Title: Fossil mammals of the coleman ILA local fauna, Sumter County, Florida
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Title: Fossil mammals of the coleman ILA local fauna, Sumter County, Florida
Physical Description: xi, 184 leaves. : illus. ; 28 cm.
Language: English
Creator: Martin, Robert A ( Robert Allen )
Publication Date: 1969
Copyright Date: 1969
 Subjects
Subject: Mammals, Fossil   ( lcsh )
Mammals -- Florida -- Sumter County   ( lcsh )
Zoology thesis Ph. D
Dissertations, Academic -- Zoology -- UF
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Thesis: Thesis -- University of Florida.
Bibliography: Bibliography: leaves 172-183.
General Note: Mauscript copy.
General Note: Vita.
 Record Information
Bibliographic ID: UF00098409
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: alephbibnum - 000572302
oclc - 13780804
notis - ACZ9446

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FOSSIL MAMMALS OF THE COLEMAN IIA

LOCAL FAUNA, SUMTER COUNTY, FLORIDA














By
ROBERT ALLEN MARTIN













A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF
THE UNIVERSITY OF FLORIDA
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE
DEGREE OF DOCTOR OF PHILOSOPHY







UNIVERSITY OF FLORIDA















ACKNOWLEDGMENTS


Thanks go to numerous colleagues who have generously loaned me

both fossil and Recent specimens of Sigmodon and other mammals, or who

have allowed me to view collections in their care, and most are noted

in the Abbreviations section after the institution with which they are

affiliated. I thank especially Dr. and Mrs. Robert Miller and Dr. and

Mrs. Robert Hoffmann for allowing me to live in their homes while on a

recent museum tour. I remain greatly indebted to my parents, Mr. and

Mrs. Gerald M. Martin, for constant encouragement and funds.

This research was supported in part by N. I. H. and N. S. F.

summer fellowships (1966, 1967), a small grant from the Society of the

Sigma Xi, and a small allotment from the Department of Zoology, Univer-

sity of Florida.















TABLE OF CONTENTS

Acknowledgments ---------------------------------------------- ii
List of Tables ----------------------------------------------- v
List of Figures ---------------------------------------------- vii
Description of Measurements and Abbreviations --------------- ix

Introduction ------------------------------------------------ 1
Species List ------------------------------------------------ 8
Species Account --------------------------------------------- 9
Class Mammalia
Order Marsupialia
Didelphis marsupialis ------------------------------ 9
Order Insectivora
Cryptotis parva ------------------------------------ 9
Blarina brevicauda --------------------------------- 9
Scalopus aquaticus --------------------------------- 11
Order Chiroptera
Myotis cf M. austroriparius ------------------------ 11
Pipistrellus subflavus ----------------------------- 11
Plecotus rafinesquii ------------------------------- 12
Order Edentata
+Dasypus bellus ------------------------------------- 13
+Holmesina septentrionalis -------------------------- 16
Order Lagomorpha
Lepus alleni --------------------------------------- 19
Sylvilagus sp. ------------------------------------- 21
Order Rodentia
Sciurus carolinensis ------------------------------- 24
Glaucomys sp. -------------------------------------- 24
Geomys cf G.-pinetis--------------------------------- 33
Reithrodontomys humulis ---------------------------- 33
Peromyscus floridanus ------------------------------ 33
Ochrotomys nuttalli -------------------------------- 34
Peromyscus sp. ------------------------------------- 34
+Sigmodon baker, new species ----------------------- 35

Key to the Extinct and Extant Species of Sigmodon --- 40
Account of the Extinct and Extant Species of Sigmodon 42

Genus Sigmodon --------------------------------- 42
hispidus species group ------------------------- 42
Sigmodon hispidus --------------------------- 42
Sigmodon alleni ----------------------------- 44
Sigmodon ochrognathus ----------------------- 44










TABLE OF CONTENTS continued


Sigmodon fulviventer -------------------------- 44
+Sigmodon baker ------------------------------- 44
leucotis species group --------------------------- 45
Sigmodon leucotis ----------------------------- 45
Sigmodon peruanus ----------------------------- 45
+Sigmodon curtisi ------------------------------ 46
+Sigmodon hudspethensis ------------------------ 47
alstoni species group ---------------------------- 48
Sigmodon alstoni ------------------------------ 48
+medius species group ----------------------------- 48
+Sigmodon medius ------------------------------- 48
+Sigmodon medius medius, new subspecies ---- 50
+Sigmodon medius hibbardi, new subspecies -- 50
+Sigmodon medius, subspecies indeterminate -- 51
+Sigmodon minor -------------------------------- 52
Evolution in the Genus Sigmodon ---------------------- 52
I. Dental Evolution from Pliocene to Recent Time 54
II. Ecological Consideratiods --------------------- 63
III. Fossil Material Examined --------------------- 64
+Pitymys arata, new species --------------------------- 81
Neofiber alleni -------------------------------------- 88
Erethizon dorsatum ----------------------------------- 93
+Hydrochoerus ----------------------------------------- 98
Order Carnivora
+Arctodus pristinus ----------------------------------- 98
Spilogale putorius ----------------------------------- 99
Conepatus sp. ---------------------------------------- 99
Mephitis mephitis ------------------------------------ 99
Procyon cf. P. lotor --------------------------------- 100
+Urocyon minicephalus, new species -------------------- 101
Canis lupus ------------------------------------------ 102
Felis onca ------------------------------------------- 109
Felis rufus ----------------------------------------- 121
Order Artiodactyla
+Platygonus cumberlandensis --------------------------- 127
+Mylohyus sp. ---------------------------------------- 129
+Tanupolama cf. mirifica ------------------------------ 142
Odocoileus virginianus ------------------------------- 143
Order Perissodactyla
+Equus sp. ------------------------------------------ 143
Order Proboscidea
+Mammuthus sp. ---------------------------------------- 144

Age and Correlation ------------------------------------------- 153
Affinities of the Coleman IIA Mammals ------------------------- 159
Paleoecology -------------------------------------------------- 167
Summary and Conclusions --------------------------------------- 170
Literature Cited ---------------------------------------------- 172
Biographical Sketch ------------------------------------------- 184















LIST OF TABLES


1. Measurements (in mm) of lower dentition and mandible
of Recent and fossil Blarina brevicauda and Cryptotis
parva ----------------------------------------------------- 10

2. Distance (in mm) from anterior border of canine alveolus
to posterior border of M3 alveolus in select fossils
and Recent specimens of Myotis ---------------------------- 12

3. Measurements (in mm) of some fossil and living
rabbit femora --------------------------------------------- 20

4. Measurements (in mm) of mandibles and postcranial elements
of Recent and fossil Sciurus niger and S. carolinensis ------ 26

5. Measurements (in mm) of mandibles of Recent and fossil
Glaucomys sabrinus and Glaucomys volans -------------------- 32

6. Measurements (in mm) of lower dentition and mandible
in living and extinct species of Sigmodon ------------------ 69

7. Measurements (in mm) of the lower dentition and
mandible of Sigmodon samples from the Vallecito
Creek-Fish Creek beds -------------------------------------- 79

8. Statistical comparison of Sigmodon samples from
the Wendell Fox Pasture (WFP) and Rexroad Loc.
3 (R3) deposits ------------------------------------------ 80

9. Mandibular dimensions (in mm) of some Recent and
fossil samples of the genera Microtus and Pitymys ---------- 91

10. Measurements (in mm) of skunk mandibles ------------------- 100

11. Measurements (in mm) of fossil and Recent
fox skulls ------------------------------------------------ 105

12. Measurements (in mm) of upper fourth premolar and
upper first molar in fossil and Recent wolves -------------- 116

13. Measurements (in mm) of fossil and Recent
wolf skulls ----------------------------------------------- 118











LIST OF TABLES -continued


14. Measurements (in mm) of the lower dentition of some
extinct and living cats --------------------------------- 124

15. Measurements (in mm) of the lower dentition of fossil
and Recent jaguars --------------------------------------- 126

16. Measurements (in mm) of fossil dental samples of
Platygonus ---------------------------------------------- 131

17. Tanupolama ("short-limbed" species): measurements
(in mm) of metapodials ---------------------------------- 151

18. Tanupolama ("long-limbed" species); measurements
(in mm) of metapodials ---------------------------------- 152

19. Relationships of Coleman IIA mammals --------------------- 165














LIST OF FIGURES


1. The major Pleistocene local faunas of Florida ------------- 5

2. Scatter diagram relating Dasypus bellus to Dasypus

novemcinctus when depth of the movable dermal plates

is plotted against width of these plates ------------------- 15

3. Femora of Lepus alleni (UF 13178; right) and

Sylvilagus sp. (UF 13176; left) from Coleman IIA ----------- 24

4. Scatter diagram relating Glaucomys sabrinus

(large circles) to G. volans (small circles) when

RA length is plotted against MA length --------------------- 31

5. Lower teeth of some fossil and Recent cricetid rodents ----- 38

6. A possible phylogeny for the rodent genus Sigmodon ---------- 58

7. Correlation of Kansas and Arizona deposits containing

members of the medius species group of Sigmodon. ----------- 60

8. Composite ratio diagram of measurements of the

lower dentition and mandible in some members of the

Sigmodon medius species group from Kansas and

Arizona --------------------------------------------------- 62

9. The dentition of Pitymys arata and Equus sp. from

the Coleman IIA fauna and femora of Lepus alleni

and Lepus townsendii --------------------------------------- 90

10. Upper dentition of fossil porcupine, UF 11774,

from Coleman IIA ------------------------------------------- 97










LIST OF FIGURES continued


11. Recent and fossil skulls of foxes ---------------------- 104

12. Skulls of Canis lupus from Coleman IIA ---------------- 111

13. Ventral view of skull of Canis lupus from Coleman

IIA (UF 11519) ---------------------------------------- 113

14. Scatter diagram relating Pleistocene and Recent

wolves when the length of the P4 (X axis) is plotted

against the width of the P4 (Y axis) ------------------- 115

15. Ratio diagram comparing the lower dentitions of

various felines ---------------------------------------- 123

16. Palate and partial skulls of Platygonus

cumberlandensis from Coleman IIA -----------------------

17. Scatter diagram relating various samples of

fossil Platygonus when length of the MI (X axis) is

plotted against the width of the M1 (Y axis) ------------ 141

18. Labial view of the lower dentition and mandible

of Tanupolama from Coleman IIA (UF 11985) ------------- 146

19. Occlusal view of lower dentition and mandible of

Tanupolama from Coleman IIA (UF 11983) ---------------- 148

20. Regression analysis relating two species of

camels from the Pleistocene of Florida when proximal

width of the metapodial (X axis) is plotted against the

greatest length of the metapodial (Y axis) ------------ 150

21. Replacement of mammals in Florida during the

Pleistocene ------------------------------------------- 158















MEASUREMENTS AND ABBREVIATIONS


I. Measurements

Sciurus and Glaucomys

Innominate length greatest length

Innominate width greatest width with the calipers held

perpendicular to the long axis of the

innominate

Femur length greatest length

Femur width (distal) distance between the medial and

lateral condyles

Tibia length greatest length

Tibia width proximall) distance between the medial and

lateral condyles

Humerus length greatest length

Humerus width proximall) distance between the greater and

lesser tuberosities

MA length mandibular alveolar length

RA length ramus alveolar length; distance from the greatest

angle of the posterior border of the ascending ramus

to the anterior border of the alveolus of the first

lower molar (see Martin, 1967)

Cryptotis and Blarina

Condyloid to mental foramen distance from the most posterior

projection of the condyloid process

to the center of the mental foramen

ix










Cryptotis and Blarina continued

Condyloid to M1 distance from the most posterior projection of

the condyloid process to the anterior border

of M1

Sigmodon

Length M3 the entire visible length of the tooth in occlusal

view; not merely the occlusal surface

Width M1, M2, M3- the entire visible width of the teeth in occlusal

view; not merely the occlusal surface

Canis

Width P and MI taken by first placing one edge of the calipers

flush with the labial border of the paracone and

metacone, then bringing the other ediege into

contact with the protocone



All multiple tooth measures designated by letters (e. g., M M2)

are measurements taken from the anterior border of the first tooth to

the posterior border of the second, inclusive; each is not measured

separately.

Measurements were taken with a Helios 7-inch calipers and a

Gaertner platform measuring microscope.

A cross (+) preceding the name of a taxon indicates that it is

extinct.



II Abbreviations

UF University of Florida, Florida State Museum (Walter Auffenberg,

S. David Webb, Thomas Patton)










FGS Florida Geological Survey (Stanley Olsen)

FDT Florida Diving Tours

UT or UTMM University of Texas, Texas Memorial Museum (Ernest Lundelius,

Jr.)

UMMVP University of Michigan Museum,Vertebrate Paleontology (Claude

Hibbard)

LACM Los Angeles County Museum (Theodore Downs, John White)

UAVP University of Arizona, Vertebrate Paleontology (Everett Lindsay)

MUVP Midwestern University, Vertebrate Paleontology (Walter Dalquest)

UKMVP University of Kansas Museum, Vertebrate Paleontology (Theodore

Eaton, Orville Bonner)

UK University of Kansas Museum, Natural History (J. Knox Jones, Robert

Hoffmann)

UCMVP University of California at Berkeley Museum, Vertebrate

Paleontology (Donald Savage)

UCMVZ University of California at Berkeley, Museum of Vertebrate

Zoology (William Lidicker)

AMNH American Museum of Natural History (Richard Tedford, Malcolm

McKenna, Richard Van Gelder, Sydney Anderson, Guy Musser)

USNM United States National Museum (Clayton Ray, Nicholas Hotton,

Charles Handley, Henry Setzer, Ronald Pine, John Paradiso)















INTRODUCTION


Florida has produced, and still continues to produce, some of the

richest Pleistocene deposits in the world. Yet these deposits have,

until very recently, defied interpretation. This is particularly true

of the mammalian faunas; less so of some of the reptilian faunas.

Auffenberg's (1958) study of the genus Terrapene is the only published

attempt to correlate the numerous isolated Florida deposits both in time

and in relation to major eustatic changes in sea level. However, of

those Pleistocene faunas considered by Auffenberg (1958), only six--

Vero (Weigel, 1962), Williston (Holman, 1959), Sabertooth Cave (Simpson,

1928), Seminole Field (Simpson, 1929), Reddick IA (Gut and Ray, 1963),

and Melbourne (Ray, 1958)--had been studied in any detail with respect

to their mammalian component. In addition, Brooks (1968) presented evi-

dence that some of the ancient shorelines considered by Auffenberg (1958)

to be of Pelistocene age are probably much more archaic. Nonetheless,

my studies of the Florida Pleistocene mammalian faunas confirm most of

Auffenberg's conclusions regarding the chronological ordering of these

faunas.

The Coleman IIA local fauna represents a particularly important,

previously unsampled, time period in Florida's history, and has provided

the information necessary to develop a coherent picture of mammalian

turnover in Florida during the Ice Ages (Pleistocene). Therefore it

seems reasonable to familiarize the reader with those other Florida






-2-


Pleistocene faunas which I will constantly mention in the text. The fol-

lowing is a list of these faunas. Exact locations and geologic setting

are given only if not previously described. All localities are mapped

in Figure 1 and the numbers preceding the localities refer to their

location on the latter map:


2) Ichetucknee River, Columbia County (Simpson, 1930; Auffenberg, 1963;

Kurten, 1965; McCoy, 1963; Martin, 1969a)

3) Santa Fe River, Gilchrist County (Martin, 1969a)

Localities 1, 1B, 2, 4A, 8A

6) Haile, Alachua County (Brodkorb, 1953; Auffenberg, 1963; Ligon, 1965)

Localities VIIA, VIIIA, XIA, IXB, XIIIA, XIIIB, XIIIC,

XIVA, XIVB, XVA

4) Arredondo, Alachua County (Bader, 1957; Brodkorb, 1959; Auffenberg,

1963)

Localities IA, IIA, IIB

7) Williston, Levy County (Holman, 1959)

Locality III

8) Devil's Den, Levy County (Arata, 1961; Kurten, 1965)

9) Reddick, Marion County (Brodkorb, 1957; Gut and Ray, 1963)

Localities IA, IB, IIC

13) Sabertooth Cave, Citrus County (Simpson, 1928; Auffenberg, 1963)

11) Withlacoochee River, Citrus County (Martin, 1968a, 1969a)

Locality 7A

20) Eichelberger Cave, Marion County (Auffenberg, 1963)

Localities A and B










18) Bradenton Field and 51st Street, Manatee County (Simpson, 1929;

Auffenberg, 1963)

14) Seminole Field, Pinellas County (Simpson, 1929; Auffenberg, 1963)

5) Payne's Prairie, Alachua County (Auffenberg, 1963; Martin, 1969a)

16) Melbourne, Brevard County (Gazin, 1950; Ray, 1958

star) Coleman, Sumter County

Locality IIA (this report)

Locality III; A, B, C, D: the west wall of Pit III is

composed of a series of superimposed fresh water

marls; the letters stand for four recognizable

spring heads.

15) Pool Branch, Polk County

Fossils from this locality were recovered from a canal

bank east of the Peace River near the Clear Spring

Mine; near the town of Fort Meade.

19) Punta Gords, Charlotte County

Fossils were recovered from the bank of Alligator Creek

in the N edge SW-1/4 NE-1/4 Sec. 26, T 41 S, R

23 E of the Cleveland Quadrangle.

1) Aucilla River, border of Madison and Jefferson Counties

Localities from this river and their mammalian contents

have not been described.

12) Inglis, Citrus County

Locality IA; The fossil material from this local-

ity comes from a limestone sinkhole, filled with

beach sands, exposed on the north bank of the

Florida Barge Canal.
































Figure 1 -- The major Pleistocene local faunas of Florida.

The numbers on the map correspond to the same

numbers preceding the names of the faunas in

the list of localities.













Lime-mining operations provide some of the most productive fossil

localities in Florida. These operations are concentrated on the Ocala

Arch, an uplifted limestone ridge in the center of the state including

formations of Eocene through Pleistocene age. The Coleman IIA fauna

was removed from a filled sinkhole in the Ocala Eocene limestone at the

Dixie Lime and Stone Corporation at Coleman, Sumter County, Florida

(SE-1/4, NW-1/4, Sec. 7, T 20 S, R 23 E; 70-90 feet above present sea

level; Figure 1).

The original Coleman IIA deposit no longer exists; it was com-

pletely destroyed by further mining operations. Mr. Robert Allen, one

of the first collectors at the site, provided me with the following de-

scription of the locality. The sink was approximately 30 yards long and

25 yards wide. Two faces, a wet orange-brown clay and a coarse gray-

white sand, were obvious in this perspective. Although the clay faces

appeared homogeneous, the sand faces was filled with pebble- to boulder-

sized limestone rubble. The bone removed from the clay was usually

colored white or orange, with all gradations in between; the bone from

the gray-white sand was characteristically black, occasionally white.

Bones also transgressed these faces boundaries, and are characteris-

tically colored half orange-brown and half black, testifying to the

contemporaneity of both lithologic units. Wet bone from the sand was

much harder than that from the clay upon initial removal. None of the

bone appears to have been tumbled, and semi-articulated (or at least

closely associated) skeletal materials were removed from both clay and

sand faces. This suggests a lack of transport by water or any other

agent.










An unpublished manuscript of Norm Tessman shows that the long

bones of all species of the large mammals recovered from the Coleman

IIA deposit suffered pre-fossilization breaks. Pre-fossilization breaks,

or "green" breaks, are recognized by their rough and oblique nature and

microscopic evidence of lacunae collapse along the broken surface (Tess-

man compared the fossil bones with some intentionally broken in the lab-

oratory and some known to have accumulated in a Recent sinkhole for con-

firmation of these characteristics). Bone breakage due to post-fossil-

ization phenomena usually can be recognized by the "clean" nature of the

break. Less than 10% of bones demonstrating green breaks also manifested

tooth markings indicative of large carnivore action. These data strongly

suggest that the Coleman IIA deposit was a natural-trap type of sinkhole.

That the sink was quite extensive and not filled to the top with

water during most of its depositional history is shown by the relatively

large quantity of bat remains. Those of Myotis austroriparius are

particularly common, and as this bat dwells now in limestone caves and

sinks in north Florida, we may assume that it also inhabited the more

inaccessible reaches of the Coleman IIA sinkhole. Owl remains have

also been recovered from the sink, and it is conceivable that they also

utilized the cavernous portions for roosting sites, and inadvertently

stockpiled small mammal remains. One may find fossilized owl pellets

at the Reddick IA site, which at least suggests that the phenomenon

is not particularly unusual.










SPECIES LIST
Minimum
% Number
Total Individuals

Didelphis marsupialis 2.0 5

Cryptotis parva 2.4 6
Blarina brevicauda 0.4 1
Scalopus aquaticus 0.8 2

Pipistrellus subflavus 3.6 9
Myotis cf austroriparius 10.4 26
Plecotus rafinesquii 0.8 2
Bat sp. 11.2 28

+Dasypus bellus 0.4 1
+Holmesina septentrionalis 0.4 1

Lepus alleni 2.4 6
Sylvilagus sp. 3.6 9

Sciurus carolinensis 1.6 4
Glaucomys sp. 0.4 1
Geomys cf G. pinetis 4.8 12
Reithrodontomys humulis 2.0 5
Peromyscus floridanus 7.6 19
Peromyscus sp. 11.2 28
Ochrotomys nuttalli 1.2 3
+Sigmodon baker new sp. 4.4 11
+Pitymys arata new sp. 0.8 2
Neofiber alleni 0.4 1
Erethizon dorsatum 0.4 1
+Hydrochoerus sp. ? ?

Canis lupus 1.6 4
+Urocyon minicephalus new sp. 6.8 17
+Arctodus pristinus 0.4 1
Procyon lotor 0.4 1
Spilogale putorius 0.8 2
Mephitis mephitis 0.4 1
Conepatus sp. 0.8 2
+Felis onca augusta 2.8 7
Felis rufus 0.4 1
+Mammuthus sp. 0.4 1
+Equus sp. 0.8 2
+Platygonus cumberlandensis 4.4 11
+Mylohyus sp. 0.4 1
+Tanupolama cf 1. mirifica 2.8 7
Odocoileus virginianus 3.2 8
249










SPECIES ACCOUNT


Class Mammalia

Order Marsupialia

Family Didelphidae

Didelphis marsupialis Allen- opposum

Material: UF 11826-11829; 1 left dentary, 1 left maxilla, 5 right

humeri, 2 left femora, 4 vertebrae.

Remarks: The fossil material is identical to that of Recent D. marsupi-

alis.


Order Insectivora

Family Soricidae

Cryptotis parva (Say)- least shrew

Material: UF 11628-11641; 9 mandibles, 6 maxillae, 1 humerus.

Remarks: Table 1 shows that size differences separate mandibles of C.

parva from those of Blarina brevicauda. There is little overlap in the

measurements even though the series of Blarina measured consisted al-

most exclusively of B. brevicauda minima, the smallest subspecies of

Blarina. In those fossil specimens in which the M3 is present, the

talonid is reduced as in Recent Cryptotis (Hibbard, 1963; Guilday,

1962).


Blarina brevicauda (Say)- shorttail shrew

Material: UF 11626; 1 right mandible.

Remarks: The M3 is not preserved on the fossil, but the size of the

mandible (Table 1) and qualitative characters (after Guilday, 1962)

identify it as B. brevicauda.








-10-


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Family Talpidae

Scalopus aquaticus Linnaeus- eastern mole

Material: UF 11642-11645; 1 right dentary, 2 femora, 3 humeri.

Remarks: The small sample precludes statistical treatment, but the humeri

and toothless dentary agree with the same elements of Recent Scalopus

aquaticus from Florida.


Order Chiroptera

Family Vespertilionidae

Myotis cf M. austroriparius (Rhodes)- south-

eastern myotis

Material: UF 13244, 13245, 13251, 13252, 13256-13292: partial skull,

partial palates and mandibles.

Remarks: Considering the western affinities of a number of the Cole-

man IIA mammals, the possibility that this is a small western species

of Myotis deserves careful consideration. Yet I cannot discern any qual-

itative or quantitative differences between the Coleman Myotis and Re-

cent M. austroriparius from Florida, while size differences tend to

separate it from M. keenii and M. grisescens (Table 2). On the other

hand, I cannot separate the Coleman II Myotis from M. lucifugus.


Pipistrellus subflavus (F. Cuvier)- eastern

pipistrelle

Material: UF 13246-13250, 13253-13255; dentaries and partial palates.

Remarks: The genus Pipistrellus has one less premolar than either

Plecotus or Myotis, and may be separated from other living Florida bats

on the basis of size and dental configuration. The fossil material is

identical to that of Recent P. subflavus from Florida.






-12-


Table 2

Distance (in mm) from anterior border of canine
alveolus to posterior border of M3 alveolus
in select fossils and Recent specimens of Myotis



Coleman IIA Devil's Den


N X O.R. N X O.R.

M. austroriparius 11 5.8 5.5-5.9 6 5.5 5.3-5.9

M. grisescens 7 6.3 6.2-6.6


Indiana, Pennsylvania

M. keenii 10 6.2 6.0-6.6
(Miller and Allen, 1928)





Plecotus rafinesquii Lesson- Rafinesque's

big-eared bat

Material: UF 13240-13243; a partial palate and mandibles.

Remarks: The use of Plecotus rather than Corynorhinus follows Dalquest

(1953) and Handley (1959). The following features may distinguish

dentitions of Plecotus from those of Myotis:

1) Paraconid and metaconid less separated in Plecotus

2) Protoconid higher and more blade-like in Plecotus

3) Only two upper premolars in Plecotus

4) Hypocone on M1-M2 absent in P. rafinesquii (well developed in

all Myotis I have seen from Florida).

The third character is not applicable to the fossil material

available, but the others clearly permit the identification of P.

rafinesquii.










Order Edentata

Family Dasypodidae

+Dasypus bellus (Simpson)- beautiful armadillo

Material: UF 13190, 13191, 13187; dermal plates and an astragulus

Remarks: The fossil Dasypus material includes dermal plates of two size

classes (Figure 2). They may be from two individuals, but most likely

represent samples from two body areas of a single individual. As can be

seen from Figure 2 there is very little overlap in size of the dermal

plates between the extinct Dasypus bellus and the living D. novemcinctus.

The area of overlap includes, in the fossil armadillos, only the small

animal from Coleman IIA and a few plates of animals from other deposits.

Measurements of the fossil and Recent armadillo dermal plates (movable

plates only) are presented below (N = number of plates measured, X =

mean, 0. R. = observed range of measurements):

Thickness Width
N X O.R. N X O.R.
D. novemcinctus 235 1.6 0.9-2.4 235 5.4 3.5-8.1


+D. bellus

Blancan
(Haile XVA)

Irvingtonian
(Coleman IIA)

Rancholabrean
(Haile VIIA, Haile XIB,
Reddick IA, Reddick IB,
Bradenton 51st St.,
Arredondo II, Medford I,
Kendrick I)


10 3.5 2.9-4.2


21 4.0 2.7-6.8


163 3.9 1.9-6.1


10 10.5 8.2-12.4


21 8.2 6.2-10.3


163 11.4 6.6-16.5























Figure 2 -- Scatter diagram relating Dasypus bellus to

Dasypus novemcinctus when depth of the mov-

able dermal plates is plotted against width

of these plates. Large circles denote the

range of measurements in D. novemcinctus,

small circles and circles with lines denote

the range of measurements of D. bellus.

Circles with lines = dermal plates from
1
Coleman IIA, X = grand mean of 235 meas-
2
ured plates of D. novemcintus, X = grand

mean of 194 measured plates of D. bellus.










*











x2
101-5

+





+. +4+
+
0 +
0









xx2
+ *
0 +






5.1- 0
*


1.1 2.1 3.1 4.1 5.1 6.1
DEPTH










+Holmesina septentrionalis (Leidy)- armadillo

Material: UF 13186, 18188, 18189; dermal plates and metapodials.

Remarks: Considering that there are two names in the recent literature

for this animal, and that there are two species (one undescribed; Haile

XVA) of possibly two genera of chlamytheres in Pleistocene deposits from

Florida, a general review of this subject seems worthwhile now. Much of

this discussion is taken from Simpson (1930b).

The first chlamythere record in North America was published by

Leidy (1889 a); the material consisted of dermal plates found in Peace

Creek, Florida, and was referred to Glyptodon, new species septentrionalis.

"Later Leidy (1889 b) recognized that they did not belong to a glyptodont

but to a gigantic armadillo and referred them to Chlamytherium humboldtii

Lund, a species described from cave deposits in Brazil (Simpson, 1930 b)."

Sellards (1915) demonstrated that the Florida chlamythere was a differ-

ent species than C. humboldtii, and referred the Peace Creek material,

and material from Vero, Florida, to Chlamytherium septentrionalis.

Simpson (pers. common.) has pointed out to me that Sellards' use of

septentrionalis was incorrect. As the species name must agree in gender

with the genus to which it is referred, the proper name for referral to

Chlamytherium is septentrionale. Following the taxonomic system of

Castellanos (1927), with new Florida chlamythere fossils from Braden-

ton Field, Simpson (1930 b) referred the Florida chlamythere to a new

genus, Holmesina, species septentrionalis (agreeing in general with

Holmesina, which is feminine).

Some workers since that time (Bader, 1957; Weigel, 1962) have fol-

lowed Simpson's conclusions, but others (James, 1957; Ray, 1958; Gut





-17-


and Ray, 1963; Hibbard and Dalquest, 1966) have reinstated Chlamytherium.

There are presently six named genera of Plio-Pleistocene chlamytheres:

Chlamytherium (=Pampatherium), Plaina, Hoffstetteria, Kraglievichia,

Vassalia, and Holmesina. The first five were originally described from

South American deposits (reviewed by Castellanos, 1927, 1937, 1957), the

last solely from the United States (Simpson, 1930b). Kraglievichia,

Plaina, and Vassalia are Pliocene forms (from Entrerian, Monte Hermosan,

and Araucanian time), and South American Chlamytherium and Hoffstetteria

are restricted by Castellanos to the Pleistocene (Pampean of Argentina

and Brazilian and Ecuadorian deposits presumably of Pleistocene age).

As Simpson (1930b) states, "If . [Chlamytherium, Kraglievichia, and

Vassalia] . be retained in a single genus, then the Florida form

belongs in that genus. If Castellanos is followed, which is probably

preferable . then the Florida species cannot be referred to any

of his three South American genera, for it differs from them as much

as they differ among themselves."

Considering that there is no recent taxonomic revision of these

forms available, Simpson's statements seem to outline the most logical

present course of action regarding the taxonomic status of the Florida

late Pleistocene (Rancholabrean) chlamythere, recorded by Ray (1958)

from Melbourne, Weigel (1962) from Vero, Bader (1957) from Hornsby

Springs, Gut and Ray (1963) from Reddick IA, and by Simpson (1928,

1929, 1930b) from Sabertooth Cave, Bradenton Field, Peace Creek, With-

lacoochee River, Venice, Sarasota, and Seminole Field. The same can-

not necessarily be said of the chlamytheres noted by Hibbard and Dal-

quest (1966) from the middle Pleistocene of Texas, and by Cahn (1922)











and Hay (1926) from deposits of uncertain age in Texas, as there is

evidence that anthoe genus of chlamythere was also present in North

America during part of the Pleistocene.

Castellanos (1927, 1957) and Simpson (1930 b) assumed that a maxi-

mum of three genera of chlamytheres existed during the entire Pleistocene

in both North and South America. Further, only one species of each genus

was recognized during that time (South America, Chlamytherium humboldtii

and Hoffstetteria occidentale; North America, Holmesina septentrionalis).

Recent collecting in Florida directed by S. David Webb has produced a

new, small chlamythere of early Pleistocene (late Blancan) age. This

species is now known from the Haile XIIA, Haile XVA (Robertson, Ph. D.

disser., U. Fla.), and the Santa Fe River 1 (intrusive) and 1B faunas.

The generic status of the Blancan form is not now known; in size and

some features of the dentition the beast probably best approximates

Kraglievichia.

In the Coleman IIA chlamythere the dermal plates and metapodials

are comparable in size to those of Holmesina septentrionalis. This is

the earliest record of this genus in Florida. The following is a list

of localities in Florida, other than those noted previously, that con-

tain remains of Holmesina septentrionalis:

Alachua County:- Arredondo, Pit I (site unknown), Pit II (just S of B);

Haile, Loc. VIIA, VIIIA; and Payne's Prairie, Loc. III.

Calhoun County:- Chipola River, Loc. 2.

Charlotte County:- Charlotte Harbor.

Citrus County:- Withlacoochee River, Loc. 7A.

De Soto County:- Joshua Creek; and Prairie Creek.











Gilchrist County:- Ichetucknee River; and Santa Fe River, Locs. 2, 3,

7B, 11C, 17.

Levy County:- Waccasassa River.

Marion County:- Medford, Cave 1; Orange Springs, Loc. 1; and Reddick IIC.

Orange County:- Rock Springs.

Palm Beach County:- Jupiter Inlet.

Polk County:- Pool Branch.

Sarasota County:- Apollo Beach.

Sumter County:- Coleman III, Locs. B, C.

Suwanee County:- Branford IA.


Order Lagomorpha

Family Leporidae

Lepus alleni Mearns- antelope jackrabbit

Material: UF 13178, 13179; femora and innominates.

Remarks: The Coleman material referrable to the antelope jackrabbit

consists of ten femora and two innominates. All lagomorph dental com-

ponents in the fauna were assignable to Sylvilagus. The femora are

rather large, and most closely approximate the antelope jackrabbit,

Lepus alleni (Table 3; Figure 3). There is some overlap in measure-

ments between L. alleni and L. townsendii, but configuration of the

lesser trochanter and accompanying muscle scars (of the obturators and

quadratus femoralis especially) readily separate these species (Figure

10). Lepus alleni is also a member of the Inglis IA Irvingtonian de-

posit, and its occurrence in these deposits marks the first record of

this genus from Florida.










Table 3

Measurements (in mm) of fossil and living rabbit femora




N X 0. R.

Lepus californicus

Gr. w shaft 9 8.6 7.2-9.5

Gr. length 9 108.2 100.5-114.8

Gr. w distal 9 16.1 15.2-16.8

Gr. w head 9 8.2 7.6-8.9

Lepus townsendii

Gr. w shaft 10 10.1 9.3-10.8

Gr. length 10 123.1 117.7-129.0

Gr. w distal 10 19.0 18.3-20.5

Lepus alleni

Gr. w shaft 6 9.3 8.4-9.8

Gr. length 6 118.9 114.4-122.6

Gr. w distal 6 18.6 18.3-19.3

Gr. w head 6 9.6 8.9-10.1

Lepus americanus

Gr. w shaft 5 6.6 6.0-7.5

Gr. length 5 89.9 84.7-96.7

Gr. w distal 5 12.7 11.7-13.9

Gr. w head 5 6.5 5.9-6.8






-21-


Table 3 (continued)


N X 0. R.

Coleman II Lepus alleni

7 9.0 8.0-10.3

1 118.3

2 17.8 17.6-18.0

3 9.5 9.2-9.7

Coleman II Sylvilagus

3 6.2 6.0-6.5

1 71.4

3 11.2 11.0-11.6

1 5.5


Sylvilagus sp.- marsh and/or


cottontail

rabbit


Material: UF 13158-13161, 13165, 13166, 13174-13177: 3 femora, 6

humeri, 2 scapulae, 4 calcanea, 11 mandibles, 2 tibia, 1 innominate,

5 ulnae, isolated teeth.

Remarks: The material is too poor to be identifiable to species, as

characteristic portions of the mandibles have been shorn away. Both

Sylvilagus floridanus and S. palustris are presently sympatric in Florida,

found in almost every situation providing dense underbrush. Some meas-

urements of the Coleman IIA Sylvilagus are presented in Table 3.


w. shaft

length

w distal

w head



w shaft

length

w distal

w head

























Figure 3 -- Femora of Lepus alleni (UF 13178; right) and
Sylvilagus sp. (UF 13176; left) from Coleman
IIA.
i













I4.










Order Rodentia

Family Sciuridae

Sciurus carolinensis Gmelin- Gray squirrel

Material: UF 11650-11658; 3 innominates, 2 right mandibles, 1 maxilla,

5 femora, 2 humeri, 2 tibia, 2 ulna, 2 incisors.

Remarks: Table 4 shows that in almost all measurements the fossils con-

form to Recent Sciurus carolinensis. Sciurus niger is consistently

larger. The MA length of S. niger shown in Table 4 agrees with the

dentary tooth row measurements presented by Moore (1956) for S. niger

shermani from central Florida.


Glaucomys sp.- flying squirrel

Material: UF 11646-11649; 2 dentaries, 1 femur.

Remarks: Table 5 shows that the Glaucomys fossils are not identifiable

to species when either the MA or RA lengths are considered separately.

This is true also when the MA length is plotted against the RA length

(Figure 4). The one fossil from which both measurements were obtain-

able lies intermediate between the two species.

Guilday, et al. (1964) identified both G. volans and G. sabrinus

from the New Paris No. 4 Sinkhole in Pennsylvania. Although the fossil

G. volans averaged 8% larger than modern samples from Pennsylvania,

overlapping with modern G. sabrinus macrotis in MA length, they felt

that G. volans was larger in the Pleistocene. This interpretation gains

support from the fact that in the same fauna G. sabrinus averaged 13%

larger than Recent Appalachian races of that species.

The Coleman IIA Glaucomys are 8% larger than the average Recent






-25-




G. volans from the southeastern U. S. However, because the MA length

is so variable in G. sabrinus (V = 8.97) and because the theoretical

range of measurements for the MA length of G. sabrinus at 13s includes

the entire theoretical range at t3s for G. volans, the Coleman IIA

Glaucomys must remain unidentified at present.

























"'CO

00

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34






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Figure 4 -- Scatter diagram relating Glaucomys sabrinus

(large circles) to G. volans (small circles)

when RA length is plotted against MA length.

Star = fossil Glaucomys from Coleman IIA.


__







-31-


9.0-





85- *





80- *











to
S7.5- *

S*
**
**
70- **
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8 **
3 433 0

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Si 8 *
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*
6.0- *


10.0 11.0 12.0 13.0 14.0
10.0 11.0 120 13.0 14.0


R.A. LENGTH








-32-


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Family Geomyidae

Geomys cf G. pinetis Rafinesque- southeast-

ern pocket gopher

Material: UF 11659-11683; 1 partial cranium, 10 right mandibles, 8 left

mandibles, 5 left femora, 2 left humeri, 3 right humeri, 4 right innomin-

ates, 4 left innominates, 2 right tibia-fibulae, 12 left upper incisors,

11 right upper incisors, isolated teeth.

Remarks: The fossil specimens are identical to Recent G. pinetis from

Florida. However, they are not certainly unseparable from G. bursarius

and G. personatus either. These three species are obviously closely

related and probably represent remnants of a common Pleistocene Gulf

coast population.


Family Cricetidae

Reithrodontomys humulis (Audubon and Bachman)-

eastern harvest mouse

Material: UF 11686-11695; 8 mandibles, isolated teeth.

Remarks: Reithrodontomys humulis is easily identifiable by the pres-

ence of a distinct labial cingulum, usually with associated cusplets,

on the M1 and M2 (Hall and Kelson, 1959; Hooper, 1952). The grooved

upper incisors are also diagnostic.


Peromyscus floridanus (Chapman)- gopher or

Florida mouse

Material: UF 11731, 11733-11736, 11738-11743, 11746-11747, 11749-11761,

11763-11768; 31 mandibles.

Remarks: Identification of P. floridanus follows Martin (1967). This






-34-


mouse is one of the largest of North American Peromyscus. It is identi-

fiable from the MA length alone. The dental pattern of the fossils agrees

with the description given by Bader (1959), in that the ectolophid and

ectostylid are rare or absent, while on the MI and M2 the mesostylid and

mesolophid are poorly developed or absent.


Ochrotomys nuttalli (Harlan)- golden mouse

Material: UF 11730; 3 humeri (2 left, 1 right), 1 right mandible, 1

right maxilla, 2 isolated molars.

Remarks: 0. nuttalli mandibles without teeth can be separated from other

Recent Florida Peromyscus species when RA length is plotted against MA

length (Martin, 1967). The position of the mental foramen will further

separate 0. nuttalli from some additional Peromyscus species (Martin 1968b),

but identification of toothless mandibles is not possible if either P.

maniculatus or P. leucopus is presumed present in the fossil fauna under

study. Molars of the golden mouse are easily identified. The molar

pattern is one of the most complex of the Peromyscines (Osgood, 1909;

Hooper, 1957; Bader, 1959; Martin, 1968b).

Humeri like those of Peromyscus, lacking an entepicondylar fora-

men, may also be referred to 0. nuttalli. The entepicondylar foramen

is absent in 0. nuttalli and is present in specimens of Peromyscus

polionotus, P. gossypinus, and P. leucopus.


Peromyscus sp.

Material: UF 11720-11729, 11732, 11737, 11744, 11745, 11748, 11762,

11769-11784; 17 left mandibles, 7 right mandibles, 5 right humeri, 8

left humeri, 5 right femora, 10 left femora, 3 right innominates, 3










right tibia-fibulae, 3 left tibia-fibulae, numerous isolated teeth.

Remarks: This material probably represents a mixture of three or four

Peromyscus and Ochrotomys species. It undoubtedly contains some small

P. floridanus, a few specimens of 0. nuttalli (toothless mandibles),

and either one or two of the species P. gossypinus, P. leucopus, or P.

maniculatus. The incidence of accessory cusps increases on the molars

of these smaller mandibles, as they do in P. gossypinus, P. leucopus, and

P. maniculatus. Three mandibles (UF 11720, 11723, 11724) have an MA

length which falls in the range of P. polionotus (fossils: 3.6-3.7mm;

Recent P. polionotus: 3.1-3.7mm), but this length also falls within

the measured range of all southeastern Peromyscus species except P

floridanus (Martin, 1967). Since no mandibles or teeth were identi-

fied as P. polionotus it seems likely that the oldfield mouse is ab-

sent from the Coleman IIA fauna.

Western Peromyscus species, such as P. pectoralis, P. boylii, and

P. eremicus now found in Texas are definitely not represented in Cole-

man IIA (see Martin, 1968b).


+Sigmodon baker, new species

= Sigmodon hispidus, Holman, 1959;

Bull, Florida State Museum, 5(1):1-24

Holotype: UF 11700, a left mandible with all teeth


Horizon and Locality: late Irvingtonian; Coleman IIA, Sumter County,

Florida.


Referred specimens:










Coleman IIA, Sumter County, Florida

UF 11696-11719; 11 left mandibles, 8 right mand-

ibles, 2 left maxillae, 3 left femora, 4 right

femora, isolated teeth.

Bradenton Field, Manatee County, Florida; early Sangamon:

UF 2002; left mandible.

Williston III, Levy County, Florida; early Sangamon:

FGS 5862; 2 left mandibles, 1 right mandible,

1 lower right incisor.

Haile VIIA, Alachua County, Florida; early Sangamon:

UF 9844; right mandible

UF 15153; 2 right mandibles, 1 left mandible,

3 isolated molars.

Diagnosis: The first lower molar of Sigmodon bakeri possesses 4 well

developed roots, indicating alliance with the hispidus species group as

defined on page 42 of this treatment. Sigmodon bakeri differs from all

of these species in characteristically lacking an anterior cingulum on

the M2 and M3 (Figure 5). The configuration of the anteroconid of the

M1 will also separate S. bakeri from other hispidus group species. In

S. bakeri the anteroconid is grossly asymmetrical and is extended lab-

ially and posteriorly. Other hispidus group species will evidence this

character occasionally, but normally the anteroconid is symmetrical or

only slightly asymmetrical. Sigmodon bakeri is smaller than any living

Sigmodon species except S. ochrognathus (Table 6).

Etymology: This species is named after Dr. Rollin Baker of Michigan

State University for his work on living cotton rats.





















Figure 5 -- Lower teeth of some fossil and Recent cricetid

rodents. A = Sigmodon bakeri, holotype UF 11700,

Coleman IIA, B = Sigmodon hispidus, UF 549, Re-

cent specimen from Brevard Co., Fla., C = Pitymys

pinetorum, UF 14387, Reddick IA: small numbers

correspond to triangles, D = Pitymys pinetorum

nemoralis, UK 54262, Recent specimen from Green-

wood Co., Kansas, E = Pitymys ochrogaster haydeni,

UK 20772, Recent specimen from Scott's Bluff,

Nebraska, F = P. o. haydeni, UK 20760, Scott's

Bluff, Neb., G = Pitymys pinetorum, UF 4860,

Haile XIB. The arrows point out the salient fea-

ture that separates Pitymys pinetorum from P.

ochrogaster (see discussion under Pitymys arata).









left right f;
9
61 7 6

5 4
53 2
F2 F S ^'1 f












(3
j:D











Discussion: Discovery of other fossil Sigmodon species in Florida, from

the Blancan Haile XV deposit in Alachua County and the Inglis IA site

in Levy County, prompted a study of other North American fossil samples

of this genus. An annotated list of the living and extinct species and

extinct subspecies is presented below. Some of these taxa are new, and

are described in the species account which follows the list. A cross in

front of a taxon indicates that it is extinct.

hispidus species group

hispidus

alleni

ochrognathus

fulviventer

+bakeri new species

leucotis species group

leucotis

perunanus

+curtisi

+hudspethensis

alstoni species group

alstoni

+ medius species group

+medius

+medius medius new subspecies

+medius hibbardi new subspecies

+minor











Specimens referred to new taxa, except for those of S. baker, as well

as those of all other fossil Sigmodon taxa studied, are listed under

"Fossil Material Examined" at the end of the section of this report

dealing with Sigmodon.



Key to the Extinct and Extant Species of Sigmodon


l.a. First lower molar with four well developed roots ................2

b. First lower molar with three well developed roots................ 7

2.a. Relatively low crowned molars; reentrant folds broad and shal-

low; lingual root reduced .......................+S. hudspethensis

b. Hypsodont molars; reentrant folds characteristically narrow

and deep; lingual root well developed............................3

3.a. Mental foramen located at anterior base of ML and lingually

directed (not visible from labial view) ..................S. alleni

b. Mental foramen anterior to the base of MI and partly labially

directed (visible from labial view)..............................4

4.a. Anterior cingulum on M2-tMusually well developed; anteroconid

of MI anteriorly-posteriorly flattened in specimens with

little tooth wear ............................................... 5

b. Anterior cingulum on M2-M3 moderately developed to absent;

anteroconid of M1 not anteriorly-posteriorly flattened in

specimens with little tooth wear ...............................6

5.a. Size small; lower third molar relatively short.....S. ochrognathus

b. Size large; lower third molar relatively long.......S. fulviventer










6.a. Anterior cingulum on M2-M3 grading from moderately developed

to absent, characteristically present; M1 usually without

posteriorly extended anteroconid; size large............S.hispidus

b. Anterior cingulum on M2-M3 characteristically absent; M1

with posteriorly extended anteroconid; size small .......+S. baker

7.a. Upper incisors grooved..................................S. alstoni

b. Upper incisors, when known, not grooved..........................8

8.a. Anterior cingulum on M2-M3 absent.....................S. peruanus

b. Anterior cingulum on M2-M3 usually well developed............... 9

9.a. Size and dental pattern approximating that of

S. hispidus..................................+S. curtisi and S. leucotis*

b. Size small; dental pattern not as in S. hispidus................10

10.a. Size relatively large; reentrant folds relatively

broad ................................................... +S. medius

b. Size relatively small; reentrant folds relatively

narrow....................................................+S. minor



I cannot separate the dentitions of these two species,

though perhaps the anterior cingulum on M2-M3 is a bit

less developed in S. leucotis. As noted in the Species

Account, the interparietal bone is absent or at most

vestigial in S. leucotis, but as no skull material of

S. curtisi has been discovered I retain the integrity

of this species.






-42-


Account of the Extinct and Extant Species of Sigmodon


Genus Sigmodon Say and Ord 1825

Characteristics of the genus are adequately delimited by Hershkovitz

(1955). Taxonomy of the Recent North American species follows Baker

(pers. commun.), although the species groups are in part my develop-

ment. Much work needs to be done with living South American Sigmodon,

and for now I have merely lumped all beasts in that continent with three

roots on the MI into either Sigmodon peruanus or S. alstoni, depending

upon the condition evidenced by the upper incisors.


hispidus species group

Diagnosis: This group is characterized by possessing four well de-

veloped roots on the first lower molar. All species except S. bakeri

are extant and distributed almost entirely in North America.

Geologic Range: Latest Irvingtonian to Recent.


Sigmodon hispidus Say and Ord 1825

Diagnosis: The largest North American cotton rat (Table 6), Sigmodon

hispidus is the most advanced cotton rat with respect to dental evolu-

tion. The process of lamination as described by Hershkovitz (1962)

has proceeded in this species to the point of separation of the ante-

roconid from the paraconid and entoconid in some specimens. The cheek

teeth are highly prismatic and the reentrant folds are deep and nar-

row. The enamel surface at the termination of each reentrant fold is

thinned relative to the enamel occlusal surface along the remainder of

the border of each fold. The anterior cingulum on the M2 and M3 tends

to be reduced.











Geologic Range: Rancholabrean to Recent

Florida:

Devil's Den: Martin, 1968a; Wisconsin
Haile VIIIA: unpubl.; Sangamon
Haile, Locs. XIB, XIIIA, C: unpubl.; ?Sangamon
Withlacoochee River 7A: unpubl.; Wisconsin
Ichetucknee River; unpubl.; Wisconsin
Vero: Weigel, 1962; Wisconsin
Seminole Field: Simpson, 1929; Wisconsin
Melbourne: Ray, 1958; Wisconsin
Reddick IIC: unpubl.; Sangamon
Reddick IA: Gut and Ray, 1963; Sangamon
Sabertooth Cave: Simpson, 1928; Sangamon
Kendrick I: unpubl.; Sangamon
Maximo Moorings: unpubl.; Wisconsin
Arredondo IA: unpubl.; Wisconsin
Arredondo IIB: unpubl.; Sangamon
Arredondo IIC: unpubl.; Sangamon

Louisiana:

Little Bayou Sara: Martin, 1968a; Wisconsin

Georgia:

Ladds: Ray, 1967; Sangamon?

Texas:

Moore Pit: Slaughter, 1966; Sangamon?
Sims Bayou: Slaughter and McClure, 1965; Wisconsin?
Howard Ranch: Dalquest, 1965; Wisconsin
Clear Creek: Slaughter and Ritchei, 1963; Wisconsin
Friesenhahn Cave: Lundelius, 1960; Wisconsin
Longhorn Cavern: Semken, 1961; Wisconsin
Ben Franklin: Slaughter and Hoover, 1963; Wisconsin

New Mexico:

Brown Sand Wedge: Slaughter, 1962; Wisconsin

Aruba:


Isla: Hooijer, 1967; Wisconsin?










Sigmodon alleni Bailey 1902

Diagnosis: Sigmodon alleni is best characterized by position of the

mental foramen of the mandible. This foramen cannot be seen when the

mandible is viewed from the labial side, as it is located close to the

base of the first lower molar and more lingually directed than in other

Sigmodon species. The dental pattern is most similar to that of Sigmodon

hispidus.

Geologic Range: No fossil record.


Sigmodon ochrognathus Bailey 1902

Diagnosis: Sigmodon ochrognathus is the smallest of the living Sigmodon

species (Table 6), and like S. fulviventer, demonstrates a peculiar

anteriorly-posteriorly compressed anteroconid on the M1 in specimens

with little tooth wear.

Geologic Range: No fossil record.


Sigmodon fulviventer Allen 1889

Diagnosis: This diagnosis applies to S. f. minimus, the only sub-

species I have viewed. In size S. fulviventer approaches S. hispidus

(Table 6), and with the exception only of the anteriorly-posteriorly

compressed anteroconid of the Ml, the dental pattern approximates that

of S. hispidus.

Geologic Range: No fossil record.


+ Sigmodon baker Martin 1969

Diagnosis: As discussed previously. Sigmodon bakeri represents the

earliest record in North America of the hispidus species group, but the

specialized condition of absence of the anterior cingulum on the M2-M3






-45-


disallows it as an ancestor for any other hispidus group species. The

dental pattern, with the exception of the character mentioned above, is

somewhat intermediate between the primitive 3-rooted Ml species and the

hispidus species group in that the enamel borders of the reentrant folds

are not as thinned as they are in the other hispidus group species. The

reentrant folds also tend to be wider.

Geologic Range: Latest Irvingtonian through early Rancholabrean of

Florida:

Coleman IIA: this report; late Illinoian?
Haile VIIA: this report; Sangamon
Williston III: this report; Sangamon
Bradenton 51st St.: this report; Sangamon


leucotis species group

Diagnosis: Characteristically with three, occasionally with four,

roots on the first lower molar.


Sigmodon leucotis Bailey 1902

Diagnosis: The dental pattern of S. leucotis is essentially the same as

that of S. hispidus. Examination of 11 specimens demonstrated 7 with

three roots on the M1 (lingual root missing) and 4 with four roots on

the MI; of the latter 4, the lingual root was developed as well as in

S. hispidus in 2, and as a small peg in the other 2.

Geologic Range: No fossil record.


Sigmodon peruanus Allen 1897

Diagnosis: Sigmodon peruanus is the largest living Sigmodon species

(Table 6). It is further characterized through loss of the anterior

cingulum on the M2-M3 and by the highly prismatic, flatly worn enamel










reentrant fold borders. Of 10 specimens examined, 9 evidenced only three

roots on the Ml, and one specimen, USNM 303005 from Tumbes, Peru,

possessed four well developed roots on this tooth.

Geologic Range: No fossil record.


+Sigmodon curtisi Gidley 1922

= Sigmodon cf S.his~is Hibbard, 1952;
Vertebrata, Art. 2: 1-14.

Diagnosis: Sigmodon curtisi is a large cotton rat (Table 6) which demon-

strates a dental pattern as in S. hispidus and S. leucotis. In fact, I

am unable to separate the fossil material of S. curtisi from Recent speci-

mens of S. leucotis. The interparietal bone is absent or vestigial in

S. leucotis, and is well developed in all other Sigmodon species, but as

no skull material of S. curtisi has yet been recovered I retain the in-

tegrity of both species. Two out of six first lower molars of S. curtisi

from the Inglis IA deposit of north Florida evidence 4 roots on the MI,

placed as in the hispidus species group. Non-Florida curtisi that I have

examined apparently evidence only 3 roots on the Ml, but the preserva-

tion of this material is not very good and the teeth are imbedded in the

mandibles, which makes examination quite difficult.

Geologic Range: Irvingtonian:

Arizona: Curtis Ranch; Gidley, 1922

Kansas: Kentuck Assemblage; Hibbard, 1952

California: Vallecito Creek; unpubl.

Florida: Inglis IA; unpubl.






-47-


+Sigmodon hudspethensis Strain 1966

Diagnosis: Unfortunately the holotype, a lower right first molar, UT

40857-10, was lost before it could be properly studied. It had been

measured, however, and these data are included in Table 6. It, there-

fore, seems prudent to designate a neotype. The paratype, another lower

right MI, is available, but a more recently collected specimen, found

after Strain's (1966) paper was published, makes a better neotype. The

new specimen, collected by William Akersten, is described below.


Neotype: UT 40857-10, a left mandible with all cheek teeth. Both

anterior and posterior portions of the ramus are broken off, but the in-

cisor is present. Collected by William Akersten from the Hudspeth

Fauna (Red Light Local Fauna), Love Formation, Hudspeth County, Texas;

late Blancan?

Amended Diagnosis: Contrary to Strain (1966), the dental pattern of

S. hudspethensis does not vary significantly from that of S. medius.

It does, however, differ from the medius species group in possessing a

well developed labial root on the first lower molar, obvious in the

neotype. The first lower molar of S. hudspethensis also has a fourth

peg-like lingual root, developed as in the two speciments of S. leucotis

mentioned previously that also evidenced peg-like fourth lingual roots.

This lingual root is not as well developed as it is in the hispidus

species group.

Strain (1966) hinted at the fact that Sigmodon hudspethensis was

larger than either S. medius or S. minor, but provided no comparative

measurements. These data are presented in Table 6, and support Strain's

suggestion that S. hudspethensis was "A cotton rat about the size of











Sigmodon hispidus . "

Geologic Range: Late Blancan? of Texas:

Hudspeth Fauna: Strain, 1966; Akersten, 1968.


alstoni species group


Sigmodon alstoni Thomas 1880

Diagnosis: Sigmodon alstoni is relegated to its own species group by

virtue of the fact that it is the only Sigmodon species to have developed

grooved upper incisors. The primitive nature of this species is evi-

denced by the fact that it possesses only three roots (lingual root

absent) on the first lower molar.

Geologic Range: No fossil record.


+medius species group

Diagnosis: The members of this group, S. medius and S. minor, are the

the most primitive of known Sigmodon species. They are small cotton

rats (Table 6) with little to no development of labial and lingual

roots on the first lower molar. The incisor capsular process of the

mandible is least developed in these species; a primitive trait for

cricetid rodents in general.


+Sigmodon medius Gidley 1922

= Sigmodon intermedius; Hibbard, 1938,
Trans. Kansas Acad. Sci. 40: 239-265.

Diagnosis: Sigmodon medius is characterized by having only 2 or 3

roots on the first lower molar. The labial root is always more greatly

developed than is the lingual root, but both are usually tiny pegs and










may be centrally, rather than lingually and labially, located. The lin-

gual root is about as well developed as is that root in the neotype of S.

hudspethensis, but it is much less developed than is the lingual root in

the hispidus species group. In two out of fifty-four specimens viewed,

solely from the Rexroad Local Fauna, Locality No. 3 (Figure 7), there were

four roots on the first lower molar, but the two accessory roots were

centrally located and very minute.

There are no morphological differences between Sigmodon medius

Gidley and S. intermedius Hibbard, and Figure 8 and Table 6 demonstrate

that they are also equal in size.

Compared to all hispidus group species and S. leucotis and S.

curtisi of the leucotis species group, the dental pattern of S. medius

is much less prismatic. The reentrant folds are not particularly deep

as they are in the other species, nor are they as narrow. In the species

mentioned above the enamel borders of the reentrant folds are greatly

thinned at the termination (apex) of each fold; a development I believe

which is correlated with structural relationships allowing the posterior

enamel border of a particular reentrant fold to double back (Figure 5)

closely adhered to the anterior enamel border of the same fold. An-

other way of describing this pehnomenon in the hispidus species group

and in S. leucotis and S. curtisi is, for example, that the posterior

enamel border of the protoconid is closely allied with the anterior

enamel border of the hypoconid (dental terminology after Hooper, 1957).

The anteroconid of the M1 in S. medius is generally small and

usually symmetrical, with a wide fourth reentrant fold.






-50-


+Sigmodon medius medius, new subspecies

Holotype: USNM 10519, the holotype of Sigmodon medius described by

Gidley (1922).

Diagnosis: Species characteristics as described for S. medius. This

subspecies differs from S. m. hibbardi by virtue only of smaller size

(Figure 8, Tables 6 and 8). The distinction between the subspecies is

further discussed under S. m. hibbardi.

Geologic Range: Early Blancan through latest Blancan:

Kansas:

Rexroad Local Fauna, Loc. No. 3; Hibbard, 1938
Sanders Local Fauna; unpubl.

Arizona:

Benson Ranch Local Fauna: Gidley, 1922
Tusker Local Fauna: unpubl.

California:

Arroyo Seco Fauna: unpubl.
Layer Cake Fauna: unpubl.


+Sigmodon medius hibbardi, new subspecies

Holotype: UMMVP 35093, a right mandible with all cheek teeth, from the

Wendell Fox Pasture locality, Meade County, Kansas; Blancan.

Etymology: This subspecies is named in honor of Dr. Claude Hibbard of

the University of Michigan for his manifold contributions to the field

of vertebrate paleontology, and especially for providing a Pleistocene

stratigraphic sequence in Kansas, complete with fossil mammals, which is

unparalleled in any area of the New World.

Diagnosis: The Wendell Fox Pasture sample of S. m. hibbardi is plotted

in Figure 8, and the log difference plot for this subspecies is seen to










be different from that of S. m. medius. The mean values of four of the

seven measurements taken (Table 8, Figure 8) in S. m. hibbardi are

statistically significantly different from those taken in S. m. medius

at the 90% level of probability (p < .1). The dental pattern is other-

wise identical to that of S. m. medius.

Geologic Range: Early or late Blancan:

Kansas:

Wendell Fox Pasture Locality: unpubl.

California:

Transition zone between the Arroyo Seco Fauna
and the Vallecito Creek Fauna: unpubl.


+Sigmodon medius, subsp. indeterminate

Sigmodon medius has been recovered from the following localities,

but the small samples preclude statistical treatment. Measurements of

the samples are presented in Table 6.

Kansas:

Benders Local Fauna: unpubl., early Blancan

Texas:

Blanco Local Fauna: unpubl., Blancan

Florida:

Haile XVA Local Fauna: unpubl., late Blancan?

Nebraska:


Sand Draw Local Fauna: unpubl., Blancan.







-52-


+Sigmodon minor Gidley 1922

= Sigmodon hill; Hibbard, 1941. State Geol.
Surv. Kansas, Bull. 38: 197-220.

Diagnosis: Sigmodon minor is the smallest known species of Sigmodon

(Table 6), and appears to have been derived directly from Sigmodon

medius. As seen in Figure 8 there are no dental proportional differ-

ences between S. minor and S. medius. The major difference between

S. minor and S. medius is size. The reentrant folds are deeper and

narrower in S. minor than they are in S. medius, especially obvious in

teeth with little wear, but well worn teeth of S. minor approximate

very closely those of S. medius.

There are no qualitative differences between Sigmodon minor Gidley

and S. hill Hibbard, and Figure 8 and Table 6 demonstrate that these

species are equal in size as well.

The Borchers Sigmodon minor include five first lower molars with

4 roots; out of 27 specimens studied. A random selection of 27 S.

medius included two with 4 roots. This difference is not statistically

significant y2with Yates Continuity Correction= .657; one degree of

freedom).

Geologic Range: Irvingtonian:

Kansas:

Borchers Local Fauna: Hibbard, 1941

Arizona:

Curtis Ranch Local Fauna: Gidley, 1922.


Evolution in the Genus Sigmodon

Living sigmodont rodents include the genera Reithrodon, Neotomys,












Sigmodon, and Holochilus (Hershkovitz, 1955). All but Sigmodon are re-

stricted to South America. The genus Sigmodon exists now in northern

South America and extends northward through Central America into the

southern United States. All sigmodonts possess a complex penis and a

long-wide palate. According to Hershkovitz (1955), "Diagnostic charac-

ters of sigmodonts include reduced outer hind toes, webbed middle hind

toes, spinous process of zygomatic palate, specialized posterior palatal

region, simplified molars characterized by absence or obsolescence of a
1-2
functional mesoloph(id) in, at least, Mi:, and the S-shaped enamel pat-

tern of M3." Hershkovitz (1955) further suggests that Sigmodon is the

most generalized form of the living sigmodonts.

"Evolution of American cricetines has paralleled that of the New

World Perissodactyla. The primitive brachydont, buno-mesolophodont

cricetines have survived, like the tapir, in forested parts of the

range. Like the horse, the progressive branch of cricetines, with

mesoloph absent or vestigial, has become increasingly specialized for

life in open country and a diet of grasses. The young have lost, or are

in the process of losing, the distinctive juvenal phase of pelage compar-

able to the spotted coat of young tapirs and other woodland ungulates.

The molars have become higher, their crown surfaces flatter and tending

toward lamination. The third molar of grazing cricetines is nearly

always precociously functional. This condition provides the needed

maximum grinding surface which, in young ungulates, is supplied by

deciduous premolars.

Sigmodont rodents are members of the relatively recently evolved,

essentially grazing, New World mammalian fauna of open country. Morpho-

logically, they merge into the phyllotine group (Phyllotis, Hesperomys,







-54-


and others) by a combination of characters. In both groups the denti-

tion is fundamentally similar (Hershkovitz, 1955)." Hershkovitz (1962)

further states, "Phyllotines probably evolved from the same line that

gave rise to akodont rodents. The sigmodonts . are more special-

ized but appear to be progressive offshoots from the main phyllotine

line."


I. Dental Evolution from Pliocene to Recent Time

The following information is now available:

1) The most generalized South American phyllotine rodents,

from which Sigmodon was supposedly derived, possess 4

roots on the first lower molar (Hershkovitz, 1962).

2) The earliest fossil Sigmodon species known is S. medius.

This species is found in late Pliocene deposits, has

the most primitive dental pattern of all recognized

Sigmodon species (see the discussion under S. medius

in the Species Account), and characteristically evi-

dences 2 or 3, rarely 4, roots on the first lower

molar. The lingual and labial roots (accessory roots)

are typically minute and most often located more to-

wards the center of the tooth than they are in the hispi-

dus species group.

3) Sigmodon hudspethensis, a larger animal than S. medius,

approximating the size of S. curtisi and S. hispidus,

is the only Sigmodon species other than S. medius known

from early Pleistocene (late Blancan) deposits. This

species may possess 4 roots on the first lower molar,










the accessory roots developed more fully than they are

in S. medius, but less fully than in the hispidus species

group.

4) Sigmodon curtisi, with a dental pattern as in the his-

pidus species group and as in S. leucotis, first appears

during the early Irvingtonian (early middle Pleistocene)

in North America, and may have 4 well developed roots

on the first lower molar.

5) Three living species of Sigmodon in the New World char-

acteristically evidence 3 roots on the first lower molar,

and all may evidence 4 well developed roots occasionally.

One of these species, S. leucotis, is restricted to iso-

lated populations at higher elevations in Mexico (Baker,

pers. commun.) surrounded by hispidus group species.

Teeth of S. leucotis are similar to those of S. curtisi.

The remaining two species, S. alstoni and S. peranus,

are restricted to South America, and appear to have

evolved in isolation from their North American relatives.

6) The hispidus species group (M1 with 4 well developed

roots and complex molars) is first seen in North America

during the latest middle Pleistocene (latest Irvington-

ian).


The fossil record for cotton rats is one of the most complete of

any genus of small mammal that existed and evolved in the New World

through Pleistocene epoch. A perfectly adequate evolutionary scheme











can be developed for the genus based solely on the fossil material

available from deposits in the United States. However, this scheme will

undoubtedly be distasteful to many people, as it requires an evolution-

ary reversal in root count. An alternative model may also be developed,

but it requires hypothesizing extinct creatures which are not repre-

sented by fossil material.

If Hershkovitz (1955, 1966) is correct, the first Sigmodon species

evolved from a generalized phyllotine rodent in South America and then

dispersed northward. The living phyllotine forms which according to

Hershkovitz (1962) most closely approximate a generalized beast, such

as Phyllotis darwini, Galenomys garleppi, and Calomys spp., possess 4

roots on the first lower molar. As demonstrated by the information

summarized on page 54 there is an increase in numbers of roots on the

first lower molar and increased dental complexity in fossil Sigmodon

from the late Pliocene S. medius (2 or 3 roots) to the late Pleistocene

hispidus species group (4 roots). Therefore, if the evolutionary trend

disclosed by the available fossil material is valid, an evolutionary

reserval in root count is indicated (4-3-2-3-4). This system is outlined

in Figure 6.

The alternative model would require that: 1) S. medius does not

give rise to S. hudspethensis, 2) S. curtisi is not ancestral to the

hispidus species group, and 3) evolution to the curtisi stage in

North America is paralleled in Central or South America by another

line leading to a curtisi-like animal in which, however, all grades

retain 4 well developed roots on the first lower molar. The resultant

end product of this line then evolves into the hispidus species

group.


I













































SU N
o *.l *

*0 0- Z
S.0
ca 3
au a)
0 co
0 z
N *-,4 (

-t a, N





cu 0
CO p


i CI N


o 0 44 N

Br 13

p 4-4 Q )







0p


'-4
ak
*r-
1^M















U


PLE/STOCENE


I- I


C,
C,


- I -


Late Blancan


Irvingtonian


Zi c> o I
W" .z a tT cS =

lb,

III



C, ~



lb



5t z





__ II ___ _
-c -5- -


PLIOCENE





















Figure 8 -- Composite ratio diagram of measurements of the

lower dentition and mandible in some members

of the Sigmodon medius species group from

Kansas and Arizona. A = Sigmodon medius

medius; Benson Ranch, B Sigmodon medius

medius; Tusker, C = Sigmodon minor; Curtis

Ranch, D Sigmodon medius hibbardi; Wendell

Fox Pasture, E = Sigmodon medius medius; Rex-

road Loc. 3, F = Sigmodon medius medius;

Sanders, G = Sigmodon minor; Borchers.

MA = mandibular alveolar length, 1 = length,

w = width. The standard is the Coleman IIA


Sigmodon baker.






















V -I 3


HE1


vi3w


I11











II. Ecological Considerations

Early and middle Pliocene deposits in the United States contain

cricetine species referrable to Copemys, Peromyscus, Tregomys, or

Gnomomys. Sigmodon has not been recorded from deposits of the above

ages, and yet is the most abundant cricetine in deposits of early and

late Blancan age in the United States. One might call the appearance

of Sigmodon in these deposits "sudden." Sigmodon entrance into the United

States also corresponds in general to the influx of rooted-cheek-toothed

microtines such as Pliopotamys, Ophiomys, Pliophenacomys, Pliolemmus,

and Ogmodontomys. The beginning of this microtine immigration is re-

corded, for example, in the late Hemphillian McKay Reservoir Local

Fauna of Oregon (Shotwell, 1956), a fauna which contains Teleoceras and

the extinct microtine Prosomys mimus. Teleoceras is unknown in early

Blancan faunas such as Rexroad, and is generally believed to have be-

come extinct by the end of the Hemphillian (Hirschfeld and Webb, 1968).

It is interesting to speculate how, in the earlier Pleistocene,

the vole-like Sigmodon could be sympatric with such an array of rooted-

cheek-toothed microtines, and the answer, I believe, is readily appar-

ent. The dental evolutionary trends which characterize Sigmodon in

general, and especially the medius-minor line, are those which point to

convergence with the true (rootless-cheek-toothed) voles; notably hypsodonty

and involution. Disappearance of the medius species group coincides ap-

proximately with the appearance of the rootless-cheek-toothed microtines

(Pitymys, Pedomys, Neodon) which first appear in the Cudahy Fauna of

Kansas, of Kansan age (Paulson, 1961; Hibbard, 1967).

These considerations suggest that the earliest Sigmodon species

were not in direct competition with the early, rooted-cheek-toothed











microtines, and were filling the grassland niche later to be filled

more adequately by the rootless-cheek-toothed microtines. I further sug-

gest that most of the early rooted-cheek-toothed microtines were sylvan

and aquatic rather than pastoral, as is the case in the living North

American rooted-cheek-toothed forms Clethrionomys, Phenacomys, and

Ondatra. This hypothesis is partly substantiated by Hibbard's and

Zalazewski's statement (1967) that Pliopotamys was ancestral to the

aquatic Ondatra.

Sigmodon is found today primarily in the Lower Austral and Tropical

life zones in North America. Microtines are generally Holarctic mammals,

and only Microtus mexicanus, Pitymys pinetorum, P. quasiater, and tiny

populations of three species, Pitymys guatemalensis, Microtus umbrosus,

Pitymys oaxacensis are able to exist in life zones lower and warmer than

the Upper Austral zone. Both P. pinetorum and P. quasiater are sylvan

fossorial species, and thus in general Microtus and Pitymys are rare in

grasslands in the southern United States, Mexico, and Central America.

This niche is today filled primarily by Sigmodon, although other genera

such as Reithrodontomys and Oryzomys also contribute an appreciable

amount of biomass.


III. Fossil Material Examined

Sigmodon medius

S. m. hibbardi:

1. Wendell Fox Pasture Locality, Meade County, Kansas:

UMMVP 35093, 57050-57054

2. Transition between Arroyo Seco Fauna and Vallecito

Creek Fauna, 3200 to 3250 feet from top of sequence,











San Diego County, California:

LACM 1588/4442, 1451/4447


S. m. medius:

1. Arroyo Seco Fauna, 4900 to 5350 feet from top of

sequence, San Diego County, California:

LACM 6554/13754, 6552, 6550, 6552/12505

2. Layer Cake Fauna, 6750 feet from top of sequence,

San Diego County, California:

LACM 1711/7005

3. Rexroad Local Fauna, Locality 3, Meade County, Kansas:

UMMVP 29162, 29669, 31085, 31086, 41193,

44589, 56249

4. Sanders Local Fauna, Localities 1, 2, 4, Meade

County, Kansas:

UMMVP 32003-32005, 31997, 31998, 56247,

56248, 50263, 50264

5. Tusker Local Fauna, Locality 15-24, Graham County,

Arizona:

UAVP 899, 905, 910, 913, 914, 922, 924, 925,

927-936, 938-941, 945, 949, 966-970, 972-1003,

1007,1020, 1023-1025, 1030, 1036-1042, 1054,

1056, 1057, 1059-1069, 1075, 1077-1079, 1081,

1087, 1089, 1090, 1094, 1100, 1104, 1105,

1111, 1113, 1114, 1118, 2494-2510, 2513, 2514,

2519, 2700-3053










Sigmodon medius

S. m. medius

6. Benson Ranch Local Fauna, Cochise County, Arizona:

USNM 10520-10523

S. medius, subsp. indeterminate

1. Benders Local Fauna, Meade County, Kansas:

UMMVP 45820

2. Haile XVA Local Fauna, Alachua County, Florida:

UF 12334, 12336, 12338, 12342

3. Sand Draw Local Fauna, Brown County, Nebraska:

UMMVP 57056

4. Blanco Local Fauna, Crosby County, Texas:

MUVP 7146


Sigmodon minor

1. Borchers Local Fauna, Meade County, Kansas:

UMMVP 35766, 56244, 56245, 51302, 51312,

51313, 51307, 51305, 51303, 51309, 51311,

51314, 51308, 51306, 51304,

2. Curtis Ranch Local Fauna, Cochise County, Arizona:

USNM 10512-10518, 16608-16611


Sigmodon hudspethensis

1. Hudspeth Fauna, Madden Arroyo, Hudspeth County,

Texas:


UTMM 40240-1, 40240-2






-67-


2. Hudspeth Fauna;

Red Light Local Fauna, Hudspeth County, Texas:

UTMM 40857-10, 40857-11


Sigmodon curtisi

1. Curtis Ranch Local Fauna, Cochise County, Arizona:

USNM 10511, 16606, 16607, 16605

2. Kentuck Assemblage, McPherson County, Kansas:

UKMVP 7361

3. Vallecito Creek Fauna, 900 to 1520 feet from top

of sequence, San Diego County, California:

LACM 1615/4389, 1114/3394, 1297/6941, 1114/3395,

1461/4445, 1615/4396, 1615/4398

4. Inglis IA Local Fauna, Citrus County, Florida:

UF 15155


Sigmodon hispidus

1. Reddick IA, rodent beds, Marion County, Florida:

UF 14347-14360

2. Reddick IIC, Marion County, Florida:

UF 15204

3. Devil's Den, Levy County, Florida:

UF 13440, 13453, 13444, 13593-13600

4. Kendrick I, Marion County, Florida:

UF 2658

5. Maximo Moorings, Pinellas County, Florida:

UF 3062










6. Haile VIIIA, Alachua County, Florida:

UF 9844, 15153, 12680-12684

7. Haile XIB, Alachua County, Florida:

UF 13471-13592

8. Haile XIIIA, Alachua County, Florida:

UF 13096-13097

9. Haile XIIIC, Alachua County, Florida:

UF 13049

10. Ichetucknee River, Gilchrist County, Florida:

UF 15205

11. Withlacoochee River, Locality 7A, Citrus County,

Florida:

UF 15206

12. Arredondo IA, Alachua County, Florida:

UF 15207

13. Arredondo IIB, Alachua County, Florida:

UF 12589

14. Arredondo IIC, Alachua County, Florida:

UF 12297-12303















Table 6

Measurements (in mm) of the lower dentition
and mandible in living and extinct species of Sigmodon

MA = mandibular alveolar length, 1 = length, w = width



MA

N X O.R.

Sigmodon medius

Benson Ranch 3 5.75 5.59-6.01
Tusker 25 5.70 5.30-6.13
Rexroad, Loc. 3 8 6.17 5.97-6.42
Sanders 5 6.07 5.76-6.44
Benders -
Sand Draw -
Blanco 1 5.58
Haile XV -
Wendell Fox Pasture 3 6.27 6.18-6.38

Sigmodon minor

Curtis Ranch 8 5.30 4.97-5.80
Borchers 25 5.63 5.27-6.00

Sigmodon curtisi

Curtis Ranch 1 7.03
Inglis IA 4 6.68 6.27-6.91
Kentuck 1 6.78

Sigmodon hudspethensis

Hudspeth and Red Light 1 6.90

Sigmodon bakeri

Coleman IIA 11 6.28 5.93-6.71
Williston III 2 6.69 6.40-6.98













Table 6 continued


MA (continued)


N X 0.R.


Sigmodon hispidus

Reddick IA
Florida (Recent)
Texas (S. h. berlandieri)

Sigmodon ochrognathus


Texas


Sigmodon fulviventer


Mexico; Durango


Sigmodon alleni

Mexico; Michoacan and Oaxaca

Sigmodon leucotis

Mexico; Durango, Morelos,
Guererro, Guanajuato


Sigmodon peruanus

Ecuador and Peru


7.27 6.83-7.65
7.26 6.56-7.80
6.68 6.34-6.93


4 6.12 5.81-6.29



8 7.17 6.95-7.34



5 6.64 6.38-7.08


11 6.76 6.44-7.05



10 7.72 7.17-8.23


Sigmodon medius

Benson Ranch
Tusker
Rexroad, Loc. 3
Sanders
Benders
Sand Draw
Blanco
Haile XV
Wendell Fox Pasture


1.91-2.29
1.86-2.26
1.80-2.26
1.94-2.14


1.98-2.00
2.18-2.58
2.10-2.22













Table 6 continued


LM1 (continued)


Sigmodon minor

Curtis Ranch
Borchers

Sigmodon curtisi

Curtis Ranch
Inglis IA
Kentuck

Sigmodon hudspethensis

Hudspeth and Red Light

Sigmodon bakeri

Coleman IIA
Williston III

Sigmodon hispidus

Reddick IA
Florida (Recent)
Texas (S. h. berlandieri)

Sigmodon ochrognathus

Texas

Sigmodon fulviventer

Mexico; Durango

Sigmodon alleni

Mexico; Michoacan and Oaxaca

Sigmodon Leucotis

Mexico; Durango, Morelos,
Guererro, Guanajuato

Sigmodon peruanus

Ecuador and Peru


N i 0.R.



9 1.92 1.73-2.19
38 1.88 1.72-2.07



3 2.41 2.28-2.49
5 2.35 2.22-2.50
1 2.42



4 2.34 2.19-2.58



20 2.21 2.04-2.46
3 2.46 2.28-2.61



18 2.49 2.24-2.72
30 2.47 2.11-2.73
8 2.35 2.18-2.49



4 2.15 2.10-2.20



8 2.27 2.20-2.39



5 2.41 2.27-2.57


2.54



2.68


2.44-2.75



2.31-3.03













Table 6 continued

LM2
N X O.R.


Sigmodon medius

Benson Ranch
Tusker
Rexroad, Loc. 3
Sanders
Benders
Sand Draw
Blanco
Haile XV
Wendell Fox Pasture

Sigmodon minor

Curtis Ranch
Borchers

Sigmodon curtisi

Curtis Ranch
Inglis IA
Kentuck

Sigmodon hudspethensis

Hudspeth and Red Light


Sigmodon bakeri


Coleman IIA
Williston III


1.51
1.52
1.56
1.54
1.67
1.53
1.41
1.49
1.60


1.43-1.57
1.35-1.71
1.33-1.81
1.40-1.69




1.53-1.65


9 1.42 1.30-1.62
40 1.38 1.22-1.54


1.85-1.89
1.75-1.85


2 1.75 1.73-1.76



13 1.61 1.49-1.75
2 1.76 1.66-1.85


Sigmodon hispidus

Reddick IA
Florida (Recent)
Texas (S. h. berlandieri)

Sigmodon ochrognathus


Texas


Sigmodon fulviventer


Mexico; Durango


1.82 1.67-1.95
1.77 1.59-1.96
1.72 1.57-1.79


4 1.68 1.50-1.82



8 1.82 1.73-1.91













Table 6 continued


LM2 (continued)


Sigmodon alleni

Mexico; Michoacan and Oaxaca

Sigmodon leucotis

Mexico; Durango, Morelos,
Guererro, Guanajuato


Sigmodon peruanus

Ecuador and Peru


Sigmodon medius

Benson Ranch
Tusker
Rexroad, Loc. 3
Sanders
Benders
Sand Draw
Blanco
Haile XV
Wendell Fox Pasture

Sigmodon minor

Curtis Ranch
Borchers


N X O.R.



5 1.76 1.65-1.87


9 1.78 1.63-1.85



9 2.13 1.83-2.29


1.94
1.97
1.93
1.95
2.15

2.02
1.93
2.02


1.88-2.04
1.61-2.28
1.75-2.14
1.88-2.14


2.01-2.02

1.88-2.16


6 1.84 1.64-2.12
40 1.75 1.40-2.06


Sigmodon curtisi


2.55
2.25 2.14-2.35
2.49


Sigmodon hudspethensis

Hudspeth and Red Light


2 2.21 2.07-2.35


Curtis Ranch
Inglis IA
Kentuck













Table 6 continued


LM3 (continued)


N X O.R.


Sigmodon bakeri

Coleman IIA
Williston III


Sigmodon hispidus

Reddick IA
Florida (Recent)
Texas (S. h. berlandieri)

Sigmodon ochrognathus

Texas

Sigmodon fulviventer

Mexico; Durango

Sigmodon alleni

Mexico; Michoacan and Oaxaca

Sigmodon leucotis

Mexico; Durango, Morelos,
Guererro, Guanajuato


Sigmodon peruanus

Ecuador and Peru





Sigmodon medius

Benson Ranch
Tusker
Rexroad, Loc. 3
Sanders
Benders
Sand Draw


2.59 2.24-3.00
2.56 2.17-2.89
2.40 2.02-2.74


1 1.75



8 2.73 2.59-2.92



5 2.33 2.25-2.40




9 2.20 2.05-2.41



9 2.65 2.25-2.87



WMI


1.43-1.71
1.29-1.51
1.27-1.58
1.21-1.50


13 1.98
1 2.02


1.72-2.37






-75-


Table 6 continued


WMl (continued)
N X O.R.
Sigmodon medius (continued)

Blanco 5 1.39 1.20-1.68
Haile XV 2 1.27 1.25-1.29
Wendell Fox Pasture 6 1.53 1.51-1.57

Sigmodon minor

Curtis Ranch 9 1.31 1.21-1.44
Borchers 39 1.31 1.17-1.48

Sigmodon curtisi

Curtis Ranch 3 1.62 1.55-1.71
Inglis IA 5 1.67 1.51-1.74
Kentuck 1 1.56

Sigmodon hudspethensis

Hudspeth and Red Light 4 1.48 1.40-1.57

Sigmodon bakeri

Coleman IIA 20 1.51 1.35-1.86
Williston III 3 1.61 1.56-1.76

Sigmodon hispidus

Reddick IA 18 1.73 1.63-1.86
Florida (Recent) 30 1.65 1.55-1.88
Texas (S. h. berlandieri) 8 1.63 1.56-1.77

Sigmodon ochrognathus

Texas 4 1.61 1.57-1.64

Sigmodon fulviventer

Mexico; Durango 8 1.71 1.65-1.81

Sigmodon alleni

Mexico: Michoacan and Oaxaca 5 1.63 1.53-1.72

Sigmodon leucotis
Mexico; Durango,Morelos,
Guererro, Guanajuato 9 1.67 1.58-1.75






-76-


Table 6 continued


WM, (continued)
N X O.R.


Sigmodon peruanus

Ecuador and Peru






Sigmodon medius

Benson Ranch
Tusker
Rexroad, Loc. 3
Sanders
Benders
Sand Draw
Blanco
Haile XV
Wendell Fox Pasture


Sigmodon minor

Curtis Ranch
Borchers


9 1.91 1.76-2.07


1.43-1.71
1.39-1.76
1.39-1.68
1.53-1.68




1.62-1.71


9 1.43 1.27-1.55
40 1.42 1.20-1.55


Sigmodon curtisi


1.89 1.85-1.92
1.87 1.73-1.97
1.85


Sigmodon hudspethensis

Hudspeth and Red Light


Sigmodon bakeri

Coleman IIA
Williston III


Sigmodon hispidus

Reddick IA
Florida (Recent)
Texas (S. h. berlandieri)


2 1.52 1.39-1.65



13 1.72 1.55-1.86
2 1.91 1.74-2.08



18 2.02 1.88-2.14
30 1.97 1.79-2.13


Curtis Ranch
Inglis IA
Kentuck














Table 6 continued



WM2 (continued)

Sigmodon ochrognathus


Texas


1.81 1.77-1.84


Sigmodon fulviventer

Mexico; Durango


Sigmodon alleni

Mexico; Michoacan and Oaxaca

Sigmodon leucotis


Mexico; Durango, Morelos,
Guererro, Guanajuato


8 1.93 1.86-2.05



5 1.87 1.71-2.00


1.90 1.81-2.06


Sigmodon peruanus

Ecuador and Peru





Sigmodon medius

Benson Ranch
Tusker
Rexroad, Loc. 3
Sanders
Benders
Sand Draw
Blanco
Haile XV
Wendell Fox Pasture

Sigmodon minor

Curtis Ranch
Borchers


9 2.23 2.10-2.33


1.33-1.62
1.31-1.64
1.34-1.64
1.44-1.64


1.45-1.52

1.52-1.65


6 1.35 1.30-1.40
40 1.36 1.20-1.50


N X


O.R.













Table 6 continued


WM3 (continued)
N X O.R.
Sigmodon curtisi

Curtis Ranch 1 1.81
Inglis IA 2 1.79 1.76-1.82
Kentuck 1 1.83

Sigmodon hudspethensis

Hudspeth and Red Light 2 1.73 1.70-1.76

Sigmodon baker

Coleman IIA 12 1.60 1.43-1.69
Williston III 1 1.61

Sigmodon hispidus

Reddick IA 18 1.88 1.77-1.96
Florida (Recent) 30 1.91 1.77-2.10
Texas (S. h. berlandieri) 8 1.79 1.65-1.89

Sigmodon ochrognathus

Texas 2 1.73 1.70-1.76

Sigmodon fulviventer

Mexico; Durango 8 1.98 1.93-2.09

Sigmodon alleni

Mexico; Michoacan and Oaxaca 5 1.82 1.80-1.88

Sigmodon leucotis

Mexico; Durango, Morelos,
Guererro, Guanajuato 9 1.75 1.66-1.90

Sigmodon peruanus

Ecuador and Peru 9 2.13 2.00-2.35






-79-


Table 7

Measurements (in mm) of the lower dentition and mandible of
Sigmodon samples from the Vallecito Creek-Fish Creek beds

LCF = Layer Cake Fauna; ASF = Arroyo Seco Fauna;
VCF-ASF = transition zone between Arroyo Seco Fauna
and Vallecito Creek Fauna; VCF = Vallecito Creek Fauna;
MA = mandibular alveolar length; 1 = length; w = width


MA L LM2 LM3 WMI WM2 WM3
Sigmodon curtisi


VCF 900 1.84 2.02 -
VCF 1100 7.64 1.94 2.66 1.98 2.29 2.05
VCF 1450 1.85 1.99 -
VCF 1520 7.64 2.79 2.06 2.58 1.85 2.00 1.97
6.99 2.47 2.00 2.82 2.07 2.24 2.04
2.41 1.96 2.47 2.00 2.27 1.83
1.82 1.75 1.86 -
X 7.42 2.56 1.92 2.63 1.93 2.10 1.97

Sigmodon medius hibbardi
VCF-ASF 3200 6.10 2.14 1.73 2.25 1.47 1.70 1.60
1.60 2.08 1.50 1.48
6.20 2.24 1.77 2.04 1.48 1.65 1.63
VCF-ASF 3250 6.53 1.69 2.04 1.73 1.62
X 6.28 2.19 1.70 2.10 1.48 1.65 1.58

Sigmodon medius medius
ASF 4900 5.68 1.54 2.06 1.45 1.50 1.36
ASF 5100 1.70 2.21 1.64 1.59
5.97 1.67 1.96 1.66 1.60 1.51
ASF 5350 5.92 1.59 1.80 1.56 1.39
6.15 2.14 1.62 1.76 1.55 1.49
X 5.93 2.14 1.62 1.96 1.56 1.57 1.47


Sigmodon medius medius
LCF 6750


5.79 2.03

5.79 2.03


1.72
1.51
1.62


1.89
2.02
1.96


1.44

1.44


1.51
1.44
1.48


1.45
1.47
1.46






-80-


Table 8

Statistical comparison of Sigmodon samples from the
Wendell Fox Pasture (WFP) and Rexroad, Loc. 3 (R3)
deposits

N = number of specimens; X = mean; S = variance;
t = student's t value; p = probability value;
= statistically significant difference


.007 8

.002 39

.002 23

.040 15

.001 41

.003 23

.003 15


R3

X

6.17

1.98

1.56

1.93

1.43

1.56

1.48


2
S

.028

.015

.009

.016

.004

.005

.006


.01

*3.09

.90

.90

*10.46

*3.19

*1.89


p

.900

.010

.4> p,.3

.4) p .3

.001

.010

.1> p7.05


MA length

Length M1

Length M2

Length M3

Width M1

Width M2

Width M3


WFP

X

6.27

2.16

1.60

2.02

1.53

1.67

1.59


--






-81-


+Pitymys arata new species

Holotype: UF 11685 (Figure 9) a right dentary with all lower molars.

Both the coronoid process and the angular process are broken, but the

condyloid process is complete. The lower incisor is broken at the

anterior edge of the ramus.

Referred specimens: UF 11684, a partial right dentary with incisor but

no cheek teeth.

Horizon and locality: Coleman IIA Local Fauna, Sumter County, Florida;

late Irvingtonian, ?Illinoian.

Diagnosis: Pitymys arata is a large vole, the size of Microtus richard-

soni (Table 9), and is thus larger than any known Pitymys, extinct or

extant. Configuration of the first lower molar clearly identifies P.

arata as a member of the latter genus. The deep sixth reentrant angle

and posterior sloping anterior enamel border of the fourth triangle sep-

arates P. arata from P. ochrogaster (Figure 5 and Martin, in prep.).

The pattern of the first lower molar combines characteristics of

both P. pinetorum and P. quasiater. The anterior loop, with incipient

sixth and seventh triangles, but with shallow eighth and ninth reentrant

angles, best approximates P. pinetorum. These reentrant angles are

typically deep in P. quasiater. The closed anterior loop in P. arata

(caused by deep penetrance of reentrant angles 6 and 7) is characteris-

tic of P. quasiater. Yet I have seen a few specimens of P. pinetorum

nemoralis (the largest P. pinetorum subspecies) from Kansas with this

feature. The anterior loop on the M1 is widely open in Florida fossil

and extant Pitymys pinetorum. Pitymys arata further differs from P.

pinetorum, but agrees with P. quasiater, in possessing a reduced capsular







-82-


process, especially bulbous in the largest, oldest individuals. The un-

pronounced capsular process of P. arata, related to short length of the

lower incisor, is a primitive trait for all voles.

Etymology: This species is named for Dr. Andrew A. Arata of the World

Health Organization (Geneva) for his guidance early in my graduate

career.

Remarks: The following is a tentative classification of those fossil

and living voles that have cementum in the reentrant angles and rootless

cheek teeth. Emphasis is placed on New World species, and the species

list for neither the Old Worldnor New World is meant to be exhaustive.

Recent species of the New World are listed only if I have transferred

them from the genus in which they were located by Hall and Kelson (1959)

to some other genus. The only Old World species I have transferred to

another genus are those of the taxon Eothenomys, which for my conven-

ience and for reasons which will be explained, appear to be closely

related to those of the genus Anteliomys. Old World species of other

genera are listed below only for illustrative purposes and do not, as in

the case of the New World species, indicate a change in taxonomic status.

This classification is based solely upon the dentition of these animals,

and particularly upon evolution of the M1 as seen in the fossil record

(OW = Old World, NW = New World):

Grade I

Arvicola Lacepede 1799- OW
+A. greenii Hinton
+A. praeceptor Hinton
A. amphibious (Linnaeus)

Phaiomys Blyth 1863- OW, NW











Phaiomys (cont'd)


=+Allophaiomys Kormos 1933, Neue Jahrb. Paleont.
& Miner., Beil-Bd. 69B: 323-346. Munchen.

+P. pliocaenicus Kormos- OW, NW

= +Microtus (Pedomys) llanensis, Hibbard,
1952. Vertebrata, Art. 2: 1-14.

+P. laguroides Kormos- OW
+P. ruffoi- Passa- OW
P. leucurus Blyth OW


Grade II

Neodon Hodgson 1849- OW, NW
+N. paroperarius (Hibbard)- NW
= +Microtus paroperarius Hibbard 1944.
Bull. Geol. Soc. Amer., Vol. 55:
707-754.
N. irene Thomas- OW
N. sikimensis Hodgson- OW
N. carruthersi Thomas- OW


Grade III

Pitymys McMurtie 1831- OW, NW
= Pedomys Baird 1857, in Rept. Expl. Surv., 8(1):
517.
+P. involutus (Cope)- NW
=+Arvicola involuta Cope 1871. Proc. Amer.
Philos. Soc.: 89.
=+Microtus (Pitymys or Pedomys) involutus,
Hibbard, 1955. Proc. Acad. Nat. Sci.
Phila., Vol. CVII: 87-97.
+P. dideltus (Cope)- NW
=+Arvicola didelta Cope 1871. Proc. Amer.
Philos. Soc.; 89.
=+Microtus (Pitymys or Pedomys) dideltus,
Hibbard, 1955. Proc. Acad. Nat. Sci.
Phila., Vol. CVII: 87-97.
+P. hibbardi Holman- NW
+P. arata Martin- NW
+P. meadensis Hibbard- NW
+P. arvaloides Hinton- OW
+P. gregaloides Hinton- OW
P. guatemalensis (Merriam)- NW











Pitymys McMurtie (cont'd)
=Microtus guatemalensis Merriam 1898. Proc.
Biol. Soc. Wash., 12: 108.

P. oaxacensis (Goodwin)- NW
=Microtus oaxacensis Goodwin 1966. Amer.
Museum Novitates, No. 2243: 1-4.
+P. llanensis (Hibbard)
=Microtus (Pedomys) llanensis Hibbard 1944.
Bull. Geol. Soc. Amer., Vol. 55: 707-754.
P. ochrogaster (Wagner)- NW
= Hypudaeus ochrogaster Wagner 1842. in
Schreber, Die Saugthiere ..
suppl., 3: 592.
=Microtus (Pedomys) ochrogaster, Hall and
1959. The Mammals of North America,
Ronald Press, New York, Vol. II.
+P. mcknowni Hibbard 1937. Jour. Mammal.,
18(2): 235.

Microtus Schrank 1798- OW, NW
Alticola Blanford 1881- OW
Neofiber True 1884- NW
Anteliomys Miller 1896- OW
= Eothenomys Miller 1896. North Amer. Fauna,
No. 12: 45.

My studies of fossil and living voles demonstrate three major

grades of dental evolution, each with various side branches. Although

characteristics of the other molars are useful taxonomically, only

the first lower molar appears to be a reliable indicator of evolution-

ary grade. The first grade, including Arvicola and Phaiomys, may be

characterized by the presence of only three closed triangles on the

MI. This grade, first seen in either the upper Pliocene or lower

Pleistocene of the Old World (Hinton, 1926; Kowalski, 1960; Kurten, 1968)

is clearly derivable (probably polyphyletically) from the Old World

rooted-cheek-toothed Mimomys. Arvicola may be separated from Phaiomys

by characteristics of the M3; this tooth in Arvicola retains a well










developed fourth triangle, making the pattern of M3 identical to that of

M2. The fourth triangle of M3 in Phaiomys is reduced or is absent. The

anterior loop of the M1 tends to be simpler in Arvicola, but in reality

there probably is continuing complexity in this feature from Arvicola

through Phaiomys to Neodon.

The genus Neodon (which may eventually be shown to include

Orthriomys, Proedromys, and Blanfordimys) represents the second evolu-

tionary grade, and is intermediate in complexity of the M1 between

grades I and III. The M1 in grade II may have from three to five well

developed triangles, of which only three or four are usually closed.

Triangles four and five are usually confluent and open widely into the

anterior loop, but these triangles are less confluent than in the

genus Pitymys, and the anterior loop is, in Neodon, usually more elongate,

complex, and asymmetrical than it is in Pitymys. Phaiomys ruffoi

(Pasa, 1947) of middle or early Pleistocene sediments from Italy is

possibly the ancestor for living Neodon species and for the extinct

N. paroperarius from the Cudahy fauna in Kansas (Hibbard, 1944: Paul-

son, 1961).

Grade III includes all those voles with an M1 containing at least

five well developed triangles, of which all may be closed. This grade

includes the genera Pitymys (including Pedomys and Herpetomys), Microtus

(including Aulacomys, Chionomys, Stenocranius, Chilotus, and Lasiopodomys),

Alticola, Anteliomys (including Eothenomys), and Neofiber. This grade

is first seen in lower Pleistocene deposits of Europe (Kurten, 1968), but

does not appear in the New World until the early middle Pleistocene

(the Cudahy fauna of Kansas; Paulson, 1961). These early North






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American records include only the genus Pitymys (sympatric with Neodon

paroperarius); Neofiber appears in North America in Port Kennedy Cave

time (Irvingtonian; probably somewhat later than the Cudahy fauna) and

Microtus is not found in North America prior to the Rancholabrean

(Microtus speothen of the Port Kennedy Cave site is either a synonym of

Neodon paroperarius or of the living Microtus oeconomus, the latter

species which is at the Neodon grade of M1 evolution, and perhaps more

properly belongs in the latter genus). The genera Alticola and Anteliomys

are now restricted to the Old World, and I am not aware of any extinct

species allocated to these genera. I have included the genus Eothenomys

within the genus Anteliomys because I do not believe that confluency of

all triangles evolved more than once. The following is a key to the

genera of this grade:

1. Triangles 1 & 2 of MI confluent.............................. Anteliomys

Triangles 1 & 2 of M1 not confluent .............................. 2

2. Triangles 4 & 5 of MI confluent .............................Pitymys

Triangles 4 & 5 of MI not confluent ...............................3

3. Triangle 6 of M1 directed posteriorly; triangle 7 not

usually developed on M1 ..............................Alticola

Triangle 6 of M1 directed mesially; triangle 7 of M1

at least incipiently developed...............................4

4. .Capsular process of mandible undeveloped in adults;

enamel borders of reentrant angles extremely

thick; size large.....................................Neofiber

Capsular process of mandible usually well developed

in adults; enamel borders of reentrant angles

relatively thin; size small ..........................Microtus











The following discussion and species treatment ae limited to the

genus Pitymys.

Pitymys fossils are known from early Pleistocene deposits of

Europe, but are recorded in North America for the first time in the

early middle Pleistocene Cudahy fauna (Paulson, 1961). Pitymys meadensis

may be the ancestor for most later North American species of the same

genus, and based upon published information it is inseparable from the

Old World P. gregaloides of early Pleistocene age (Hinton, 1926, re-

ferred this species to the Upper Pliocene, but the deposits from which

this species is known, the upper freshwater beds at West Runton, have

since been referred to the earliest Pleistocene; Zeuner, 1959). Both

of these species are characterized by the closed anterior loop of M1

and closed third and fourth triangles on the M2. The living species

P. oaxacensis and P. guatemalensis also demonstrate these features,

and thus are relictual species of this earliest Pitymys radiation in

North America.

Pitymys Ilanensis is also recorded from the Cudahy fauna of Kansas,

and is separable from P. meadensis in that the anterior loop of MI is

open and triangles three and four of the M2 are confluent. The shallow

sixth reentrant angle and mesially directed anterior enamel border of

the fourth triangle of the MI indicate affinities with the living

P. ochrogaster, and I believe that P. llanensis is the ancestor of the

former species.

Pitymys involutus and P. dideltus of the Port Kennedy and

Cumberland Cave faunas are inadequately described and illustrated in

published accounts, and I have not studied these forms in detail. Both






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of these faunas are most likely of Irbingtonian age and somewhat younger

than the Cudahy fauna (Hibbard, 1958).

The extinct Pitymys arata and the living P. quasiater are related

to P. meadensis in possessing a closed anterior loop on the M,, but are

more advanced in that the third and fourth triangles of the M2 are con-

fluent. The sixth reentrant angle of the M1 in both these species is

deep and may curve up into the anterior loop. The anterior border of

the fourth triangle is usually sloped posteriorly as well. Both char-

acteristics indicate alliance with the line leading to Pitymys pinetorum.

Pitymys pinetorum individuals I have studied usually demonstrate

an open anterior loop on the M, (it is closed in a few P. p. nemoralis,

but I have not seen it closed in any other living P. pinetorum subspecies)

and triangles three and four of the M2 are open in all specimens I have

seen. These characteristics are first seen in a member of the P. pinetorum

line in the early Rancholabrean species from the Williston III deposit

of Florida, P. hibbardi (Holman, 1959). This species differs from P.

pinetorum in its larger size and reduced capsular process. The cap-

sular process is well developed in adult P. pinetorum. Pitymys hibbardi

may have been derived from the Coleman IIA P. arata.


Neofiber alleni

Material: UF 11785-11789; 1 femur, 1 humerus, isolated teeth.

Remarks: The fossil material is inseparable from Recent material with

which it was compared.






























Figure 9 .-- The dentition of Pitymys arata and Equus sp.

from the Coleman IIA fauna, and femora of

Lepus alleni and Lepus townsendii.




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