical 

arrangement of the alternating triangles along the tooth 

axis of the lower teeth, rather than a buccal position 

characteristic of Mictomys, and a deep anterior buccal 

reentrant on the m1 of Synaptomys presumably retained 

from Plioctomys. But the deep anterior buccal reentrant 

is not the same on the two, as the alternating triangles 

insert at the middle of the posterior face of the anteroconid complex in Plioctomys and at the buccal corner of 

this face in Synaptomys, and the deep posterior buccal 

reentrant clearly derives from a deepening of this reentrant as it is found in Mictomys (fig. 6). 

As will be discussed, the sample from the Cheetah 

Room fauna indicates that a reversal of both characters 

resulted in the development of Synaptomys out of Mictomys. For this reason we see no direct relationship between Plioctomys rinkeri and Synaptomys cooperi and 

elevate Plioctomys to full generic status, ancestral to, but 

not included in, the genus Synaptomys. 

Thus the Tribe Synaptomyini includes three genera: 

Plioctomys, Mictomys, and Synaptomys. Mictomys alone 

contains subgenera: Mictomys, Kentuckomys, and 

Metaxyomys. Kentuckomys seems to be a valid subgenus 

based upon its relatively long lower incisor and distinctive Schmelzmuster (von Koenigswald and Martin, 

1984b). 

The case against Metaxyomys.-The lack of reduction of the anterior buccal reentrant of the first lower 

molar in Synaptomys vetus from the Grand View fauna 

of Idaho (fig. 6), and other faunas, has led to the introduction of a separate subgeneric name, Synaptomys 

(Metaxyomys) vetus, with the concept, first expressed by 

Hibbard (1956), of an evolutionary intermediate position 

between the lineages of the living Mictomys and Synaptomys, not questioning the direct derivation of Synaptomys from Plioctomys (Zakrzewski, 1972; von 

Koenigswald and Martin, 1984b). The posterior buccal 

reentrant of m1 is reduced in Synaptomys vetus, as it is 

in Mictomys, but the anterior one is not, presumably as 

in Synaptomys. 

As indicated by von Koenigswald and Martin 

(1984b), two diagnostic characters mark the lower first 

molar of Mictomys: (.1) confluence of triangles 1 and 
en 

>-

~ 

0 

._ 

u 

0 

:::::i 

a.. 

LEMMINAE 

MICTOMYS 

REBIELICE 

(3.0 Mal 

DIXON 

(2.4Mal 

EL CASCO 

11.6 Mal 

I 

IY 

SYNAPTOMYS 

NEW PARIS 

(0.1 Ma and living) 

Figure 6. Right lower first molars of the Tribe Synaptomyini 

and left lower first molars of the Tribe Lemmini. Reproduced 

with slight modification from Repenning and others, 1987. This 

diagram shows the conventional concept of evolution of the 

Synaptomyini prior to discovery of the Cheetah Room fauna 

of Hamilton Cave; Synaptomys cooperi (from New Paris fauna, 

Pennsylvania) is considered as being derived from Plioctomys 

rinkeri (specimen from Dixon fauna, Kansas). Dashed arrow 

shows derivation indicated by the Cheetah Room fauna. 

2 with consequent shallowing of the posterior buccal 

reentrant, and (2) buccal shifting of the tooth axis with 

consequent shallowing of both buccal reentrants. As 

shown in figure 6, confluence develops first and is 

evident in Synaptomys vetus. Buccal shifting of the tooth 

axis had not yet begun in this species and became evident only in Mictomys kansasensis, of which an early 

form from the El Casco fauna of California is shown in 

figure 6. 

Lack of buccal shifting of the tooth axis in both 

Synaptomys vetus and the species of P/ioctomys is also 

shown by the central position of the commissure between 

the alternating triangles and the posterior face of the 

anteroconid complex; as pointed out above, this differs 

CUDAHY 

(0.6Mal 

LEMMUS 

OSZTRAMOS 3 

(3.0Mal 

~ 

(living) 

DZERAVA SKALA 

(0.1 Ma and living) 

Other specimens shown are Plioctomys mimomiformis from 

Rebielice-Krolewskie fauna, Poland; Mictomys vetus from 

Grand View fauna, Idaho; an early form of Mictomys kansasensis 

from El Casco fauna, California; Mictomys me/toni from Cudahy 

fauna, Kansas; Mictomys n. sp. from Snowville fauna, Utah; 

and Mictomys borealis from Alaska. The two left lower molars 

of Lemmus are from Osztramos-3 fauna, Hungary, and 

Dzerava-Skala fauna, Czechoslovakia. 

from the condition in Synaptomys. Thus the structure of 

the first lower molar of Synaptomys vetus does not indicate a lineage separate from those represented by living Mictomys and Synaptomys, but indicates that the 

species is transitional from Plioctomys to Mictomys and 

has developed one of the two apomorphic characters that 

define Mictomys. The other character, shifting of the 

tooth axis, has not yet developed; and in this character 

S. vetus retains the plesiomorphic condition of Plioctomys. The species Synaptomys vetus is, instead, the first 

of the Mictomys lineage and the subgenus Metaxyomys 

is here suppressed, as it is based upon a demonstrably 

false concept of the phylogenetic pattern in the monophyletic lineage of Mictomys. 

Systematics 21 
Genus MICTOMYS, True, 1894 

(Northem bog lemmings) 

Dental diagnosis.-A synaptomyinine rodent with 

alternating triangles 1 and 2 completely confluent on the 

lower molars, differing from Synaptomys and 

Plioctomys. 

Included species.-Mictomys anzaensis, M. 

borealis, M. kansasensis, M. /andesi, M. me/toni, and M. 

vetus, as well as at least one unnamed species. 

Discussion.-The genera Synaptomys and Mictomys now live only in North America, although the 

ancestral form, Plioctomys mimomiformis, is first known 

from deposits in Bashkir A.S.S.R. that are about 4 

million years old and is last known in Siberian (Sher and 

others, 1979) and Alaskan (Repenning and others, 1987) 

Beringia from deposits about 2.4 million years old. 

As established through the similarity of their 

Schmelzmuster by von Koenigswald and Martin (1984b), 

Plioctomys also spread southward to the conterminous 

United States by 2.6 million years ago. This immigration 

into the United States was as the derived species P. rinkeri 

(Hibbard), which dispersed down the eastern side of the 

Rocky Mountains, and as the derived genus, Mictomys 

vetus (Wilson), which dispersed down the Pacific Coast. 

Mictomys vetus and Plioctomys rinkeri appeared 

in the United States at the same time; Mictomys is first 

known about 3 meters below the Gauss/Matuyama 

polarity boundary in Idaho and Arizona; Plioctomys 

rinkeri is first known about 3 meters below the same 

polarity boundary in northern Texas (G.E. Schultz, oral 

commun., 1985). 

Genus SYNAPI'OMYS, Baird, 1858 

(Southem bog lemmings) 

Dental diagnosis.-A synaptomyinine rodent with 

alternating triangles 1 and 2 not confluent on the lower 

molars, differing from Mictomys; alternating triangles 

of the first lower molar connected to the buccal corner 

of the anteroconid complex, differing from Plioctomys. 

Included species.-Synaptomys cooperi, including 

the large race that has been called Synaptomys australis. 

Discussion.-The bog lemmings of the Cheetah 

Room fauna in Hamilton Cave present a problem and 

at the same time suggest an ancestry for Synaptomys 

cooperi other than the direct derivation from Plioctomys 

rinkeri as envisioned by C. W. Hibbard in 1956. This 

problem centers on the transitional morphology of the 

lower molars from the Cheetah Room· fauna. 

The distinction between the teeth of the two living 

bog lemming genera Mictomys and Synaptomys lies 

almost entirely in characters of the lower cheek teeth (fig. 

7). In Mictomys the posterior buccal reentrants of all 

22 Microtine Rodents, Hamilton Cave, West Virginia 

0 

!Ill!! 

Figure 7. Left lower first molars of living bog lemmings, occlusal views. A, Mictomys borealis dalli, Seward Peninsula, 

Alaska. R.L. Rausch No. 26132. 8, Synaptomys cooperi, 

Springfield, Illinois. ISM No.688275. Note depth of the two 

primary buccal (left side) reentrants and the effect on the configuration of the alternating triangles. 

lower cheek teeth are weakly developed, resulting from 

complete confluence between the posterior two alternating triangles (triangles 1 and 2). In the more modern 

of the species of Mictomys, the anterior buccal reentrant 

is similarly reduced and a buccal location of the commissure between the anteroconid complex and the 

anterior alternating triangle (triangle 3) results. 

In Synaptomys the buccal reentrants are more like 

those of other microtine rodents, and the central alternating triangle (triangle 2) is completely separated (or 

nearly so) from the posterior one (triangle 1) by a narrowing, or even closure, of the dentinal areas of the triangles 

within the enamel margins. In addition, the connection 

between the anteroconid complex and the most anterior 

alternating triangle (triangle 3) tends to be more centrally located, although not in the same way that it is centrally located in Plioctomys or even in the earliest species 

of Mictomys, Mictomys vetus from the late Pliocene. 

In Synaptomys the commissure between the 

anteroconid complex and the anterior alternating triangle 

originates on the third triangle at the center of the tooth, 

but it inserts on the buccal side of the anteroconid complex. In Plioctomys (fig. 6, Rebielice) and Mictomys vetus 

(fig. 6, Grand View; fig. SA), the insertion of the commissure is in the center of the posterior side of the 

anteroconid complex because the anterior buccal reentrant is not reduced and the anterior lingual reentrant not 

correspondingly elongated, which would require that the 

insertion of the commissure be on the buccal side of the 

anteroconid complex. 

As discussed, the lack of reduction of the anterior 

buccal reentrant in Mictomys vetus, which led to the 
0 1mm II I I II I 

Figure 8. Left lower first molars of Mictomys. A, Mictomys 

vetus from the Grand View fauna, Idaho; age about 2.4 million 

years, USGS specimen. Posterior (lower) buccal reentrant is 

reduced, but anterior one is still as deep as in ancestral genus 

Plioctomys. B, Unnamed species of Mictomys from the 

Snowville fauna, Utah; age about 500,000 years, UCMP 

124887. Similar to living species except that base of the incisor 

is farther back, buccal reentrants are somewhat deeper, lingual 

triangles are thicker in anteroposterior dimension, and enamel 

wall on posterior side of triangles is thin. This species greatly 

resembles Mictomys (Kentuckomys) kansasensis. C, Fragment 

of tooth from the Cheetah Room fauna that has the features 

of Mictomys, USNM 184100, a right first lower molar with drawing reversed. 

introduction of the separate sub generic name, Mictomys 

(Metaxyomys) vetus, is not intermediate, but is a primitive 

state in the rectilinear evolution of Mictomys (fig. 6). The 

similarity of the anteroconid commissure of Synaptomys 

cooperi to that of Mictomys vetus is not real, but secondarily derived. 

Figure SA shows a left lower molar of Mictomys 

vetus from the Grand View fauna of Idaho with unreduced and incompletely reduced buccal reentrants. 

Figure SB shows the corresponding tooth of an unnamed 

species of Mictomys from Snowville, Utah, believed to 

be about 500,000 years old. This unnamed species has 

much greater reduction of the buccal reentrants, but the 

lingual triangles are broader anteroposteriorly and the 

enamel is noticeably thicker on the anterior faces of the 

triangles than in the living species; the species greatly 

resembles Mictomys (Kentuckomys) kansasensis, but its 

Schmelzmuster is not known; the position of the base of 

the lower incisor varies from being opposite the middle 

of m3 to being opposite the anterior face of this molar. 

The same species, called ''Synaptomys (Mictomys) sp.'' 

by Gidley and Gazin (1938), is known from Cumberland 

Cave, Maryland, and van der Meulen (1978, p. 132) has 

noted how it differs from named species. 

Seventy-two bog lemming teeth have been 

recovered in the Cheetah Room locality of Hamilton 

Cave, of which 22 are first lower molars; figure 8C shows 

the only first lower molar (incomplete) that conforms to 

the characters of Mictomys. This single tooth most 

resembles the living species M. borealis, rather than contemporary M. kansasensis or M. me/toni; but the sample size is too small to suggest significance. The rest of 

the bog lemming lower molars from the Cheetah Room 

fauna are intermediate between Mictomys and Synaptomys (5 of 21 first lower molars or 24 percent) or conform to the characters of Synaptomys cooperi (16 of 21 

first lower molars or 76 percent). A sample of the first 

lower molars is shown in figure 9. 

As shown in figure 8C and figure 9, the recovered 

sample of bog lemming teeth from the Cheetah Room 

fauna indicates that the population was morphologically 

Figure 9. Left lower first molars of bog lemmings 

from the Cheetah Room fauna of Hamilton Cave, 

West Virginia. Specimens show a gradation of features 

from almost those of Mictomys on upper left to those 

of Synaptomys on lower right. A, USNM 184091; 8, 

USNM 23888; C, USNM 264306; D, USNM 264307. 

Systematics 23 
intermediate between Mictomys and Synaptomys. The 

development of the genus Mictomys is recorded by about 

1, 760,000 years of fossil history before the existence of 

the Cheetah Room fauna and before any record of Synaptomys cooperi. That part of the population represented 

by this fauna that conforms to the characters of Synaptomys would seem to be the oldest record of any bog 

lemming that could be called Synaptomys cooperi. 

Although some of this variable population 

resembles the ancestral genus Plioctomys in the development of the alternating triangles, none of it has the 

anteroconid complex attached to the alternating triangles 

in the central manner found in Plioctomys. Instead, the 

variation in the Cheetah Room faunal sample shows that 

the pattern of the tooth enamel on the first lower molar 

of Synaptomys cooperi may derive from a secondary 

deepening of the buccal reentrants of Mictomys. Thus, 

as has been discussed, Plioctomys is here given full generic 

status and suppressed as a subgenus of Synaptomys, 

which appears to be a derivative of Mictomys. 

Von Koenigswald and Martin ( 1984b) presented a 

cladogram showing the relationships of the Subfamily 

Lemminae in which five characters were used to diagnose 

the included taxa. These were: 

1. Structure of the last upper molar, used to 

separate the Tribes Synaptomyini and Lemmini; in the 

present report this character is given in the tribal 

diagnoses. 

2. Asymmetry of the reentrants and triangles on 

the lower teeth, used to separate Plioctomys, Synaptomys, and Mictomys; they are discussed at length herein 

with an analysis of their cause and parallel development. 

This character is discussed in the diagnoses. The 

significance of this character in the bog lemmings of the 

Cheetah Room fauna appears to be little, as the sample 

of the population is clearly shifting from one extreme to 

the other (figs. 8C and 9). 

3. Confluence of the first and second alternating 

triangles on the lower teeth, used to separate Mictomys 

from Synaptomys and Plioctomys. This has been discussed at length herein, is the basis of diagnosis of the 

two genera, and varies individually in the sample from 

the Cheetah Room fauna (fig. 9). 

4. Position of the base of the lower incisor, described in terms relative to the last two lower molars. This 

is an awkward character in that relatively complete 

specimens are needed for evaluation and individual variation is great. Von Koenigswald and Martin (1984b) listed 

three conditions for the base of the lower incisor: (a) 

behind the last molar, (b) between the second and third 

molar, and (c) at the second molar. Shorter incisors were 

considered more derived. 

Six modern specimens of Synaptomys cooperi from 

Pennsylvania, Illinois, Missouri, and Kansas were examined for this character; and the posterior limit of the 

24 Microtine Rodents, Hamilton Cave, West Virginia 

incisor capsule varied from 0.8 mm behind the posterior 

face of the last molar to opposite the middle lingual 

salient angle of this tooth. One fossil specimen of this 

species from New Paris, Pennsylvania, had the base of 

the incisor at the anterior face of the m3, whereas the 

specimen described by Gidley and Gazin (1938) from 

Cumberland Cave, Maryland, had it at the posterior face 

of m3. One mandibular ramus from the Cheetah Room 

fauna (a Synaptomys cooperi morphotype) was complete 

enough to interpret; it had the base of the incisor at least 

as far back as the middle of the last molar. Thus the position of the base of the incisor in Synaptomys cooperi 

appears to be primitive and to vary between conditions 

(a) and (b). 

Two specimens of Mictomys borealis from Alaska 

had the base of the incisor at the posterior salient angle 

of the second molar, condition (c) (advanced). The unnamed species of Mictomys believed to be about 500,000 

years old (fig. 8B from the Snowville fauna, Utah) had 

the base of the incisor at the middle of the last molar, 

condition (a); however, this species from Cumberland 

Cave, Maryland (Gidley and Gazin, 1938) had the base 

of the incisor at the anterior face of the last molar, condition (b). Although living Mictomys borealis may be advanced in this character, fairly modern fossil species of 

the genus appear to be more primitive. 

On the other hand, the oldest species of the genus, 

Mictomys vetus from the approximately 2.4-million-yearold Grand View fauna of Idaho (fig. SA)~ has the base 

of the incisor in front of the anterior face of the last 

molar, condition (b) (moderately advanced, more so than 

many of its descendants). 

Although of a limited sample, these observations 

are in agreement with those indicated by von Koenigswald 

and Martin (1984b), except that they did not indicate the 

individual variability in the position of the base of the 

incisor. The observations of the position of the base of 

the lower incisor may be summed up as follows: the most 

primitive condition is found in Synaptomys cooperi (living and fossil), in the late Pleistocene unnamed species 

of Mictomys, and in the subgenus Mictomys (Kentuckomys); the most advanced condition is found in the 

living Mictomys borealis; and the oldest species assigned 

to Mictomys, Mictomys vetus, has a condition intermediate between most advanced and most primitive 

(the condition in Plioctomys is unknown, although attainable). We find this character quite variable and difficult to interpret. 

5. Schmelzmuster. We have not examined the 

enamel structure and rely upon the statements of von 

Koenigswald and Martin (1984b ). These show that Mictomys borealis, Mictomys me/toni, and Synaptomys 

cooperi have the same Schmelzmuster, whereas Mictomys 

vetus and the two species of Plioctomys share a more 

primitive enamel type. This suggests to us that the 
Schmelzmuster favors an interpretation that Synaptomys 

cooperi is more closely related to Mictomys me/toni and 

M. borealis than to Plioctomys rinkeri. 

The conclusions of von Koenigswald and Martin 

( 1984b) are not challenged here and are matters of agreement in almost all cases. We depart from their opinions 

only in regard to the inclusion of Plioctomys, as a 

subgenus, in the genus Synaptomys; and this seems to 

be supported by the characters that they use, as well 

as by the Cheetah Room fauna. Synaptomys differs from 

Plioctomys in its Schmelzmuster, the position of the 

base of its incisor, the origin of the lack of confluence of triangles 1 and 2 on the lower teeth, and the 

origin of the symmetry of the triangles and reentrants 

on the lower teeth. They share a similar last upper 

molar, which separates both of them from the Tribe 

Lemmini. 

We are unable to assign the bog lemming population from the Cheetah Room fauna to a genus or a 

species, although 76 percent of the sample seen does not 

differ from Synaptomys cooperi. 

W OTHER 

::\E DERIVED 

~GENERA 

~o 

-1 

-2 

~a 

en 

::;) 

a. 

0 

> 

:::E 

"0 

c 

cu 

en 

::;) 

:::E 

:::E 

PLIOCTOMYS 

!

Kansas4 Alaska, Yakutia, Mongolia- P. rink.eri 

P. mimomiformis Texas~ 

P. rinkeri --------------------~ ------~ 

Poland -P. mimomiformis ~ ~ 

BOG LEMMING HISTORY 

The history of the bog lemmings (fig. 10) begins 

in eastern Europe about 4 million years ago. The earliest 

known form is fully hypsodont with no roots on the cheek 

teeth, and its teeth are fully cemented, apomorphic 

characters totally unknown in any other microtine rodents 

of that early age except for the North American genus 

Pliolemmus, Subfamily Prometheomyinae, whose teeth 

are rootless but have no cement. The ancestor of the bog 

lemmings is unknown. 

It appears that the brown lemmings (Lemmus and 

Myopus) were derived from the same unknown ancestor, or possibly from the earliest bog lemming, and 

therefore the taxonomic structure of von Koenigswald 

and Martin ( 1984b) is here used with the recognition that 

it differs only in rank from that of Gromov and Polyakov 

(1977). 

The earliest known genus of bog lemming, Plioctomys, is of a very generalized nature, and it is as appropriate an ancestor of Lemmus as it is of Mictomys 

MICTOMYS 

4 Living - M. borealis 

~Maryland - M. n. sp. 

Kansas - M. meltoni 

Colorado - M. kansasensis 

Nebraska - M. kansasensis 

California - M. kansasensis 

Kansas - M. landesi 

~ Idaho - M. vetus 

5 

SYNAPTOMYS 

Living - S. cooperi 

Maryland - S. cooperi 

Texas - S. cooperi 

Cheetah Room Fauna, 

West Virginia 

(D- Short buccal reentrant of Ml 

w 

..J,, 

' 

{!j'',iBashkir- P. mimomiformis ~4 

I 

-5 

® -Anteroconid cap enlarged, squarish 

@- Lower triangles 1 and 2 confluent 

@ - Lower buccal reentrants shallow 

@) - @ and @ reversed 

Figure 10. Inferred phylogeny of the Synaptomyini. 

Bog Lemming History 25 
(Kowalski, 1977). Nevertheless, Plioctomys is not greatly different from living genera of the Lemminae. This 

minimal tendency for change is characteristic of the subfamily and is even more evident in the Tribe Lemmini, 

including living Lemmus and Myopus, which are indistinguishable by dental characters from their earliest 

known fossil relatives, all of which have been placed in 

the more specialized genus Lemmus (fig. 6). 

Plioctomys, first known from southern Russia, is 

also known from Poland, Hungary, Mongolia, Yakutiya, 

Alaska, and the Great Plains of the United States. From 

its earliest record until about 2.4 million years ago, the 

latest records in Yakutiya and Alaska, no change is 

recognized in the morphology of its teeth (Repenning and 

others, 1987). However, probably after 3 million years 

ago, part of the population of Plioctomys dispersed 

southward in North America, following two routes, one 

on either side of the Rocky Mountains. They arrived in 

the conterminous United States at the same time on both 

sides of the cordillera; their first fossil records are about 

2.6 million years old and about 5 meters below the 

Matuyama/Gauss polarity boundary in Idaho, Arizona, 

and Texas. 

The southward-dispersing Plioctomys populations 

evolved en route, and the immigrants moving down the 

east side of the Rocky Mountains to the Great Plains did 

so as a new species, Plioctomys rinkeri (the Texas record), 

while those entering the United States west of the Rocky 

Mountains did so as a new genus and species, Mictomys 

vetus (the Idaho and Arizona records). 

Mictomys was successful, and its history up to and 

including the living fauna is well recorded. By 2.0 million 

years ago it had dispersed east of the Rocky Mountains. 

At this time Plioctomys rinkeri seems to have become 

extinct, as there are no younger records; the youngest 

record of the ancestral species is 2.4 million years old in 

Y akutiya and Alaska and P. rinkeri was the last representative of the genus Plioctomys (fig. 10). 

As indicated by the bog lemmings from the Cheetah 

Room fauna of Hamilton Cave, West Virginia, between 

850,000 and 740,000 years ago, possibly before 820,000 

years ago, a population of Mictomys in southeastern 

United States evolved into the living genus Synaptomys. 

To judge from the variation in the Cheetah Room fauna, 

this major transition in tooth morphology took place 

spontaneously, with no obvious environmental or other 

external pressure, and in a very short time. In view of 

the age of the fauna, it seems possible that the change 

simply reflects genetic drift in isolation from populations 

of Mictomys to the west of the first Nebraskan ice sheet 

of the North American ice ages, Hamilton Cave lying 

perhaps 160 km east of the eastern edge of the continental 

ice sheet. It seems to be an obvious case of reversal of 

at least one evolutionary trend in changing morphology. 

Far from being the most ancient of living microtine 

26 Microtine Rodents, Hamilton Cave, West Virginia 

genera, as it appeared to be when Suchov (1976) described 

Synaptomys (Piioctomys) mimomiformis from the 

Simbugino fauna of Bashkir A.S.S.R., Synaptomys now 

appears to be nearly the most recent of living microtine 

genera; only Old World Arvicola is known to have appeared more recently, although North American subgenus 

Phenacomys (Arborimus) may also be younger. 

SUMMARY AND CONCLUSIONS 

The microtine rodents of the Cheetah Room fauna 

of Hamilton Cave, Pendleton County, West Virginia, 

provide surprising information about a number of 

microtine lineages. 

1. The deposits of the Cheetah Room are remarkably old, probably the oldest cave deposits known in the 

eastern United States. They appear to date between about 

850,000 years ago, when Microtus paroperarius first 

entered the United States with the first advance of the 

Nebraskan glaciation [correlated with the first peak of 

Oxygen Stage 22, Richmond and Fullerton (1986)], and 

the 740,000-year-old beginning of the Brunhes Chron. 

The absence of representatives of the immigrant Pitymys 

quasiater species group and the primitive condition of 

Microtus paroperarius suggest that the fauna may be 

older than the 820,000-year-old faunas from Hansen 

Bluff, Colorado. 

2. The Cheetah Room fauna may contain the only 

North American record of the subgenus Mimomys 

(Cromeromys), a subgenus widespread in Eurasia, where 

it ranges in age from possibly 3.5 million to possibly 

850,000 years. The probable temporal correlation of the 

fauna with the first of the Nebraskan ice sheets suggests 

that older North American records may have been in 

Canada. 

3. The morphology of the new subgenus and 

species of Phenacomys, P. (Paraphenacomys) brachyodus, indicates that this genus is represented by at least 

three lineages in the living fauna that are given subgeneric 

designation herein. 

4. The primitive microtinine species Lasiopodomys 

deceitensis is well represented in the Cheetah Room 

fauna. This constitutes the first non-arctic record of this 

species and thus hints at a relationship with the first ice 

sheets. Assignment of this species to the genus is tentative, 

as the fossil record is not complete enough to link these 

early forms with the name-bearing living species. 

5. Although rare in the Cheetah Room fauna, the 

presence of the primitive species Microtus paroperarius 

seems indicated by the presence of "complex" last upper 

molars. The first lower molars in the fauna presumed to 

belong to this species are difficult to separate from Lasiopodomys deceitensis and more closely match specimens 

of Microtus paroperarius from the 820,000-year-old 
parts of the Hansen Bluff faunal sequence of Colorado 

than they do the 610,000-year-old type sample from the 

Cudahy fauna of Kansas, suggesting a comparable age. 

6. An excellent sample of a vole assigned to 

Pitymys hibbardi shows a complete transition between 

ancestral Allophaiomys pliocaenicus and descendants 

Pitymys pinetorum and Pitymys ochrogaster, supporting 

the interpretations of van der Meulen, published 10 years 

ago. Allophaiomys pliocaenicus itself is well represented 

in the fauna, suggesting that its range extended from the 

Rocky Mountains to the East Coast before the ice ages. 

7. One of the more remarkable morphologic transitions known in vertebrate paleontology is recorded in 

the bog lemmings of the Cheetah Room fauna. In this 

transition the living genus Synaptomys is seen to spontaneously derive from a population of the living genus 

Mictomys in the southeastern United States, a derivation 

not previously considered possible. Almost every conceivable variation of individual morphology is represented 

in the sample. Demonstrable origin of Synaptomys from 

a source other than the primitive lemming Plioctomys 

rinkeri requires that Plioctomys be recognized as a full 

genus rather than as a subgenus of the genus Synaptomys. 

REFERENCES CITED 

Baird, S.F., 1858, Mammals-Explorations and surveys for a 

railroad route .... : Washington, D.C., xlvii+757 p. 

Chaline, J., 1974, Esquisse de I' evolution morphologique, 

biometrique et chromosomique du genre Microtus (Arvicolidae, Rodentia) dans le Pleistocene de !'hemisphere 

nord: Societe Geologique de France, Bulletin 16, 

p. 440-450. 

Corbet, G.B., 1978, The mammals of the Palaearctic Region-A 

taxonomic review: British Museum (Natural History), 

314 p. 

Erbaeva, M.A., 1976, The origin, evolution, and intraspecific 

variability of Brandt's vole from the Anthropogene of 

western Transbaikalia, in Gromov, I.M., ed., Rodent 

evolution and history of their Recent fauna: Academy of 

Sciences U.S.S.R., Zoological Institute, Proceedings, v. 66, 

p. 102-116. [In Russian.] 

Gidley, J.W., and Gazin, C.L., 1938, The Pleistocene vertebrate 

fauna from Cumberland Cave, Maryland: United States 

National Museum Bulletin 171, 99 p. 

Grayson, D.K., 1983, The paleontology of Gatecliff shelter, 

Chapter 6 in Thomas, D.H., ed., The archaeology of 

Monitor Valley, 2, Gatecliff shelter: American Museum 

of Natural History Anthropological Papers, Part 1, 

p. 99-126. 

Gromov, I.M., and Polyakov, I.Yu., 1977, Polevki [voles] 

(Microtinae), Mammals, Part III, in Fauna of the 

U.S.S.R.: Academy of Sciences U.S.S.R., Zoological Institute, New Series No. 116, No. 8, 504 p. [In Russian.] 

Guthrie, R.D., and Matthews, J.V., Jr., 1971, The Cape Deceit 

fauna-Early Pleistocene mammalian assemblage from the 

Alaskan arctic: Quaternary Research, v. 1, p. 474-510. 

Hall, E.R., 1981, The mammals of North America: New York, 

John Wiley, 1181 +90 p. 

Hibbard, C.W., 1944, Stratigraphy and vertebrate paleontology 

of Pleistocene deposits of southwestern Kansas: Geological 

Society of America Bulletin, v. 55, p. 707-754. 

__ 1950, Mammals of the Rexroad formation from Fox 

Canyon, Kansas: University of Michigan, Museum of 

Paleontology Contributions VIII, p. 113-192. 

__ 1956, Vertebrate fossils from the Meade Formation of 

southwestern Kansas: Michigan Academy of Sciences, Arts, 

and Letters Papers XLI, p. 145-203. 

Hinton, M.A. C., 1926, Monograph of the voles and lemmings 

(Microtinae), living and extinct: British Museum (Natural 

History), 488 p. 

__ 1932, Note on "Cosomys" Wilson from the Pliocene of 

California: Journal of Mammalogy, v. 13, p. 280-281. 

Holman, J.A., 1959, Birds and mammals from the Pleistocene 

of Williston, Florida: Florida State Museum, Biological 

Sciences Bulletin 5, 24 p. 

Howell, A.B., 1927, Revision of the American lemming mice 

(Genus SYNAPTOMYS): U.S. Dept. of Agriculture, Bureau of Biological Survey, North American Fauna 50, 38 p. 

Janossy, Denes, and van der Meulen, A.J., 1975, OnMimomys 

(Rodentia) from Osztramos-3 north Hungary: Nederlandse 

Akademie van Wetenschappen (Koninklijke)-Amsterdam, 

Proceedings, Series B, v. 78, p. 381-391. 

Johnson, M.L., 1973, Characters of the heather vole, 

Phenacomys, and the red tree vole, Arborimus: Journal 

of Mammalogy, v. 54, p. 239-244. 

Johnson, M.L., and George, S.B., in press, Speciation within 

the Arborimus longicaudus-complex, with a description of 

a new species: Natural History Museum, Los Angeles 

County; Contributions to Science. 

von Koenigswald, Wighart, 1980, Schmelzstructur und Morphologie in den Molaren der Arvicolidae (Rodentia): 

Abhandlung der senckenbergischen naturforschenden 

Gesellschaft 539, p. 1-129. 

von Koenigswald, Wighart, and Martin, L.D., 1984a, The status 

of the genus Mimomys (Arvicolidae, Rodentia, Mamm.) 

in North America: Neues Jahrbuch fur Geologie und 

Palaeontologie, Abhandlungen 168, p. 108-124. 

__ 1984b, Revision of the fossil and Recent Lemminae 

(Rodentia: Mammalia): Carnegie Museum of Natural 

History Special Publication 9, p. 122-137. 

Kowalski, Kazimierz, 1977, Fossil lemmings (Mammalia, 

Rodentia) from the Pliocene and early Pleistocene of 

Poland: Acta Zoologica Cracoviensia, v. 22, p. 297-317. 

Kretzoi, Miklos, 1969, Skizze einer Arvicoliden-PhylogenieStand 1969: Vertebrata Hungarica, v. XI, p. 155-188. 

Martin, R.A., 1975, Allophaiomys Kormos from the Pleistocene 

of North America, in Smith, G.R., and Friedland, N.E., 

eds., Studies on Cenozoic paleontology and stratigraphy 

in honor of Claude W. Hibbard: University of Michigan 

Museum of Paleontology, p. 97-110. 

__ 1987, Notes on the classification and evolution of some 

North American fossil Microtus (Mammalia; Rodentia): 

Journal of Vertebrate Paleontology, v. 7, p. 270-283. 

Martin, R.A., and Tedesco, Richard, 1976, Ondatra annectens 

(Mammalia:Rodentia) from the Pleistocene Java Local 

Fauna of South Dakota: Journal of Paleontology, v. 50, 

p. 846-850. 

References Cited 27 
Maser, Chris, Mate, B.R., Franklin, J.F., and Dyrness, C.T., 

1981, Natural history of Oregon coastal mammals: Pacific 

Northwest Forest and Range Experiment Station, U.S. 

Forest Service, General Technical Report PNW-133, 

496 p. 

Mead, J.I., Thompson, R.S., and VanDevender, T.R., 1982, 

Late Wisconsinian and Holocene fauna from Smith Creek 

Canyon, Snake Range, Nevada: San Diego Society of 

Natural History Transactions, v. 20, p. 1-26. 

van der Meulen, A.J., 1973, Middle Pleistocene smaller mammals from the Monte Peglia (Orvieto, Italy), with special 

reference to the phylogeny of Microtus (Arvicolidae, 

Rodentia): "Quaternaria" XVII, 144 p. 

__ 1974, On Microtus (AI/ophaiomys) deucalion (Kretzoi, 

1969), (Arvicolidae, Rodentia), from the upper Villanyian 

(lower Pleistocene) of Villany-5, S. Hungary: Nederlandse Akademie van Wetenschappen (Koninklijke)-

Amsterdam, Proceedings, Series B, v. 77, p. 259-266. 

___ 1978, Microtus and Pitymys (Arvicolidae) from 

Cumberland Cave, Maryland, with a comparison of some 

New and Old World species: Carnegie Museum Annals, 

v. 47, p. 101-145. 

Miller, G.S., 1912, Catalogue of the mammals of western 

Europe: British Museum (Natural History), 1019 p. 

Nelson, R.S., and Semken, H.A., 1970, Paleoecological and 

stratigraphic significance of the muskrat in Pleistocene 

deposits: Geological Society of America Bulletin, v. 81, 

p. 3733-3738. 

Paulson, G.R., 1961, The mammals of the Cudahy fauna: 

Michigan Academy of Science, Arts, and Letters Papers 

XLVI, p. 127-153. 

Repenning, C.A., 1968, Mandibular musculature and the origin 

of the Subfamily Arvicolinae (Rodentia): Acta Zoologica 

Cracoviensia, v. XIII, p. 29-72. 

___ 1978, Faunal exchanges between Siberia and North 

America: American Quaternary Association, Abstracts, 

fifth biennial meeting, Edmonton, p. 40-55. 

___ 1980, Faunal exchanges between Siberia and North 

America: Canadian Journal of Anthropology, v. 1, 

p. 37-44. 

__ 1983, Pitymys meadensis Hibbard from the Valley of 

Mexico and the classification of North American species 

of Pitymys (Rodentia:Cricetidae): Journal of Vertebrate 

Paleontology, v. 2, p. 471-482. 

___ 1984, Quaternary rodent biochronology and its correlation with climatic and magnetic stratigraphies, in Mahaney, 

W.C., ed., Correlation of Quaternary chronologies: Norwich, GeoBooks, p. 105-118. 

___ 1987, Biochronology of the microtine rodents of the 

United States, Chapter 8 in Woodburne, M.O., ed., Cenozoic mammals of North America-Geochronology and 

biochronology: Berkeley, University of California Press, 

p. 236-268. 

_in press, The fossil record of Arborimus and 

Phenacomys, Chapter 2 in Johnson, M.L., and Maser, 

28 Microtine Rodents, Hamilton Cave, West Virginia 

Chris, eds., Tree voles of the Old Growth Forest: American 

Society of Mammalogists Special Publication. 

Repenning, C.A., Brouwers, E.M., Carter, L.D., Marincovich, 

Louie, Jr., and Ager, T.A., 1987, The Beringian ancestry 

of Phenacomys (Rodentia: Cricetidae) and the beginning 

of the modern Arctic Ocean Borderland biota: U.S. Geological Survey Bulletin 1687, 31 p. 

Repenning, C.A., and Fejfar, Oldrich, 1977, Holarctic correlation of microtid rodents, in Sibrava, Vladimir, ed., Project 73-1-24 "Quaternary glaciations in the Northern 

Hemisphere," Report No. 4, Session in Stuttgart: lUGSUNESCO ICP, Prague, p. 234-250. 

Richmond, G.M., and Fullerton, D.S., 1986, Summation of 

Quaternary glaciations in the United States of America: 

Quaternary Science Reviews, v. 5, p. 183-200. 

Rogers, K.L., Repenning, C.A., Forester, R.M., Larson, E. E., 

Hall, S.A., Smith, G.S., Anderson, Elaine, and Brown, 

T.J., 1985, Middle Pleistocene (Late Irvingtonian) climatic 

changes in south-central Colorado: National Geographic 

Research, v. 1, p. 535-563. 

Sher, A.V., Kaplina, T.N., Kouznetsov, Yu.V., Virina, E.I., 

and Zazhigin, V.S., 1979, Late Cen~zoic of the Kolyma 

Lowland: XIV Pacific Science Congress, Tour Guide XI, 

Academy of Sciences U.S.S.R., Moscow, 115 p. 

Stirton, R.A., 1951, Principles in correlation and their application to late Cenozoic Holarctic continental mammalian 

faunas: International Geological Congress, Report of the 

18th Session, Great Britain, 1948. pt. II, p. 74-84. 

Suchov, V.P., 1976, Remains of lemmings in the Bashkirian 

Pliocene deposits: Academy of Sciences U.S.S.R., Proceedings of the Zoological Institute, v. 66, p. 117-121. [In 

Russian.] 

Wilson, R.W., 1934, A rodent fauna from later Cenozoic beds 

of southwestern Idaho: Carnegie Institution of Washington 

Contributions to Paleontology 440, p. 119-135. 

Wood, H.E., 2nd, Chaney, R.W., Clark, John, Colbert, E.H., 

Jepsen, G.L., Reeside, J.B., Jr., and Stock, Chester, 1941, 

Nomenclature and correlation of the North American continental Tertiary: Geological Society of America Bulletin, 

v. 52, p. 1-48. 

Zakrzewski, R.J., 1972, Fossil microtines from the late Cenozoic 

deposits in the Anza-Borrego Desert, California, with a 

description of a new subgenus of Synaptomys: Natural 

History Museum, Los Angeles County, Contributions in 

Science 221, 12 p. 

Zazhigin, V.S., 1980, Late Pliocene and Anthropogene rodents 

of the south of western Siberia: Academy of Sciences 

U.S.S.R., Transactions 339, 156 p. [In Russian.] 

Zheng, Shaohua, and Li, Chuankui, 1986, A review of Chinese 

Mimomys: Vertebrata PalAsiatica, v. XXIV, p. 81-109. 

_in press, Comments on fossil arvicolids of China, in 

Fejfar, Oldrich, and Heinrich, Wolf-Dieter, eds., International Meeting, evolution, phylogeny, and biostratigraphy 

of arvicolids (Rodentia, Mammalia): Geological Survey of 

Czechoslovakia, Praha. 
INDEX 

[Major page references in italic] 

A 

Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 

Age of the fauna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

a/bipes, Arborimus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

Phenacomys .................................. 1, 7, 9, 10 

(Paraphenacomys) ............................. 9, 10 

Allophaiomys ........................ 4, 10, 12, 14, 15, 16, 17 

diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

inclusion in Arvicolini . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

similarity to Arvicola . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

deucalion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

guildayi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

pliocaenicus ........................ 1, 2, 5, 11, 14, 18, 27 

annectens, Ondatra ................................. 1, 18, 19 

anzaensis, Mictomys . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . 22 

aratai, Pitymys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 

Aratomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

Arborimus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

a/bipes ......... ; . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

longicaudus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

(Arborimus), Phenacomys .............................. 8, 26 

longicaudus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

Aries fauna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

Arvicola ........................................... 4, 10, 26 

different from M. richardsoni . . . . . . . . . . . . . . . . . . . . . . . . . 11 

Arvicolinae, subfamily . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 

diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 

Arvicolin:i, tribe ................................. 3, 4, 11, 18 

diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 

Atopomys sa/velinus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

australis, Synapt{)mys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 

B 

bedjordi, Proedromys .................................... 12 

Bedford's vole ........................................... 12 

Beteke fauna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

borealis, Mictomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22, 23 

Synaptomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 

Borsodia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

brachyodus, Phenacomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 

(Paraphenacomys) ................................ 10, 26 

brandti, Lasiopodomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 14, 16 

brandtoides, Lasiopodomys ............................... 12 

c 

Cape Deceit fauna ......•................................ 14 

carruthersi~ Neodon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 

Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 

Clethrionomyini . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 

cooperi, Synaptomys ................................ 2, 19, 22 

(Synaptomys) . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . 20 

Cosomys ................................................ 4 

Cricetidae . _ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 

Cromeromys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

intermedius . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

(Cromeromys), Mimomys ............................ 4, 6, 26 

considered a Subgenus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

gansunicus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

irtyshensis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

tornensis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

virginianus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

Cseria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

Cudahy fauna ................................. 15, 16, 19, 27 

Cumberland Cave fauna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 

cumberlandensis, Pitymys ................................. 16 

D,E 

deceitensis, Lasiopodomys .................... 1, 12, 14, 15, 26 

Microtus ............................................ 14 

deeringensis, Phenacomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

(Phenacomys) ........................................ 10 

deucalion, Allophaiomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

Dicrostonychinae ................................... 3, 18, 19 

Dixon fauna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 

Dolomys ................................................ 18 

El Casco fauna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19, 21 

F 

Fauna 

Age, Cheetah Room fauna .......................... 2, 16 

Aries ............................................... 11 

Beteke . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

Cape Deceit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 

Cudahy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15, 16, 19, 27 

Cumberland Cave ...........................•........ 19 

Dixon .............................................. 20 

El Casco . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19, 21 

Fyllan Cave . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 20 

Gongwangling ....................................... 12 

Grand View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20, 22, 23, 24 

Hanover Quarry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

Hansen Bluff ............................... 2, 15, 16, 26 

Java ···················-························ 11, 19 

Kamyk ..•........................................ 5, 11 

Kentuck ............................................. 11 

Kudun ......................•....................... 14 

Old Crow Basin, Loc. 47 . . . . . . . . . . . . . . . . . . . . 7, 12, 14, 15 

Osztramos-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

Rebielice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 

Simbugino . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 

Smith Creek Cave ................................. 9, 10 

Snowville ........................................ 23, 24 

Sunbrite Ash Pit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 

Wathena ............................................ 11 

W ellsch Valley . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11, 15 

Williston . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 

Fyllan Cave fauna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 20 

Index 29 
G 

gansunicus, Ali~no~nys .................................... 4 

( Cro~nero~nys) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

Gongwangling fauna ..................................... 12 

Grand View fauna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20, 22, 23, 24 

gryci, Phenaco1nys .................................. 7, 9, 10 

(Paraphenaco~nys) .................................... 10 

guatae~nalensis, Herpeto~nys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 

guildayi, Allophaio~nys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

Alicrotus (Pedo~nys) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

H-J 

Hanover Quarry fauna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

Hansen Bluff fauna and faunal sequence .......... 2, 15, 16, 26 

Heather voles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

Herpeto~nys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15, 16 

guatae~nalensis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I6 

hibbardi, Pity~nys ......................... 1, 2, 14, 16, 17, 27 

Hibbardo~nys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

idahoensis, Ondatra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18, 19 

inter~nedius, Cromero~nys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

AlilnOinYS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

Phenaco~nys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

(Phenaco~nys) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

irene, Neodon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I7 

irtyshensis, Ali~no~nys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

(Cro~nero1nys) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

/schylnolnys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

Java fauna ........................................... II, 19 

John Guilday Cave Preserve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I 

K 

Kamyk fauna ......................................... 5, 11 

kansasensis, Alicto~nys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2I, 22, 23 

(Kentucko~nys) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 

Kata~nys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

Kentuck fauna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I1 

Kentucko~nys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 

(Kentucko~nys), Alicto1nys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 

kansasensis, Alicto~nys ... ............................. 23 

Kis/angia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

Kudun fauna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I4 

L 

Lagurini . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 

landesi, Alicto~nys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 

Lasiopodo~nys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 12 

diagnosis ............................................ I2 

brandti . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I2, 14, I6 

brandtoides .......................................... 12 

deceitensis .............................. 1, 12, 14, I5, 26 

praebrandti ...................................... 12, 14 

Lemminae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3, 19 

diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I9 

Lemmini . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19, 25 

Le~n~nus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19, 25 

longicaudus, Arbori~nus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

Phenaco~nys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7, 8 

(Arbori1nus) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

Loupo~nys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

M 

~ncknowni, Pity~nys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 

~neadensis, Pity~nys ................................... 15, 16 

30 Microtine Rodents, Hamilton Cave, West Virginia 

Pliopota~nys ......................................... 18 

Meadow mice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 

~neltoni, Alicto~nys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22, 23 

Metaxyo~nys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19, 20 

(Metaxyo~nys) vetus, Micto1nys . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 

Synapto~nys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 

"Microtine" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 

Microtini .................................... 3, 4, 11, 14, 16 

diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1I 

Alicrotus ................................... 2, 11, I2, 14; I6 

diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I4 

deceitensis ........................................... 14 

oecono1nus .......................................... 15 

operarius . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 

oregoni . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14, I5 

paroperarius .......................... 1, 2, 14, 15, 16, 26 

pennsylvanicus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I5 

richardsoni . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

xanthognathus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

(Pedomys) guildayi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

Alicto~nys ............................... 1, 19, 22, 23, 25, 27 

diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 

anzaensis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 

borealis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22, 23 

kansasensis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21, 22, 23 

landesi .............................................. 22 

1neltoni . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22, 23 

vetus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22, 23, 26 

(Kentucko~nys) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 

kansasensis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 

(Aietaxyo~nys) vetus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 

(Aiicto~nys) sp., Synapto~nys ............................... 23 

~ni~no~nifor~nis, Pliocto1nys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 

Synapto~nys (Pliocto~nys) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 

AlilnOinYS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I' 4, 11 

diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

gansunicus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

inter~nedius . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

irtyshensis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

~nonohani . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4, 5 

newtoni . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

savini . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4, 11 

tornensis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I, 4 

virginianus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

(Cro~nero~nys) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4, 6, 26 

gansunicus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

irtyshensis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

tornensis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

virginianus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

(Aii~no~nys) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 

(AiilnOinYS), MilnOinYS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 

Alilno!nys Kante . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4, 6 

~nonohani, Ali~no~nys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4, 5 

Muskrats ................................................ 18 

Myopus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19, 25 

N,O 

nebraskensis, Ondatra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

ne~noralis, Pity~nys ............... ~ . . . . . . . . . . . . . . . . . . . . . . . 16 

Neodon ............................................. 14, 16 

carruthersi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 

irene ............................................... . 

Neofiber ............................................... . 

newtoni, Mi~no~nys ...................................... . 

Northern bog lemmings .................................. . 

I7 

18 

4 

22 

ochrogaster, Pity1nys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I6, 17, 27 

oecono~nus, Microtus ..................................... 15 
Ogmodontomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

Old Crow Basin, Loc. 47 ........................ 7, 12, 14, 15 

Ondatra ................................................. 18 

diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

annectens ...................................... 1, 18, 19 

idahoensis ....................................... 18, 19 

nebraskensis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

zibethicus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

Ondatrinae ........................................ 3, 18, 19 

diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

Ondatrini . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

diagnosis ............................................ 18 

operarius, Microtus ...................................... 15 

Ophiomys ............................................... 4 

oregoni, Microtus ..................................... 14, 15 

Orithriomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15, 16 

umbrosus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 

Osztramos-3 fauna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

p 

Paraphenacomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7, 8 

(Paraphenacomys) a/bipes, Phenacomys .................. 9, 10 

brachyodus, Phenacomys . . . . . . . . . . . . . . . . . . . . . . . . . . 10, 26 

gryci, Phenacomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

paroperarius, Microtus ..................... 1, 2, 14, 15, 16, 26 

Pedomys ................................................ 16 

(Pedomys) guildayi, Microtus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

pennsy/vanicus, Microtus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 

Phaiomys ......................................... 4, 11, 16 

Phenacomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 2, 4, 5, 7, 8 

diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

subgenera . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

albipes ....................................... 1, 7, 9, 10 

brachyodus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 

deeringensis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

gryci ........................................... 7, 9, 10 

intermedius . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

longicaudus ......... ~· . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7, 8 

n. sp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

(Arborimus) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 

diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

longicaudus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

(Paraphenacomys) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

albipes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10 

brachyodus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10, 26 

gryci ............................................ 10 

(Phenacomys) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

deeringensis ..................................... 10 

intermedius . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

(Phenacomys), Phenacomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

(Phenacomys) deeringensis, Phenacomys . . . . . . . . . . . . . . . . . . . . 10 

intermedius, Phenacomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

Pine voles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 

pinetorum, Pitymys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16, 17, 27 

Pitymyini ....................................... 3, 4, 11, 16 

diagnosis ............................................ 16 

Pitymys ................................. 2, 11, 12, 14, 15, 16 

diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 

aratai ............................................... 16 

cumberlandensis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 

hibbardi ............................. 1, 2, 14, 16, 17, 27 

diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 

mcknowni . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 

meadensis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15, 16 

nemoralis ........................................... 16 

ochrogaster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16, 17, 27 

pinetorum, and species group . . . . . . . . . . . . . . . . . . . 16, 17, 27 

quasiater, and species group ....................... 16, 26 

savii ................................................ 17 

pliocaenicus, Allophaiomys . . . . . . . . . . . . . . 1, 2, 5, 11, 14, 18, 27 

Plioctomys ................................ 19, 22, 24, 25, 27 

mimomiformis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 

rinkeri ................................ 20, 22, 25, 26, 27 

(Plioctomys) mimomiformis, Synaptomys . . . . . . . . . . . . . . . . . . . 26 

Pliolemmus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 

Pliomyini . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

Pliomys ................................................. 18 

Pliopotamys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

meadensis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

praebrandti, Lasiopodomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 14 

Proedromys ...................................... 12, 14, 15 

diagnosis ............................................ 12 

bedjordi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 

Prometheomyinae .................................. 3, 19, 25 

Promimomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

Q-S 

quasiater, Pitymys .................................... 16, 26 

Rebielice fauna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 

richardsoni, Microtus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

rinkeri, Plioctomys ......................... 20, 22, 25, 26, 27 

Synaptomys ......................................... 19 

(Synaptcmys) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 

salve/in us, A topomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . 1 

savii, Pitymys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 

savini, Mimomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4, 11 

Simbugino fauna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 

Smith Creek Cave fauna ................................ 9, 10 

Snowville fauna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23, 24 

Southern bog lemmings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . 22 

Specimen locations by institution . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

Subgenera 

Arborimus ......................................... 7, 8 

Cromeromys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

Kentuckomys ................................. 19, 23, 24 

Metaxyomys . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . 19, 23 

Mictomys ........................................ 19, 23 

Paraphenacomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

Phenacomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

Plioctomys ....................................... 19, 26 

Synaptomys ......................................... 19 

Sunbrite Ash Pit locality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 

Synaptomyini ............................................ 19 

diagnosis ............................................ 19 

Synaptomys .................................... 1, 19, 22, 27 

diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 

australis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 

borealis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 

cooperi ........................................ 2, 19, 22 

rinkeri .............................................. 19 

vetus ............................................ 20, 21 

(Metaxyomys) vetus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 

(Mictomys) sp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 

(Plioctomys) mimomiformis . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 

(Synaptomys) cooperi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 

rinkeri .......................................... 20 

(Synaptomys) cooperi, Synaptomys . . . . . . . . . . . . . . . . . . . . . . . . . 20 

rinkeri, Synaptomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 

T-Z 

Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

Index 31 
Tjanshanomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

tornensis, Mimomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 4 

(Cromeromys) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

Transbaikalian vole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 

Tyrrhenicola ............................................. 16 

umbrosus, Orithriomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 

vetus, Mictomys . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . 22, 23, 26 

(Metaxyomys) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 

Synaptomys ...................................... 20, 21 

(Metaxyomys) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 

32 Microtine Rodents, Hamilton Cave, West Virginia 

Vi/lanyia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

virginianus, Mimomys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

( Cromeromys) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

Volunteer workers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 

Wathena fauna .......................................... 11 

Wellsch Valley fauna .................................. 11, 15 

Williston fauna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 

xanthognathus, Microtus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

zibethicus, Ondatra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

* U.S. GPO: 1989 673-047 /ai028 
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