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B*1UIIN98
of the
FLORIDA
MUSEUM OF
NATURAL HISTORY
PALEONTOLOGY AND GEOLOGY OF THE
LEISEY SHELL PITS,
EARLY PLEISTOCENE OF FLORIDA
PART II
Richard C. Hulbert, Jr., Gary S. Morgan,
and S. David Webb, Volume Editors
Volume 37, Pt. II, Nos. 11-20, pp. 345-660 1995
UNIVERSITY OF FLORIDA
GAINESVILLE
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Publication date: March 14th. 1995
Price $30.00 per s
PALEONTOLOGY AND GEOLOGY OF THE
LEISEY SHELL PITS,
EARLY PLEISTOCENE OF FLORIDA
PART II
Richard C. Hulbert, Jr., Gary S. Morgan,
and S. David Webb, Volume Editors
PALEONTOLOGY AND GEOLOGY OF THE LEISEY SHELL
PITS, EARLY PLEISTOCENE OF FLORIDA
VOLUME 37, PART I
TABLE OF CONTENTS
11. Gravigrade xenarthrans from the early Pleistocene Leisey Shell Pit 1A,
Hillsborough County, Florida
H. Gregory M cDonald .................................... ... .......................... 345
12. The cingulates (Xenarthra) of Leisey Shell Pit 1A (Irvingtonian),
Hillsborough County Florida
Kevin F. Downing and Richard White.............................. ......................... 375
13. Small mammals (Insectivora, Lagomorpha, and Rodentia) from the early Pleistocene
(early Irvingtonian) Leisey Shell Pit Local Fauna, Hillsborough County, Florida
Gary S. Morgan and John A. White .............................................................397
14. Fossil carnivores from the Leisey Shell Pits, Hillsborough County, Florida
Annalisa Berta .............................. .......................... .........................463
15. The fossil record of Arctodus pristinus (Ursidae: Tremarctinae) in Florida
Steven D. Emslie.................................................. ............................501
16. The giant tapir, Tapirus haysii, from Leisy Shell Pit IA and other Florida
Irvingtonian localities
Richard C. Hulbert, Jr. .......................... ....... ........................ ....515
17. Equus from Leisey Shell Pit IA and other Irvingtonian localities from Florida
Richard C. Hulbert, Jr. ...................................... ............. ........... 553
18. Tayassuidae of the Irvingtonian Leisey Shell Pit Local Fauna,
Hillsborough County, Florida
David B. W right ........................................ .....................................603
19. Selenodont artiodactyls (Camelidae and Cervidae) from the Leisey Shell Pits
Hillsborough County, Florida
S. David W ebb and Frank G. Stehli ......................................................... ... 621
20. Proboscidea from Leisey Shell Pits, Hillsborough County, Florida
S. David Webb and Joseph P. Dudley...................................................645
GRAVIGRADE XENARTHRANS FROM THE
EARLY PLEISTOCENE LEISEY SHELL PIT 1A,
HILLSBOROUGH COUNTY, FLORIDA
H. Gregory McDonald1
ABSTRACT
Two taxa of ground sloths are present at Leisey Shell Pit 1A, Nothrotheriops texanus and
Paramylodon harlani. The Irvingtonian sample of Nothrotheriops is sufficiently distinct morphologically
to warrant separation from the Rancholabrean species, N. shastensis, and is referred to Nothrotheriops
texanus (Hay) (new combination). Individuals of the Irvingtonian P. harlani average smaller than those of
the Rancholabrean and there is a general size increase in the lineage from the Blancan to Rancholabrean with
only minor morphological changes. Use of Paramylodon instead of Glossotherium for the species P.
harlani is nomenclaturally correct.
RESUME
En la fauna local de la Excavaci6n de Conchuelas de Leisey se encuentran dos taxa de perezosos
terestres: Nothrotheriops texanus y Paramylodon harlani. La muestra Irvingtoniana de Nothrotheriops es
suficientemente diferente en terminos morfol6gicos como para permitir separarla de la bien conocida especie
Rancholabreana N. shastensis y es referida como Nothrotheriops texanus (Hay) (nueva combinaci6n). Los
Paramylodon del Irvingtoniano son mis pequefios que los del Rancholabreaense, existiendo un incremento
general de tamafo en el linaje desde Blancano a Rancholabraense, con s6lo pequeflos cambios morfol6gicos.
El uso del nombre Paramylodon en vez de Glossotherium, en el caso de la especie P. harlani, es correct en
t6rminos de nomenclature.
SThe author is a Paleontologist at the Hagerman Fossil Beds National Monument, P. O. Box 570. Hagennan, ID 83332-0570, U.SA.
MCDONALD, H. G. 1995. Gravigrade Xenarthrans from the early Pleistocene Leisey Shell Pit IA,
Hillsborough County, Florida. Bull. Florida Mus. Nat. Hist. 37 Pt. 11(11):345-373.
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II No. 11
INTRODUCTION
Among the diverse fauna from Leisey 1A are two ground sloths,
Paramylodon harlani and Nothrotheriops texanus. P. harlani has long been
known as a member of the Pleistocene fauna of Florida. By contrast, the presence
of Nothrotheriops has only recently been recognized in the state (McDonald 1985).
Rancholabrean records of both genera are common, but Irvingtonian age records
are rare. Thus the recovery of a large sample of both taxa from the Leisey 1A
locality adds significantly to our understanding of the evolution and biogeography
of these two animals.
ABBREVIATIONS
The following abbreviations are used: AMNH American Museum of Natural
History, New York, CI Albertson College of Idaho, Caldwell, FMNH Field
Museum, Chicago, IMNH Idaho Museum of Natural History, Pocatello, LACM -
Natural History Museum of Los Angeles County, Los Angeles, UF Florida
Museum of Natural History, Gainesville, USNM National Museum of Natural
History, Washington D.C., mm millimeters, cm centimeters, M mean, n-
number.
ACKNOWLEDGEMENTS
I would like to thank S. David Webb of the Florida Museum of Natural History for the opportunity to
study the sloths of the Leisey Shell Pit fauna and for his guidance and help in this and other projects. Gary S.
Morgan aided in numerous ways during my visits to the Florida Museum of Natural History. George
Jefferson and Chris Shaw have greatly aided my work during my visits to the Page Museum to examine the
collections from Rancho La Brea. Larry Barnes and David Whistler have graciously provided access to the
collections housed at the Natural History Museum of Los Angeles County. Clayton E. Ray kindly permitted
me to study specimens in his care at the Smithsonian. Mary Ellen Aheam photographed the specimens, and
Wendy Zomlefer prepared the illustrations. The efforts of both are greatly appreciated. Les R. Kleinberg
greatly helped by measuring mandibles ofParamylodon from Rancho La Brea. Elaine Anderson, Gerry de
luliis, Richard C. Hulbert, Jr., and Gary S. Morgan kindly reviewed the manuscript A special word of
thanks is extended to C. E. "Bud" Leisey,Jr., and Eric Hunter who generously aided the project in many
ways. Excavation of the site was conducted by numerous members of the Tampa Bay Gem and Mineral
Society, without whose help this important fauna could not have been saved. JoAnn Norris typed the
manuscript. Partial funding for the study of the sloths was provided by a grant from Leisey Shell Pit Inc. to
the Florida Museum of Natural History.
MCDONALD: GRAVIORADE XENARTHRANS FROM LEISEY SHELL PIT 1A
SYSTEMATIC PALEONTOLOGY
Order XENARTHRA Cope 1889
Family MEGATHERIIDAE Owen 1843
Subfamily NOTHROTHERINAE Kraglievich 1923
Nothrotheriops texanus (Hay 1916) new combination
Nothrotherium texanum Hay 1916.
Nothrotherium shastense Sinclair 1905. Lull 1929 (in part).
Nothrotheriops shastensis (Sinclair 1905). McDonald 1985 (in part).
Type Specimen.- USNM 8353, incomplete cranium.
Type Locality.- Wheeler County, Texas (see Hay 1916).
Referred Leisey 1A Specimens.- UF 86885, 80108, 84464, 86119, 86120,
86980, 86981, 86982, 86983, crania; 64348, 64349, 86899, 86121, 84626, 80314,
83100, 83594, 83900, 86984, 86985, mandible; 86185, 86987, 86989, 86990,
86991, humerus; 65821, 84463, 86996, 86999, 86997, 87000, ulna; 65821, 86168,
86992, 86993, 86994, 86995, radius; 87003 coossified third and fourth
metacarpals; 87010, fifth metacarpal; 81500, 86733, 80038, 64350, 84931, 86355,
80211, 81362, 87012, femur; 67354, 64353, 86973, 87013, 87014, tibia; 87017,
patella; 65824, 82938, 84449, 87028, calcaneum; 64335, 86891, 84448, 87026,
87027, astragalus; 86837, 87018 83688 coossified entocuneiform and first
metatarsal; 65822, 64367, 81502, 87020, 87019, metatarsal II; 65823, 84287,
87021, 87022, metatarsal m; 87882, 86969, 87023, 87024, 86306, 86882,
metatarsal IV; 87025, metatarsal V; 86952, 86870, 67127, 87035 coossified
proximal and second phalanx, digit 3 pes.
Emended Diagnosis.- Smaller than Nothrotheriops shastensis with more
gracile cranium. Alveolar length of maxilla less than predental length of maxilla
in contrast to N. shastensis in which the alveolar length of the maxilla is equal to
or greater than the predental length of the maxilla. Total alveolar length of the jaw
is less than 50% of the length of the mandibular spout (measured from the anterior
edge of the first cheek tooth to the anterior edge of the spout) in contrast to N.
shastensis in which total alveolar length is equal to or greater than 50% of the
spout length.
Description.- Comparison of both adults and juveniles from Leisey IA,
which contains a minimum number of eight individuals, was made with specimens
of late Pleistocene (Rancholabrean) Nothrotheriops shastensis from San Josecito
Cave, Nuevo Leon, Mexico and Rancho La Brea, California. Since the skeletal
anatomy of the Leisey IA N. texanus is essentially the same as N. shastensis, the
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, No. 11
reader is referred to Stock (1925) or Lull (1929) for specific descriptions of bones
and to Paula Couto (1974) for the manus. Rather than reiterate their excellent
descriptions, references to specific bones will be made only in a general way.
Crania of Nothrotheriops from Leisey 1A display only a few differences from
those from Rancho La Brea (Fig. 1). Overall length is similar in both species but
the relative dimensions of other parts of the skull differ. One difference is the
relationship between cheek tooth row length and predental length of the maxilla
(Fig. 2). Alveolar length is shorter than the predental length in the Leisey 1A
sample (73, 79, 84, and 89%) whereas in the Rancho La Brea sample of N.
shastensis alveolar length of the maxilla is greater than that of the predental length
(100, 119, 128 and 129%). Alveolar length of the maxilla is 91% of predental
length in the type of Nothrotheriops texanus (USNM 8353).
In length and relative proportions, the skulls of the two samples are closely
comparable in most respects. Nevertheless, the Leisey IA sample is consistently
smaller than the Rancholabrean sample in many transverse dimensions. This
combination of similar length but smaller transverse dimensions gives the skull of
Nothrotheriops texanus from Leisey IA a more gracile appearance. These
dimensions in the holotype ofN. texanus are more similar to those from Rancho La
Brea and San Josecito than to Leisey 1A specimens except in the relative
proportions of the maxilla discussed above. The intermediate size of the holotype
of N. texanus suggests that it probably represents a later population than that from
Leisey lA.
Although the length of the predental portion of the maxilla is different in the
two species, the width of this portion of the skull remains the same. This gives the
anterior part of the skull of N. shastensis the appearance of having a shorter and
stouter rostrum than N. texanus. The relative increase in the total alveolar length
of the maxilla from N. texanus to N. shastensis has no affect on the width of the
rostrum.
Comparison of the Leisey 1A Nothrotheriops mandibles (Fig. 3A) with those
from Rancho La Brea and San Josecito Cave indicate some differences. Specimens
from Leisey IA are smaller (Figs. 4, 5) than those from later deposits. Despite the
smaller size, the ratio of total alveolar length to maximum depth of the jaw
(usually below the third molariform) is essentially the same (Leisey IA: 0.96-1.08,
M = 1.01, N = 6; Rancho La Brea and San Josecito 0.83-1.06, M = 0.99, N = 8).
The relationship between alveolar length and mandibular spout length differs
between the two samples (Fig. 5). Three specimens from Leisey IA had total
alveolar lengths of 39, 45 and 46% of the mandibular spout. The combined sample
from Rancho La Brea and San Josecito Cave (N = 7) had an alveolar length from
52 to 59% (M = 55%) of the length of the mandibular spout. This relative increase
in the total alveolar length compared to the mandibular spout length parallels the
relative increase in the total alveolar length of the maxilla compared to its
predental length.
One right juvenile maxilla (UF 83700) is interesting because of the presence
of an atavistic caniniform (Fig. 6). Primitive nothrotheres such as Hapalops and
MCDONALD: GRAVIGRADE XENARTHRANS FROM LEISEY SHELL PIT IA
10cm
Figure 1. Skull ofNothrotheriops texanus, UF 86885, in (A) dorsal, (B) lateral and (C) ventral views.
350 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, No. 11
70
I mm PREDENTAL LENGTH
0 ALVEOLAR LENGTH
4 65
<^ _PREDENTAL LENGTH >
A LVEOLA ALVEOLAR LENGTH
.-J 0
J 60o
x o
5 S 55
ZLL
o 50
W
X 45
45 50 55 60 65 70mm
ALVEOLAR LENGTH OF MAXILLA
Figure 2. Comparison of predental length of maxilla against total alveolar length of maxilla in
Nothrotheriops texanus and Nothrotheriops shastensis. Open circle = Leisey, solid circle = type N.
texanus, solid square = N. shastensis.
Pronothrotherium, are characterized by the presence of upper and lower
caniniforms. Some of the later nothrotheres such as Nothrotherium and
Nothrotheriops, have lost the caniniforms although another Pleistocene genus,
Nothropus, retained them. The caniniform is separated from the cheek tooth by a
diastema and is positioned halfway between the anteriormost cheek tooth and the
anterior edge of the maxilla. The caniniform in UF 83700 is strongly curved with
its base positioned above the root of the first cheek tooth. The tooth is small
measuring only 4.0 by 2.8 mm. Orientation of the long axis is anteroposteriorly.
The occlusal surface is broken so it is not possible to tell if there is any wear
suggestive of a complimentary lower caniniform. None of the recovered jaws of
juveniles have any indication of a lower caniniform.
Coossification of adjacent bones of the manus and pes is a common feature in
ground sloths, especially fusion between the entocuneiform and first metatarsal.
Stock (1925) described two specimens from Rancho La Brea in which these two
bones are fused, and the sample from San Josecito Cave contains 20 left and 8
right examples of this fusion. Three specimens from Leisey 1A (UF 86837, 87018
and 83688), two left and one right, show the coossification of the entocuneiform
and first metatarsal. These bones are also fused in the other late Pleistocene
nothrothere genus, Nothrotherium (Paula Couto 1971), but they are separate in
early nothrotheres, such as Hapalops. Since Nothrotheriops is unknown prior to
its appearance in the Irvingtonian of North America, it is not possible to determine
when the ungual and proximal phalanx were lost and the entocuneiform and first
metatarsal coossified. A mounted skeleton of Pronothrotherium typicum of
MCDONALD: GRAVIGRADE XENARTHRANS FROM LEISEY SHELL PIT IA
10 cm
Figure 3. (A)Nothrotheriops texanus, UF 86899, lateral view of mandible. Paramylodon harlani, UF
80367, (B) occlusal view and (C) lateral view of mandible.
Pliocene age in the Field Museum (FM 14503) has lost the ungual phalanx, but the
entocuneiform and vestigial first metatarsal are still unfused.
Another common coossification of two bones is the proximal and middle
phalanx of the third digit of the pes. The two phalanges are separate in Miocene
Hapalops, but are fused in many later sloths. Four specimens from the Leisey 1A
locality exhibit the fused condition; UF 86952, 86870, 67127 and 87035. These
352 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, No. 11
m 65
1 mm
60
55 0
0
LL 51 1
0 50
I o(9
45 o o
LU 40
0 42 44 46 48 50 52 54 56 58 60mm
ALVEOLAR LENGTH OF MANDIBLE
Figure 4. Comparison of total alveolar length of mandible against depth of mandible at third molarifonn in
Nothrotheriops texanus from Leisey IA (open circle) and Nothrotherops shastensis (open square).
two bones are also fused in Nothrotherium. This feature seems to have been
established early in the nothrotheres as they are already coossified in
Pronothrotherium typicum (FM 14503) of Huayquerian and Montehermosan (early
to middle Pliocene) age. In contrast these two bones do not fuse in the
megalonychid, Megalonyx, until the late Pleistocene (McDonald 1977).
A pathological coossification of the right third and fourth metacarpals (UF
87003) is represented in the Leisey IA sample. The area of fusion is restricted to
the proximal end and excess bone tissue is present on the dorsal surface of both
bones.
A single fifth metacarpal (UF 87010) was recovered. It differs from late
Pleistocene forms in being more gracile. A similarly gracile fifth metacarpal was
described from the Irvingtonian age Pool Branch, Florida locality by McDonald
(1985).
Postcranially the skeleton of the Leisey 1A Nothrotheriops and other
Irvingtonian specimens tend to be smaller than those from the Rancholabrean.
This is shown by various plots for the humerus (Fig. 7). This separation does not
hold as well for the femur (Fig. 8). A major impediment to a more accurate
analysis of size trends in the post-cranial skeleton is the absence of the same bone
from the various localities, so comparable samples are small. In many of the
localities listed in Table 1, Nothrotheriops is represented by a single bone.
However, based on the sample available from Leisey 1A, it does not appear that the
size increase of Nothrotheriops from the Irvingtonian to Rancholabrean was as
great as in Paramylodon harlani over the same period of time.
MCDONALD: GRAVIGRADE XENARTHRANS FROM LEISEY SHELL PIT IA
65
I mm
z -.
u CD 55
cc rz
2 45 0
0
> O
ss
35
85 90 95 100 105 110 115mm
SPOUT LENGTH
Figure 5. Comparison of length of mandibular spout anterior to first molariform against total alveolar length
of mandible in Nothrotheriops texanus (open circle) and Nothrotheriops shastensis (solid circle). Line
represents ratio of 2:1 for spout length against alveolar length.
Figure 6. Nothrotheriops texanus right maxilla ofjuvenile, UF 83700, showing atavistic presence of
caninifonn (indicated by arrow). Scale bar 20 mm in length.
Discussion.- Hay (1916) based Nothrotherium texanum on an incomplete
cranium (USNM 8353) recovered from a well in Wheeler County, Texas. He
distinguished it from Nothrotherium graciliceps (= N. shastense) (Stock 1913),
also based on a skull, on a number of morphological features. No comparison was
made with N. shastense Sinclair (1905), since it was based on an edentulous
mandible and 14 isolated teeth. Stock (1925) made N. graciliceps a subspecies of
N. shastense. Lull (1929) reviewed the genus in his study of a mummified
specimen from New Mexico and considered Nothrotherium texanum to be
353
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. IL No. 11
170
mm
160
150
1401
34
(J __ (9_
0
360 380 400 420 440 mm
LENGTH OF HUMERUS
Figure 7. Comparison of humerus length against distal width across epicondyles in Nothrotheriops texanus
(circle) and Nothrotheriops shastensis (square).
200
mm
190
180
170
330
0 E 1
350
370
390
410mm
LENGTH OF FEMUR
Figure 8. Comparison of femur length against mediolateral width of proximal end in Nothrotheriops
texanus (circle) and Nothrotheriops shastensis (square).
synonymous with N. shastense. Since Lull's work it has generally been accepted
that there is a single North American species, N. shastense. Hoffstetter (1954)
proposed that the North American nothrothere was subgenerically distinct from the
South American species and established the subgenus Nothrotheriops. Paula
MCDONALD: GRAVIGRADE XENARTHRANS FROM LEISEY SHELL PIT 1A
Table 1. Irvingtonian records ofParamylodon harlani andNothrotheriops texanus. Unpublished
specimens are in the following collections: CI = College of Idaho; IMNH = Idaho Museum of Natural
History; LACM = Los Angeles County Museum; UF = Florida Museum of Natural History, USNM =
United States National Museum. Numbers in front of each locality refer to the localities on the map in
Figure 15.
Paramylodon Nothrotheriops
Locality harlani texanus Reference
California
1. Irvington X X Savage 1951
Alameda Co
2. Vallecito Creek X X Downs and White 1968
San Diego Co.
Florida
3. Haile 16A X UF
Alacua Co.
4. Inglis IA X Webb 1974
Citrus Co.
5. Leisey 1A X X Thispaper
Hilsborough Co.
6. Pool Branch X McDonald 1985
Polk Co.
Idaho
7. Oreana X CI
Owyhee Co.
Kansas
8. Adams X Hibbard and Taylor 1960
Meade Co.
9. Courtland Canal X Eshelman and Hager 1984
Jewell Co.
10. Kanopolis X Hibbard et al. 1978
Ellsworth Co.
11. Sandahl X Semken 1966
McPherson Co.
Nebraska
12. Angus X Schultz and Martin 1970
Nuckolls Co.
13. Gordon X Schultz and Stout 1948
Sheridan Co.
14. Hay Springs X Allen 1913; Brown 1903
Sheridan Co. (Type Locality for Paramylodon nebrascensis and Mylodon garmani)
Oklahoma
15. Curtis X X Akersten and McDonald 1991
Woodward Co.
16. Holloann X Dalquest 1977
Tillman Co.
Oregon
17. Rome X IMNH
Malheur Co.
Pennsylvania
18. Port Kennedy Cave X Cope 1899
Montgomery Co.
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, No. 11
Table 1 Continued.
Locality Paramylodon Nothrotheriops Reference
harlani texanus
Texas
19. Gilliland X Hibbard and Dalquest 1966
Baylor and Knox Cos.
20. Rock Creek X Lull 1915
Briscoe Co.
21. Wheeler Co. X Hay 1916
(Type Locality Nothrotheriops texanus)
Washington
22. Delight X Matthew 1902
Adans Co.
Mexico
23. El Golfo X Shaw 1981
State of Sonora
Canada
24. Medicine Hat Fauna 9 X Harington 1978
Province of Alberta
Couto (1971) reviewed the North and South American forms and raised
Nothrotheriops to generic status.
There does not seem to be any reason to believe that there is more than a
single lineage of North American nothrothere. They appear in the early
Pleistocene (Irvingtonian) and culminate in the Rancholabrean species
Nothrotheriops shastensis. The question then arises as to the value of subdividing
this lineage and formally recognizing an earlier evolutionary stage as a separate
species.
In the continuum of an evolving lineage, it is difficult and somewhat arbitrary
to demarcate the boundaries distinguishing two species. Smaller samples may
show a marked separation in size or proportions which disappear as the sample
size increases. Three of the criteria used here to distinguish N. texanus from N.
shastensis; size, ratio of alveolar to predental length of maxilla, and ratio of
alveolar length to length of mandibular spout--may blend as intermediate
populations are found. However, since these criteria serve clearly to distinguish
the two forms, use of a distinct binomen serves the practical purpose of identifying
the earlier evolutionary stage of the lineage and thus aiding in the identification of
the age of the fauna with which it is associated. The type of Nothrotheriops
texanus is distinguishable from N. shastensis and falls easily within the range of
the Leisey IA sample. Other Irvingtonian samples are also referred to N. texanus
based primarily on their smaller size. At this time all referred material of N.
texanus occurs in the Irvingtonian and N. shastensis is exclusively Rancholabrean.
The timing of the transition of N. texanus to N. shastensis is currently unknown
MCDONALD: GRAVIGRADE XENARTHRANS FROM LEISEY SHELL PIT IA
and must await the recovery of intermediate cranial or mandibular material from
known age faunas.
Family MYLODONTIDAE Gill 1872
Genus Paramylodon Brown 1903
Type Species.- P. nebrascensis Brown 1903 (= Mylodon harlani Owen
1840).
Discussion.- There has been a common trend in the recent literature to refer
the North American species harlani to the genus Glossotherium (Kurten and
Anderson 1980). I have not followed this usage but rather have retained the older
binomen, Paramylodon harlani. A short synopsis of the history of these names
will demonstrate the nomenclatural problems involved.
Owen (1840) described Mylodon darwinii based on a complete mandible and
Glossotherium based on a left temporal. Glossotherium originally was not used in
a binomen. Owen (1842) described a second species of Mylodon, M. robustus. In
a footnote in this same publication, Owen (1842:154) considered Glossotherium to
be the same as Mylodon darwinii, the type species for Mylodon. Harlan (1831)
described and figured a mandible from Big Bone Lick, Kentucky which he referred
to his previously described Megalonyx laqueatus. This paper was later republished
by Harlan (1835). The mandible was that of a mylodont, not a megalonychid, and
Owen (1840; 1843) recognizing its affinities, proposed the species harlani which
he placed in his genus Mylodon. This resulted in three species being recognized
for the genus Mylodon (Leidy 1855). One, and possibly two, of these species
represented other genera. Recognizing that more than one genus was represented,
Reinhardt (1879) proposed the genus Grypotherium to replace Mylodon for the
binomen Mylodon darwinii. Additional confusion arose from considering the
species robustus to be the type species for Mylodon and placing darwinii in the
genus Glossotherium (Ameghino 1889; Lydekker 1894). Kraglievich (1928),
assuming that Glossotherium had no species attached to it, proposed the name
Glossotherium uruguayense as the type species for Glossotherium, utilizing the
temporal described by Owen as the type.
Brown (1903) established the genus Paramylodon, with the type species, P.
nebrascensis. Unfortunately, many workers considered harlani to be the type
species ofMylodon rather than darwinii (Stock 1914a, b, 1917, 1925) and felt that
there were two North American mylodonts; Mylodon harlani and Paramylodon
nebrascensis. Eventually the convention of recognizing a distinct genus for each
species developed; Mylodon darwinii, Glossotherium robustum and Paramylodon
harlani (Kraglievich 1928). During this time other species had been described for
each of these genera or under a genus proposed as a substitute for an earlier name;
for example, Eumylodon chapadmalensis (Kraglievich 1925) which later became
Glossotherium chapadmalense (Kraglievich 1928). Hoffstetter (1952) used
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, No. 11
Paramylodon as a subgenus of Glossotherium. Cartelle (1980) and Cartelle and
Fonseca (1981) resurrected the name Ocnotherium Lund 1842 as a subgenus of
Glossotherium. Given the date of publication of this name, Ocnotherium may be
the next available name for South American species currently placed in
Glossotherium should the name Glossotherium be considered invalid.
Despite this maze of nomenclatural proposals, there has been very little
discussion of the morphological features that distinguish the various genera or the
various species grouped within a particular genus. There has certainly been little
consideration of evolutionary or phylogenetic relationships of the various taxa and
the change in relationships implied by the changing of names. None of the
previous studies have demonstrated that Paramylodon should be considered a
junior synonym of Glossotherium. Using the genus Glossotherium for the North
American species harlani is of dubious value (I would even question retaining it as
a valid genus). I recommend continued use of the name Paramylodon harlani for
Irvingtonian and Rancholabrean specimens of North American mylodonts. Use of
the genus Paramylodon recognizes the geographic isolation and separate evolution
of this lineage from the South American mylodonts. In an attempt to avoid further
nomenclatural confusion I have followed Robertson (1976) in recognizing the
North American Blancan mylodont as "Glossotherium" chapadmalense. This
usage recognizes the ancestor-descendant relationship of the two forms and is with
the full realization that further study of the relationships between the North and
South American mylodonts is needed.
Paramylodon harlani (Owen 1840)
Mylodon harlani Owen 1840. Owen 1842 1843; Leidy 1855; Stock 1914a, 1914b,
1917, 1925.
Oryctotherium missouriense Harlan 1841. Perkins 1843.
Oryctotherium oregonense Perkins 1843.
Eubradys antiquus Leidy 1853
Megalonyx potens Leidy 1853
Mylodon sodalis Cope 1878
Mylodon renidens Cope 1895
Mylodon sulcidens Cope 1895
Paramylodon nebrascensis Brown 1903
Mylodon garmani Allen 1913
Mylodon tenuceps Stock 1917
Mylodon harlani tenuceps Stock. Stock 1925
Paramylodon harlani (Owen). Kraglievich 1928
Glossotherium (Paramylodon) harlani (Owen)., Hoffstetter 1952
Glossotherium harlani Kurt6n and Anderson 1980
Type Specimen.- Partial right mandible, New York Lyceum, now missing.
MCDONALD: GRAVIGRADE XENARTHRANS FROM LEISEY SHELL PIT 1A
Type Locality.- Big Bone Lick, Boone County, Kentucky (see Harlan 1831).
Referred Specimens.- Leisey 1A: UF 83769, 64400, 64373, crania; 87039-
87042, 67426, 80215, 80911, 83791, 83983, 84077, 86158, 80215, isolated upper
caniniform; 87051, 87070, 87058, 67427, 86379, 86739, 86738, 83337, 80778,
80779, M2; 80367, 83335, 87048, 87047, 87037, 84750, 64357, 87046, 87038,
87045, 87044, 87043, 80912, 84848, 80214, mandibles; 67436, 87054, 67437,
80895, 80531, 81216, 87063, 86767, 87065, 95880, isolated lower first
molariform; 86846, 87045, 87044, 87043, 80912, 82004, 67446, isolated lower
fourth molariform; 84136, 82933, 65851, 65855, 65856, 64364, humerus; 65857,
ulna; 80163, radius; 65830, 65828, 65829, metacarpal I; 64368, 81791, metacarpal
II; 65831, metacarpal m; 87024, metacarpal IV; 82245, metacarpal V; 80109,
81716, 64361, 80776, 63859, 80039, 80164, 87087, femora; 65860, 64365, 65862,
65861, 80176, 86930, tibiae; 64366, 87100, astragali; 65832, 82658, metatarsal II
and mesocuneiform; 87105, 83986, metatarsal III; 65833, 83984, metatarsal V.
Description.- The large sample from Leisey IA, like that from Rancho La
Brea, permits an evaluation of the morphological variation that may be
encountered in North American mylodonts. When compared with the Rancho La
Brea and other samples, it permits the evaluation of evolutionary trends.
Except for its smaller size and a few minor differences, the skeletal anatomy
of P. harlani from Leisey 1A resembles that of the sample from Rancho La Brea,
which is well described in Stock's (1925) classic monograph. Discussion of the
sample from Leisey 1A is restricted here to variation and evolutionary trends.
One evolutionary trend in Paramylodon harlani is the tendency to reduce or
lose the anterior tooth of the upper dentition (= caniniform). Loss of this tooth
parallels a similar loss in Mylodon darwinii. Loss of the upper caniniform was
used by Brown (1903) in the diagnosis of the genus Paramylodon. Stock (1925)
noted that in a sample of 45 skulls from Rancho La Brea, 21 had the first tooth on
both sides, 14 had the tooth absent on both sides, 7 had the tooth on either the right
or left side and 3 were doubtful regarding the condition.
The Leisey IA sample has six specimens which preserve the anterior portion
of the palate where this tooth is located (Fig. 9). Some have the tooth in place, and
others have an open alveolus. Twelve isolated upper caniniforms were recovered.
Unlike the Rancho La Brea sample all of these caniniforms are large with well
developed occlusal surfaces. Based on the Leisey lA sample it appears that the
caniniforms had not experienced any reduction in the early Pleistocene. This
observation is confirmed in several other early Pleistocene samples.
Prominent caniniforms are also present in Paramylodon harlani from the
earlier Inglis IA and Haile 16A faunas of Florida. Unfortunately, neither of these
samples is as large as that from Leisey 1A. Specimens from Irvingtonian localities
outside of Florida, such as Rock Creek, Texas (Lull 1915), and Hay Springs,
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II No. 11
C10 cm
10 cm
Figure 9. Skull ofParamylodon harlani, UF 83769, in (A) dorsal, (B) lateral and (C) ventral views.
MCDONALD: GRAVIGRADE XENARTHRANS FROM LEISEY SHELL PIT 1A
Nebraska (the type locality for Mylodon garmani [= P. harlani] [Allen 1913] also
have prominent caniniforms. A partial palate from Rome, Oregon has alveoli for
both caniniforms.
The holotype of Paramylodon nebrascensis (AMNH 2780) is one possible
exception to the pattern that all Irvingtonian Paramylodon have both upper
caniniforms. Brown's (1903) diagnosis of Paramylodon was based partially on the
absence of the first upper tooth (=caniniform). However, the holotype was actually
found near Hay Springs. Thus, it may not be part of the Hay Springs fauna proper,
but from younger deposits.
Supporting evidence for the presence of a caniniform in all the individuals of
Paramylodon from the Leisey lA fauna is provided by the first lower cheek tooth.
All specimens (12), both isolated and those still in the mandible, display a double
wear surface reflecting occlusion against the upper caniniform anteriorly and the
first upper molariform posteriorly. Specimens lacking the upper caniniform, such
as the holotype of P. nebrascensis, have a lower first molariform with a wear
surface only on the posterior side of the tooth.
There are two morphs of the upper caniniform represented in the sample from
Leisey 1A (Fig. 10). The first form develops an occlusal surface at an angle
oblique to the long axis of the tooth. The occlusal surface of the second morph
develops perpendicular to the long axis of the tooth, so that the occlusal end of the
tooth appears truncated. In the second morph the occlusal surface reflects the
shape of the tooth's cross-section. The radius of curvature of the two morphs is the
same, but the dimensions of the tooth anteroposteriorly and mediolaterally are
larger in the first morph (Fig. 11). The occlusal surface of both morphs bear
prominent dorsoventral striae and less prominent mediolateral striae. Caniniforms
from Inglis IA (3 specimens) and Haile 16A (1 specimen) include only the larger
morph with the obliquely worn occlusal surface. The type of Mylodon garmani has
upper caniniforms that are worn nearly perpendicular to the long axis of the tooth
and has a smaller cross-sectional area.
Both morphs are present in the sample from Rancho La Brea, with nine
specimens showing oblique wear and five perpendicular wear. Mean size for the
Rancho La Brea population is smaller than that of the Leisey IA population for
both morphs (Fig. 11). There does not appear to be any significant difference in
the dimensions of the two morphs from Rancho La Brea but the size difference in
the Leisey sample is more noticeable. Those with oblique wear from Rancho La
Brea have an anteroposterior (AP) length of 17.3 3.2 mm and mediolateral
dimension (ML) of 14.3 1.1 mm, N = 8; while the caniniform with perpendicular
wear has an AP dimension of 17.2 3.1 and an ML width of 14.6 1.0 mm, N =
5. In the Leisey 1A sample the values are 23.8 3.1 mm for AP and 15.5 2.2
mm for ML for caniniforms with oblique wear, N = 6; and 19.2 1.6 for AP
length and 13.9 0.47 mm for ML width, N = 5, for caniniforms with
perpendicular wear.
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. I, No. 11
Figure 10. Lateral view of upper caniniforms ofParamylodon harlani showing (A) oblique (UF 87042)
and (B) perpendicular (UF 87039) occlusal wear morphologies. Scale bar 10 nun in length.
Stock (1925, fig. 66) illustrated a series of right lower fourth molariforms
showing variation in the shape of the occlusal surface. In the Leisey IA sample,
14 lower fourth molariforms of both juveniles and adults are preserved. Since
sloths lack deciduous teeth, both juveniles and adults can be compared since size is
the only difference. A variation in the lower fourth molariform present in the
Leisey IA sample not illustrated by Stock is the presence of an accessory lobe on
the lateral side of the isthmus connecting the anterior and posterior lobes of the
tooth. This lobe is absent in three specimens, slightly developed in five
individuals, prominent in five and in one specimen, UF 82004, there are two lobes
(Fig. 12). Another individual, UF 87038, lacks the lobe on the isthmus but has an
additional lobe on the posterolateral corner of the anterior lobe of the tooth. The
presence of a prominent lobe is reflected in the outline of the alveolus so that even
mandibles which have lost the fourth molariform will indicate its occurrence.
MCDONALD: GRAVIGRADE XENARTHRANS FROM LEISEY SHELL PIT IA
25
mm
20
15
*
A 41
10L
10
A
A AA
A
.o aa
15 20
30mm
ANTEROPOSTERIOR LENGTH
Figure 11. Comparison of anteroposterior and mediolateral dimensions of upper caniniforms of
Irvingtonian (open symbols) and Rancholabrean (closed symbols) Paramylodon harlani. Triangle indicates
oblique wear, circle indicates perpendicular wear.
1cm
Figure 12. Outline drawings of occlusal surface of lower fourth molariform of Paramylodon harlani
showing variation in presence of extra columns. (A) UF 80367, (B) UF 67446, (C) UF 82004, (D) UF
83335.
As the cheek teeth of ground sloths lack a distinct crown, and are rootless and
grow continuously, it is difficult to directly determine the degree of hypsodonty by
the usual methods (Janis 1988; Janis and Fortelius 1988). However, the maximum
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, No. 11
depth of the mandible below the last cheek tooth relative to the alveolar length of
the tooth row of the mandible can be used to establish an "index of hypsodonty" for
ground sloths, which reflects a relative greater increase in tooth height relative to
an overall increase in size. As the height of the cheek teeth in ground sloths
increases, the depth of the jaw increases, but the overall length of the tooth row
does not change. Therefore, the depth of the jaw is less than the length of the tooth
row in sloths with less hypsodont teeth whereas the depth of the jaw (as measured
below the last cheek tooth) becomes greater than length of the tooth row in sloths
with more hypsodont teeth. Examination of changes in this index in which the
depth of the mandible increases without any change in overall body size can thus
be used to possibly identify changes in diet from less to more abrasive foods, or, as
was suggested by Janis (1988), a possible shift in habitat preference from closed to
more open habitat.
Such a change accounts for one of the differences that exists between the
Irvingtonian and Rancholabrean samples of Paramylodon harlani. Irvingtonian
specimens have a relatively shallower mandible relative to the alveolar length than
Rancholabrean specimens (Fig. 13). This relatively deeper mandible in
Rancholabrean Paramylodon is not formed as in Nothrotheriops in which the
relatively greater depth of the jaw is the result of an allometric change due to an
increase in size (Fig. 4) but rather the deepening of the mandible is greater than
that expected as resulting from an increase in size. Both the Blancan
"Glossotherium" chapadmalense and Irvingtonian specimens of P. harlani have
similar proportions of the mandibular depth to alveolar length. Yet Rancholabrean
individuals of P. harlani have relatively deeper mandibles than individuals of
Irvingtonian age with similar length tooth rows. This deepening of the mandible
allows the teeth to be taller overall and thus aids in compensating for increased
wear caused by feeding on abrasive food, whether or not the abrasion is due to
factors intrinsic or extrinsic to the plants consumed. Stock (1925) interpreted
Paramylodon as a grazer and inhabitant of open country, and it appears that from
the Irvingtonian to the Rancholabrean this ground sloth made a shift to greater
hypsodonty which allowed it to make better use of this niche or to shift from closed
to more open country.
Stock (1925) reported that only 2 out of 20 specimens from Rancho La Brea
had the mesocuneiform fused with the second metatarsal. Two specimens from
Leisey 1A, UF 65832 and 82658, have this condition. Unfused mesocuneiforms or
second metatarsals are not represented in the Leisey IA sample. Neither element
is preserved in the skeleton of "Glossotherium" chapadmalense (UF 10922) from
Haile 15A, so the condition of the Blancan predecessor is unknown. The
possibility exists that these two bones were unfused in "G." chapadmalensis, and
that this digit may have born an ungual, a feature lost in later species such as P.
harlani and G. robustum.
There is a noticeable size difference between "Glossotherium" chapadmalense
in the Blancan and Paramylodon harlani in the Rancholabrean. The gap is
bridged by a graded series of specimens of P. harlani in the Irvingtonian. Samples
MCDONALD: GRAVIGRADE XENARTHRANS FROM LEISEY SHELL PIT IA
120
W mm
-J
m 110 0 *
z 100 *o
2 90 *
U ** 0o
0 80 0
I
70 o
a-
o 60 -
90 100 110 120 130 140 150 160 170mm
ALVEOLAR LENGTH OF MANDIBLE
Figure 13. Comparison of alveolar length and depth of mandible in Rancholabrean, Irvingtonian and
Blancan mylodonts. Blancan "Glossotherium" chapadmalense (open square), Irvingtonian Paramylodon
harlant (open circle), and Rancholabrean P. harlani (solid circle).
of Irvingtonian P. harlani are not large enough to quantify the size change. It can
nevertheless be indicated in a simplistic way for certain abundant elements. A
series of astragali (Fig. 14) from different Florida faunas demonstrate the gradual
increase in size. The sequence of these faunas was independently determined
using the biochronology of other species present (see Morgan and Hulbert this
volume). This gradational sequence blurs the distinction between "G."
chapadmalense and P. harlani when based on size alone. A careful reevaluation of
the morphological features which distinguish the two taxa is therefore needed.
Such a reevaluation, however, must await a larger sample of Blancan and very
early Irvingtonian mylodonts.
PALEOECOLOGY
Juvenile Representation.- The samples of both Nothrotheriops and
Paramylodon include juveniles as indicated by limb bones lacking epiphyses,
incompletely fused cranial bones, or isolated teeth that are conical. The juvenile
characteristics of the Paramylodon sample are more strikingly displayed than those
of the Nothrotheriops sample. This is indicated-in Paramylodon by the presence of
mandibles with conical teeth. Sloth teeth are markedly expanded basally during
early stages of their eruption. They generally have become parallel-sided,
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, No. 11
A
C
Figure 14. Left astragalus of(A) "Glossotherium" chapadmalense and (B-C) Paramylodon harlani
showing increase in size. (A) Haile 15A (Blancan), UF 10922; (B) Leisey IA (early Irvingtonian), UF
64366; and (C) Hornsby Springs (Rancholabrean), UF 4035. Scale bar 50 mm in length.
however, prior to fusion of the epiphyses of the limbs and the presence of conical
teeth indicates an extremely young individual. In the Leisey sample there are a
number of juvenile Paramylodon jaws with conical teeth. On the other hand,
juvenile mandibles of Nothrotheriops are recognized on the basis of their smaller
size and porous texture of the bone, but all specimens have parallel-sided teeth. It
is not clear whether nothrothere teeth progress more rapidly that those of
mylodonts, or whether there is some taphonomic bias against younger nothrotheres
at the Leisey site.
At the time of deposition of Leisey IA, four species of ground sloth were
present in Florida: Megalonyx wheatleyi, Eremotherium n. sp., Nothrotheriops
MCDONALD: ORAVIGRADE XENARTHRANS FROM LEISEY SHELL PIT 1A
texanus and Paramylodon harlani. Yet only the latter two species were recovered
from this deposit, and they were quite richly sampled. Their abundance, as well as
the absence of Megalonyx and Eremotherium, reflects the local environment and is
not an artifact of small sample size.
Distribution of Eremotherium in the United States is restricted to the Gulf
and southern Atlantic coastal plains. The few inland records of this species are
from riverine deposits, suggesting that the invasion inland was facilitated by the
river, but limited to gallery forests. A similar distribution pattern occurs in South
America where the genus is found along the coast or lowlying coastal plains.
Eremotherium has generally been interpreted as a browser. This is confirmed by
the recovery from the tar seeps of Peru and Ecuador of cut twigs, whose length
matches the distance between the transverse lophs of eremothere teeth (A.G.
Edmund pers. comm.). Absence of Eremotherium from the deposit cannot be
attributed to its antiquity, since the genus is present in the older Inglis 1A, DeSoto
Shell Pit, and Haile 7C faunas (Webb 1974; Morgan and Hulbert, this volume).
Specimens of Eremotherium were collected at the Leisey Shell Pit (but not the
Leisey 1A site). In fact, Eremotherium was the most common ground sloth from
the Leisey Shell Pit 3 quarry, located only 0.5 km north of Leisey 1A.
Megalonyx is the most ubiquitous of the North American ground sloth
genera. The Irvingtonian species, M. wheatleyi did not range as widely as the
Rancholabrean M. jeffersonii, but is known from numerous localities in Florida
(McDonald 1977). Two of these, Inglis 1A, which is earlier than the Leisey IA
fauna, and the younger McLeod fauna, produced large numbers of individuals of
Megalonyx indicating that the genus was common in Florida. Megalonyx, in fact,
can be considered the most common ground sloth in Florida, having been found in
deposits ranging in age from late Hemphillian to late Rancholabrean. Like
Eremotherium, it is hypothesized to be a browser and an inhabitant of forests.
Although commonly found in deposits along rivers, unlike Eremotherium, it was
not restricted to gallery forests. Given its widespread distribution, its absence from
the Leisey IA fauna must reflect local ecological conditions which prevented it
from living close to the area of deposition. However, a few specimens of M.
wheatleyi are known from Leisey Shell Pit 3.
More is known of the ecology and food preferences of Nothrotheriops
shastensis, the descendent species of N. texanus than any other ground sloth,
except possibly Mylodon darwinii. The preserved dung balls of both N. shastensis
and M. darwinii have been collected and analyzed, although more so for
Nothrotheriops (Hansen 1978; Martin, Sabels and Shutler 1961). Cave deposits
preserving the dung of N. shastensis are chronologically and geographically
restricted to the late Rancholabrean of the Southwest, so caution must be exercised
in extrapolation from these data. Although the primary food resource was desert
shrubs (eg. Sphaeralcea, Ephedra, Atriplex and Acacia), N. shastensis was catholic
in its tastes and an opportunistic feeder (Hansen 1978). As pointed out by
McDonald (1985) the plant types in Florida available to Nothrotheriops are similar
enough to their western relatives that they were probably utilized by the genus.
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, No. 11
Nothrotheriops and Megalonyx in the late Pleistocene seem to be ecologically
incompatible. There are a few faunas in the western United States which contain
both genera, but there is a marked difference in the number of individuals of each
genus. At Rancho La Brea in Los Angeles, numerous individuals of
Nothrotheriops have been recovered but only parts of a single individual of
Megalonyx (Stock 1925). Likewise a similar pattern is seen in the fauna from San
Josecito Cave-numerous individuals of Nothrotheriops, but a single individual of
Megalonyx (Stock 1943). The only other locality in Florida at which
Nothrotheriops has been found, Pool Branch, did not include Megalonyx
(McDonald 1985). This generally consistent pattern of exclusion suggests that the
few localities where both genera have been recovered are probably near an ecotone
that provided a small area of overlap between their preferred habitats.
Paramylodon harlani is as common as Nothrotheriops in the Leisey IA fauna
(9 and 8 individuals respectively). Irvingtonian records of the species are rare, as
in the case of Nothrotheriops so it is difficult to evaluate the degree of overlap in
their habitat preference. Both are known from Rancho La Brea but P. harlani is
the more abundant. P. harlani is similarly abundant at American Falls Reservoir,
Idaho in which Megalonyx is also common but Nothrotheriops is absent. The
ecological requirements of P. harlani apparently were such that it could co-exist
with either Nothrotheriops or Megalonyx with equal probability. Stock (1925)
suggested that P. harlani was a grazer, and this interpretation has been followed by
most subsequent workers. It could also be argued that the powerful forelimbs, with
the expanded distal end of the humerus, short radius, ulna with an enlarged
olecranon process and dorsoventrally flattened unguals permitted Paramylodon to
dig up roots and tubers. Both interpretations permit us to view Paramylodon as
primarily an inhabitant of scrub or open country habitat.
BIOSTRATIGRAPHY
Compared to other North American ground sloth genera, Nothrotheriops
along with Eremotherium, was a relatively recent addition to the North American
fauna. The first ground sloth in North America is the megalonychid,
Pliometanastes, from the early Hemphillian (Late Miocene) (Hirschfeld and Webb
1968). Pliometanastes is replaced by Megalonyx in the late Hemphillian. The
mylodont lineage also first appears in the early Hemphillian and is represented by
the genus Thinobadistes (Webb 1989). A second invasion of mylodonts occurred
in the Blancan with the appearance of "Glossotherium" chapadmalense (Robertson
1976). It is presumed, but not yet demonstrated, that Paramylodon harlani is
derived from "G." chapadmalense and does not represent a third immigration of
mylodonts into North America.
Webb and Marshall (1982) recognized three phases to the Great American
Faunal Interchange, with the third phase subdivided into two parts. The first
368
MCDONALD: GRAVIGRADE XENARTHRANS FROM LEISEY SHELL PIT IA
rance of Nothrotheriops is considered to be indicative of Phase 3B, and Leisey 1A
appears to be the earliest fauna which includes Nothrotheriops. Eremotherium is
present in four Florida late Blancan sites (Morgan and Hulbert this volume) and
thus entered Florida much earlier. The slightly younger El Golfo fauna, State of
Sonora, Mexico is the earliest west coast record of Nothrotheriops. It is considered
to be early Irvingtonian in age (Shaw 1981). A supposed Blancan record of
Nothrotheriops (Golz, et al. 1974) has since been determined to be a
megalonychid, probably Megalonyx (Akersten and McDonald 1991).
BIOGEOGRAPHY
The wide coast to coast distribution of Nothrotheriops (Fig. 15) at the time of
its earliest appearance in North America suggests a fairly rapid dispersal and
integration into the North American fauna. This widespread distribution in the
Irvingtonian is in marked contrast to its range in the later Rancholabrean in which
it is confined to the western United States and northern Mexico (Akersten and
McDonald 1991). Assuming that the ecological requirements of Nothrotheriops
did not change during this time, the observed range reduction may represent the
animal's response to changes in available habitat. McDonald (1985) has already
suggested that its disappearance from Florida was due to the onset of more mesic
conditions in the early Rancholabrean. Whether this pattern holds in other parts of
its range can only be determined by the recovery of additional specimens with
associated pollen or flora.
Unlike Nothrotheriops, there does not appear to be an appreciable difference
in the Irvingtonian and Rancholabrean distribution of Paramylodon. During the
Irvingtonian, the northern edge of its range was at Rome, Oregon; Hay Springs,
Nebraska and Port Kennedy Cave, Pennsylvania. Northernmost records of
Paramylodon in the Rancholabrean include the Olympic Peninsula, Washington;
American Falls, Idaho; Tecumseh, Nebraska; and Big Bone Lick, Kentucky. Such
differences that do exist more likely reflect the relative paucity of Irvingtonian
faunas compared to those of the Rancholabrean.
McNab (1985) suggested that the northern expansion of Paramylodon was
facilitated by the combination of its large size and long hair. This permitted it to
tolerate climates with seasonally cool to cold periods. Another factor which may
have contributed to heat retention is its relatively short and compact limbs which
would have had a low ratio of surface area to volume. Nothrotheriops too was
covered with long hair but had a smaller body volume and its limbs were long and
slender. Studies of amino acid ratios in the bone indicate that Nothrotheriops had
a core body temperature lower than expected for an animal of its size (McNab
1985). Northernmost records of Nothrotheriops are from southern Oregon,
southern Utah, and Oklahoma. Comparison of Paramylodon to the similar sized
South American genus, Mylodon, by McNab showed that Mylodon and by
120013 18
014
011
A0 0
I I-I
200
Figure 15. Distribution ofNothrotheriops texanus andParamylodon harlani in the Irvingtonian. Symbols are: triangles = localities with onlyNothrotheriops
texanus, circles = localities with only Paramylodon harlani, squares = localities with both taxa. Numbers refer to the localities listed in Table 1.
MCDONALD: GRAVIGRADE XENARTHRANS FROM LEISEY SHELL PIT 1A
inference Paramylodon had a lower thermal conductance than Nothrotheriops,
thus permitting a greater tolerance to colder environments. As already noted, the
Blancan age "Glossotherium" chapadmalense, the probable ancestor to
Paramylodon harlani, is a much smaller animal, roughly half the size of the
Rancholabrean form. Although the number of faunas containing this species is
small, they all tend to be restricted to the southern United States (Arizona, Texas
and Florida). The northward expansion of the range of P. harlani during the
Irvingtonian may have been possible due to improved thermoregulation permitted
by the increase in body size, already discussed. The stability of Paramylodon's
distribution from the Irvingtonian to the Rancholabreait, in contrast to the
reduction of range of Nothrotheriops, may reflect this difference in thermal
sensitivity rather than being controlled by changes in habitat or food resources.
LITERATURE CITED
Akersten, W. A., and H. G. McDonald. 1991. Nothrotheriops from the Pleistocene of Oklahoma and
paleogeography of the genus. Southwest Nat 36(2):178-185.
Allen, G. M. 1913. AnewMylodon. Mem. Mus. Comp. Zool. 40(7):319-346.
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THE CINGULATES (XENARTHRA) OF THE
LEISEY SHELL PIT LOCAL FAUNA (IRVINGTONIAN),
HILLSBOROUGH COUNTY, FLORIDA
Kevin F. Downing' and Richard S. White2
ABSTRACT
The late early Irvingtonian Leisey Shell Pit local fauna provides a superb record of the diversity of
shelled edentates in the southeastern United States during the early Pleistocene. Among the four species of
cingulates recognized in the Leisey Shell Pit local fauna, two, the dasypodid, Dasypus bellus, and the
pampathere, Holmesina floridanus, are well represented in other Pleistocene fossil localities in Florida.
Fossil material ofD. bellus and H. floridanus, chiefly osteoderms at Leisey 1A, is indistinguishable from
comparable material at other Irvingtonian Florida localities except for modest differences in average size. A
third cingulate, a large glyptodont, is represented by a small sample of osteoderms, and is tentatively referred
to Glyptotherium arizonae.
The most notable cingulate in the Leisey Shell Pit local fauna is the thick-armored and relatively large
dasypodoid Pachyarmatherium leiseyi, here described as a new genus and species. P. leiseyi is presently
known from isolated osteoderms and postcranial elements, and from a nearly complete postcranial skeleton
in a private collection currently unavailable for detailed inspection. Large samples of Pachyarmatherium
leiseyi osteoderms have been recovered from Leisey 1A and Haile 16A, and several isolated postcranial
elements from Haile 16A. This new taxon is readily distinguished from other fossil and living armadillos by
characteristics of the carapace, including the thickness and morphology of the carapacial osteoderms, a
single, narrow transverse zone of imbrication between the pelvic and scapular bucklers and its unique border
and caudal osteoderms. It is distinguished from glyptodonts by its clawed ungual phalanges, free dorsal
vertebrae, and diminutive and probable edentulous jaws. The aggregate of skeletal morphology suggests that
P. leiseyi was a strong, non-fossorial scratch digger and may have been mymercophagus. Although the
detailed phylogenetic relationships of P. leiseyi are uncertain based upon limited available information, it
appears to retain many primitive features of cingulates in its postcranial skeleton and is most closely related
to the dasypodoid group. P. leiseyi first appeared in the late Blancan in North America, with records from
both Florida and South Carolina, and is best known from seven early Irvingtonian localities in peninsular
Florida.
1 The senior author is an Assistant Professor (Earth and Biological Sciences) at the School for New Learning, DePaul University, 243 S.
Wabash Avenue, Chicago IL 60604-2302, U S.A.
2 The junior author is a former student of the University of Arizona. Present address: 16606 North Columbus, Catalina, Arizona 85737,
U.S.A.
Downing, K. F., and R. S. White. 1995. The cingulates (Xenarthra) of the Leisey Shell Pit local fauna
(Irvingtonian), Hillsborough County, Florida. Bull. Florida Mus. Nat. Hist. 37 Pt. II(12):375-396.
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, No. 12
RESUME
La fauna local de fines del Irvingtoniano temprano, proveniente del Dep6sito de Conchuelas de
Leisey, provee un excelente registro de la diversidad de edentados con caparaz6n en el sureste de los Estados
Unidos durante el Pleistoceno temprano. De entire las cuatro species de cingulados reconocidas en la fauna
del Dep6sito de Conchuelas de Leisey, dos, el dasip6dido, Dasypus bellus, y el pampaterio, Holmesina
floridanus, estni bien representados en otras localidades de f6siles del Pleistoceno de Florida. El material
f6sil de D. bellus y de H. floridanus en Leisey lA consist principalmente de osteodermos, los cuales a part
de modestas diferencias en tamafio medio, son indistinguibles de material comparable proveniente de otras
localidades del Irvingtoniano de Florida. Un tercer cingulado, un gran gliptodonte esti representado por una
pequefa muestra de osteodemos, siendo referido tentativamente como Glyptotherium arlzonae.
El cingulado mis notable de la fauna local del Dep6sito de Conchuelas de Leisey, es un dasipodidoide
relativamente grande y de gruesa caparaz6n. Este cingulado, Pachyarmatherium leiseyi, represent un
nuevo g6nero y especie siendo conocido a trav6z de osteodennos aislados, elements postcraneales y un
esqueleto postcraneal casi complete perteneciente a una colecci6n privada actualmente no disponible para
una inspecci6n detallada. Se han recuperado grandes muestras de osteodernos de P. leiseyi de Leisey 1A y
Haile 16A, asi como various elements postcraneales aislados provenientes de Haile 16A. Esta nueva taxa se
distingue ficilmente de otros armadillos f6siles y vivientes en caracteristicas del caparaz6n, incluyendo su
grosor y morfologia de los osteodemos; una sola zona de imbricaci6n angosta y transversa entire los escudos
p6lvicos y escapulares; y lo singular de sus osteodennos caudales y del borde. Esta especie se distingue de
otros gliptodontes por la presencia de garras en las falanges unguales, por poseer vertebras dorsales libres y
mandibulas diminutas y probablemente edentadas. La morfologia esquel6tica complete sugiere que P.
leiseyi era de vida no subterrina, forido, cavador y probablemente minnec6fago. Aunque existed incerteza
acerca de las precisas relaciones filogen6ticas de P. leiseyi en base a lo limitado de la informaci6n
disponible, parecer ser que esta especie retiene varias caracteristicas primitivas de cingulados en el esqueleto
postcraneal relacionindose mis cercanamente al grupo dasip6dido. P. leiseyl apareci6 por primer vez en
Norte Am6rica en el Blancano tardio con registros en Florida y Carolina del Sur, siendo bien conocido desde
siete localidades del Irvingtoniano temprano en Florida peninsular.
INTRODUCTION
The three major groups of North American fossil cingulates, armadillos
(Dasypodidae), giant armadillos (Pampatheriidae) and glyptodonts
(Glyptodontidae), are represented in the late early Irvingtonian Leisey Shell Pit
local fauna. Dasypus belus is an average-sized armadillo with osteoderms that are
identical to other Florida Irvingtonian specimens described by Martin (1974).
Leisey IA specimens of D. bellus are distinguished from late Blancan ones
described by Robertson (1976) only by their slightly larger size. The
pampatheres, or giant armadillos, considered more closely related to the
glyptodonts and the eutatine armadillos than to the dasypodid armadillos by
Engleman (1985), are represented at Leisey 1A by Holmesina floridanus. The
specimens, which include a substantial number of non-carapacial elements, are
intermediates in the chronocline between the small Blancan H. floridanus and the
large Rancholabrean H. septentrionalis. The Leisey 1A sample is referred to
Holmesinafloridanus following Hulbert and Morgan (1993).
DOWNING & WHITE: CINGULATES OF LEISEY SHELL PIT
Pachyarmatherium leiseyi is a new dasypodoid comparable to the extant
armadillo genus Priodontes in size, but with thick osteoderms. P. leiseyi is
represented by isolated carapacial and caudal osteoderms at Leisey 1A and by
additional material from other sites in Florida and South Carolina, including a
nearly complete postcranial skeleton in a private collection. P. leiseyi appears to
have emigrated from South America to North America during the late Blancan
from a lineage of poorly known South American dasypodoids. Its temporal and
geographic distributions appear to have been restricted to the late Blancan and
early Irvingtonian of the southeastern United States, respectively (see Morgan and
Hulbert this volume for a discussion of the age of the Leisey and other Florida
Plio-Pleistocene faunas).
The glyptodonts at Leisey are represented by the large Glyptotherium
arizonae. The material referred to G. arizonae was not found in the principal
bone bed (Leisey 1A), but was limited to the stratigraphically lower shell bed in
the Leisey 1 quarry. Gillette and Ray (1981) presented a thorough discussion of
G. arizonae and the other species of Glyptotherium found in North America.
In the report below, we describe the cingulate material recovered from the
Leisey Shell Pit vertebrate localities, highlighting its relationship to similar
material from other fossil localities in Florida. In addition, for Pachyarmatherium
leiseyi, we incorporate information provided by a postcranial skeleton currently in
a private collection, which was displayed for sale at the 1992 Tucson Gem and
Mineral show. This specimen was collected at an undisclosed locality in Charlotte
County, Florida, in the late 1980s. Both authors briefly viewed this specimen at
the show and the junior author measured and photographed the reconstructed
animal.
ACKNOWLEDGEMENTS
The senior author wishes to thank S. David Webb and Gary S. Morgan of the Florida Museum
of Natural History and Richard C. Hulbert, Jr., of Georgia Southern University for their thoughtful
insights and reviews during the punctuated metamorphosis of this paper. Both authors wish to thank:
Everett Lindsay and Kevin Moodie, Department of Geosciences, University of Arizona, for
laboratory space and general consultation; Yar Petryzyn, Department of Evolutionary Biology and
Ecology, University of Arizona; Jay Villemarette and Henry Galiano for providing recent comparative
material; Gary S. Morgan, Florida Museum of Natural History, for arranging the loan of UF
specimens; John A. White, Department of Geosciences, University of Arizona, for a helpful
discussion on the use of material held in private collections; James Knight, South Carolina State
Museum, Columbia, South Carolina, for notification of the existence of South Carolina specimens of
Pachyarmatherium leiseyi. Downing examined the Leisey specimens and is responsible for the
descriptions of Dasypus bellus, Holnesina floridanus, and Glyptotherium arizonae, as well as the
diagnosis and description of P. leiseyi. White was principally responsible for recording and
integrating additional information from the privately held specimen of P. leiseyi. Both authors
collaborated in the development of the discussion section of P. leiseyi.
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, No. 12
SYSTEMATIC PALEONTOLOGY
Order XENARTHRA Cope 1889
Suborder CINGULATA llinger 1811
Superfamily DASYPODOIDEA Cabrera 1929
Pachyarmatherium new genus
Type and Only Known Species.-Pachyarmatherium leiseyi new species.
Chronologic and Geographic Ranges.-Late Blancan (late Pliocene) of
Florida and South Carolina; early Irvingtonian (latest Pliocene and early
Pleistocene) of Florida.
Diagnosis.-Interior carapacial osteoderms extremely small, thick; central
figure polygonal, convex with no medial depression, displaced towards one edge,
larger than peripheral figures; peripheral figures in single row, convex,
asymmetric pattern with largest figures opposite central figure, small or absent
along edge of displaced central figure, 3-6 in number; hair follicle pits at
intersection of groove around central figure and radial grooves, 1-4 in number;
surface smooth to weakly punctate; undersurface weakly concave, smooth to
weakly striated with several vascular foramina.
Etymology.--Pachyarma- in reference to the relatively thick osteoderm
armor; plus -therium for mammal.
Discussion.--Follows the description of P. leiseyi.
Pachyannatherium leiseyi new species
Type Specimens.-Holotype, UF 64347, interior carapacial osteoderm
collected by Mr. Frank A. Garcia 1983. Paratypes UF 81624, near border
carapacial osteoderm; UF 67099,80371, 81807, interior carapacial osteoderms
collected by personnel associated with the Florida Museum of Natural History
excavations conducted from 1983 to 1984.
Type Locality.-Leisey Shell Pit 1A, NW1/4, SE 1/4, SW 1/4 Sec. 15,
T32S, R18E, Ruskin 7.5' Quadrangle; Hillsborough County, Florida Bermont
Formation.
Chronologic and Geographic Ranges.-As for genus.
DOWNING & WHITE: CINGULATES OF LEISEY SHELL PIT
Referred Specmens.-Leisey Shell Pit 1A: UF 64396,67095-67099,
80036, 80037, 80220, 80316, 80317, 80508, 80532, 80615, 80687, 80767,
80892, 80893, 80916, 80959, 81004, 81288, 81622-81623, 81808, 81815,
82001, 82249-82250, 82336-82337, 82457, 82628, 82653-82655, 82770-82771,
82828-82829, 82924, 83103-83109, 83225, 83227, 83427-83428, 83585-83588,
83619-83620, 83679, 83767, 83826, 83856, 83975, 84076, 84291, 84478,
84762-84764, 84915, 84988, 85271-85274, 86163, 86183, 86197, 86327, 86348,
86361, 83674, 86385-86387, 86389, 86395, 86399-86404, 86417, 86432, 86440-
86445, 86450-86451, 86456, 86460-86461, 86472-86473, 86482-86485, 86488,
86491-86492, 86500, 86504, 86508-86509, 86513, 86523-86526, 86539-86543,
86665, 86686, 86836, 86854, 87188-87193, 87608, 87968-87972, 87978, 88083,
88151-88152, 88230-88233, 88366-88368, 88411, 88619, 88620, 88704,
132074-132084, 132900, 137649-137650, 142201-142202, 142226 osteoderms.
Leisey Shell Pit 3: UF 124174, 124175, 124555, 124556 four osteoderms.
Leisey Shell Pit 3A: UF 142208-142211, 142217 five osteoderms. Leisey Shell
Pit 3B: UF 132053, 133801 two osteoderms.
Additional Localities: Haile 16A, Alachua County: UF 95101-95188,
95196-95208, over 250 osteoderms; 135666, left metacarpal II (juvenile);
135667, left metatarsal H; 135668, right calcaneum. Port Charlotte, Charlotte
County: UF 10322, osteoderm. Payne Creek Mine, Polk County: UF 128986,
osteoderm; 61319-61322, four osteoderms (casts only). Apollo Beach,
Hillsborough County: UF 93001-93007, seven osteoderms. Kissimmee River 6,
Okeechobee County: UF 52673, 52675, two osteoderms. El Jobean Shell Pit,
Charlotte County: UF 131962, 131963, 131966, three osteoderms. Dorchester
County, South Carolina: several osteoderms.
Diagnosis.-As for genus.
Etymology.-leiseyi, for Mr. Bud Leisey, in recognition of his generous
support of the paleontological field work at the Leisey Shell Pit from 1983 to
1992.
Description.-Carapacial osteoderms small and relatively thicker than any
known dasypodid. In a sample of 42 osteoderms from Leisey 1A, mean greatest
width is 13.8 mm with an observed range of 8.1-22.9 mm, while mean thickness
is 8.9 mm with an observed range of 5.5-13.3 mm. The osteoderms are
structurally similar to those of glyptodonts, however, they are approximately one
third the width and half the thickness of those from Glyptotherium arizonae and
G. floridanum.
Figures on the smooth to weakly punctate external surface of the osteoderms
are well preserved and separated by distinct grooves. The arrangement of the
figures is similar to that in Glyptatelus and Dasypus bellus in that the central
figure is displaced towards one edge of the scute; it differs from D. bellus in that
379
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, No. 12
the peripheral figures are more regular and well defined by the greater groove
depth (Fig. 1A). Central figures are approximately one half the osteoderm width,
and all those studied were distinctly convex with no medial depressions. The
sides of the central figure generally parallel the sides of the less regularly shaped
peripheral figures, giving it an overall polygonal appearance. Convex peripheral
figures typically number 4 or 5 (observed range: 3 to 6), similar to the condition
observed in D bellus.
The number and location of hair follicle pits on Pachyarmatherium leiseyi
are similar to those of dasypodids. Deep pits are located where the groove around
the central figure intersects with the radial grooves between peripheral figures.
These pits number from one to four, one being the most common. The pits are
typically situated at the intersection nearest the largest peripheral figure.
The undersurfaces of the osteoderms show a smooth to weakly striated
texture on a slightly concave surface (Fig. 1B). Typically, the undersurface is
marked by several small foramina. In side view, the osteoderms reveal their
trabecular internal microstructure (Fig. 1C).
A near border osteoderm is represented by UF 81624 (Fig. 1D). It is
pentagonal in shape with a moderately conical surface showing little punctation
and resembles the bossed posterior border osteoderms of the glyptodont G.
floridanum. All of its sides appear to have had adjacent osteoderms. It is similar
in size to average interior osteoderms. Additional Pachyarmatherium leiseyi
osteoderms that have been found in other Florida localities, and Dorchester
County in South Carolina, show no major differences from those at Leisey 1A.
A large number of osteoderms (>250) from Haile 16A, which had been
curated as G. floridanum (as juveniles), are here assigned to P. leiseyi. These
specimens, including some juvenile osteoderms, provide a great deal of additional
information about P. leiseyi armor. The interior carapacial osteoderms from Haile
16A (Figs. 2A, B) are very similar in character to the Leisey 1A osteoderms,
having typically 3 to 5 peripheral figures (observed range 2 to 6) and 1 or 2 hair
follicle pits (observed range 0 to 3). In 65 specimens (UF 95101-95165), mean
width is 13.6 mm with an observed range of 9.6-18.1 mm, while mean thickness
is 7.4 mm with an observed range of 5.0-11.2 mm. This suggests that the Haile
specimens are nearly identical to the Leisey 1A specimens in width but slightly
thinner. The juvenile interior carapacial osteoderms (Fig. 2C) generally average
fewer peripheral figures (typically 3) than the adults. There is usually a single
hair follicle pit and, whereas the central figure in the adults was approximately
one half the osteoderm width, the central figure in juveniles is even more
prominent, approximatley two thirds the osteoderm width.
A variation on the normal interior carapacial osteoderm is seen in the Haile
16A specimens UF 95166-95169. The specimens have thicknesses almost as great
as their widths and also have convex bottoms. They show one hair follicle pit,
two peripheral figures, and a unique central figure which extends beyond the side
of the osteoderm forming an overhang.
DOWNING & WHITE: CINGULATES OF LEISEY SHELL PIT
A B
C D
Figure 1. Pachyarmatherium leiseyi from Leisey lA. Carapacial osteodenn holotypee, UF 64347). (A)
dorsal surface; (B) undersurface; (C) side; (D) near border osteoderm (paratype, UF 81624) dorsal surface.
Scale bar 10 mm in length.
Two different types of Pachyarmatherium leiseyi border osteoderms have
been identified from Haile 16A. The first group (UF 95177-95183) is relatively
large compared to the interior osteoderms. They have from one to two hair
follicle pits, two well defined peripheral figures (some have a very small third
figure), and in lateral view their rounded sides can be seen (Figs. 2D, E). On the
surface of this rounded side there is typically a small furrow. A distinctive small
projection juts out near the bottom of the side which abuts more interior
osteoderms and presumably helps adjoin them. A juvenile example of this border
osteoderm shows few differences from the adult specimens (Fig. 2F).
The second group of border osteoderms are represented by Haile 16A
specimens UF 95170-95175, and are characterized by relatively thin wedge-like
lateral profiles, two hair follicle pits, three peripheral figures, and a central figure
that tends to be large and pentagonal (Figs. 2G, H). A juvenile specimen closely
resembles the adult form (Fig. 2). This group of border osteoderms is most likely
from the anterior edge of the pelvic buckler.
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, No. 12
D
G~.
J
B
P-
E
H
C
F
* .<*
K
y'-- m
Figure 2. Osteodenns ofPachyarmatherium leiseyi from Haile 16A (Irvingtonian). Interior carapacial (UF
95102): (A) dorsal view, (B) lateral view. Juvenile (UF 95200); (C) dorsal view). Carapacial border (UF
95177); (D) dorsal view;, (E) lateral view. Juvenile (UF 95183); (F) dorsal view. Carapacial border (UF
95172); (G) dorsal view, (H) lateral view. Juvenile (UF 95176); (I) dorsal view. Caudal osteodern (UF
95185); (J) dorsal view; (K) lateral view. Scale bar 10 mm in length.
A final type of osteoderm from Haile 16A (UF 95184-95188) is very different
from the others. It is characterized by having no central or peripheral figures, a
single hair follicle centrally positioned over the thickest edge, and smooth curved
surfaces (Figs. 2J, K). The underside of the osteoderm is curved convexly along
the length. This osteoderm form most likely represents part of the caudal armor.
Three postcranial elements from Haile 16A are tentatively referred to
Pachyarmatherium leiseyi: a juvenile left metacarpal II, a left calcaneum (Fig. 3A),
a left metatarsal II (Fig 3E). Justification for referring these elements to P. leiseyi
are presented in the discussion below.
DOWNING & WHITE: CINGULATES OF LEISEY SHELL PIT
AC
SE
FF
> .17 t
.'' ,' ^ *
Figure 3. Comparison of Pachyarmatherium leiseyi and Dasypus bellus postcranial elements from Haile
16A. (A) dorsal, and (C) medial views of right calcaneum ofP. leisey, (UF 135668). (B) dorsal, and (D)
medial views of right calcaneum of D. bellus (UF 24938). Anterior views of left metatarsal IIs of (E) P.
leisey, (UF 135667) and (F)D. bellus (UF 135645). Scale bar 10 mm in length.
Discussion.--When osteoderms of Pachyarmatherium leiseyi were first
examined, they were initially allocated to the Glyptodontidae because of several
shared characteristics (e.g., extreme thickness and lack of movable osteoderms).
This was the draft interpretation when Webb et al. (1989:105) mentioned this
taxon in their discussion of the Leisey site geochronology as "a new, small kind of
glyptodont". Hulbert and Morgan (1989) also referred to this species as a
miniature glyptodont, probably a new species. In February, 1992, the authors
examined a nearly complete, but poorly restored, postcranial skeleton with
associated carapace in a private collection on display for sale at the Tucson Gem
and Mineral Show. This skeleton provided additional information concerning the
morphology of this new dasypodoid. Discussions with G. Morgan (personal
communications, 1992) indicated that he and R. Hulbert had also seen and
recognized the affinity of this specimen to previously collected material, as it has
been offered up for sale in Florida before its display in Tucson and current
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, No. 12
restoration. While the type description and diagnosis sections above have been
based upon specimens available in museum collections, we have chosen to use the
observations made upon the privately held specimen in the discussion which
follows. A much more detailed description and analysis needs to be made of this
material if and when it becomes available for examination. Table 1 summarizes
our preliminary measurements on the postcranial skeleton. It should be
emphasized here that the measurements were made on a poorly restored and
mounted specimen under less than ideal conditions. Measurements were only
taken on elements which had not been restored. We believe them to be accurate
enough to provide a good indication as to the size of the various elements listed.
Armor: One of the most distinguishing characteristics of Pachyarmatheriwn
leiseyi is its carapace. As has already been noted, the osteoderms are extremely
thick relative to their small size. The sutures between adjoining osteoderms
consist of strongly intermeshing trabecular structures similar to the thick
glyptodont carapacial osteoderms (Fig. 4). The associated carapace of the
privately-held specimen reveals additional information regarding the dermal armor
of P. leiseyi. Most notably, its carapace consisted of an anterior scapular buckler
and a posterior pelvic buckler whose common border formed a restricted
transverse area of imbrication. The anterior buckler overlapped the posterior
buckler along a single band of osteoderms with one wedged shaped edge, likely
permitting modest flexure of the carapace. Unlike the bands of many dasypodids,
which permit both anterior and posterior imbrication and motion between bands of
moveable osteoderms, the two respective osteoderm bands involved with the
medial carapacial break were tightly integrated and sutured to the rest of the
carapace along their remaining four sides (i.e., they were immovable).
Not a single osteoderm analogous to the independently movable bands of
pampatheres or dasypodids were recovered with this specimen, while many
hundreds of osteoderms (representing approximately 75% of the carapace),
including nearly all the edges of the two fixed bucklers, were recovered. While it
is possible that all of the movable osteoderms had become disassociated from the
specimen during its original burial and/or recovery, the fact that the two fixed
portions overlap precisely and that the length of the carapace thus overlapped
matches the remainder of the post-cranial skeleton so well, argues for the
interpretation that we have proposed here.
Among the recent dasypodids, the number of movable bands in the carapace
ranges from a minimum of one (rarely) in Tolypeutes to as many as 14 in
Priodontes (Wetzel, 1985). In Stegotherium, a well described pre-Pleistocene
armadillo allocated to the Dasypodini by Engleman (1985), the carapace consists
of an uncertain number (but at least 20) of movable bands, which are not so
clearly differentiated from the immovable osteoderms. In fact, Scott (1903a) was
not certain whether any of the pelvic buckler osteoderms were fixed in
Stegotherium; he does state that a fixed scapular buckler is not present. The
DOWNING & WHITE: CINGULATES OF LEISEY SHELL PIT
Table 1. Measurments (in mm) ofpostcrania ofPachyarmatherium leisey, based on measurements of
mounted skeleton in private collection except where indicated.
height
height of spine
length
distal width
total length
length ofolecranon process
length of remainder of ulna
distal width
length
distal width
width through trochanter and head
height
width
length
distal width
length
length (UF135668)
120.00
36.5
67.0
23.0
115.0
57.0
58.0
29.0
150.0
42.0
53.5
30.0
17.0
99.5
45.0
56.0
55.0
B
Figure 4. Comparison of interior carapacial osteoderms. (A) Glyptotherium floridanum; (B)
Pachyarmatherium leiseyi. (X 1.00).
structural character of the single area of imbrication on P. leiseyi is suggestive of a
morphological condition incipient to the development of multiple bands, however,
the apparent variability of band numbers in modem forms leaves this hypothesis
Scapula:
Radius:
Ulna:
Femur:
Patella:
Tibia:
Calcaneum:
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 37, PT. IL No. 12
equivocal until a broader phylogenetic analysis of cingulates can establish more
clearly the patterns and polarity of movable band addition or reduction.
The caudal armor of P. leiseyi consists of a series of eight tubes each
underlain by a single caudal vertebra. Each tube consists of three rows of
osteoderms, the posterior most of which are slightly flared outward and which
tend to be pointed, producing a weakly serrate posterior margin. The terminal
caudal cone's anterior row of osteoderms is smaller in diameter than the
immediately preceding tail section. The cone shows no trace of terminal
enlargement. The individual osteoderms of the tail sections do not show a rosette
pattern with a central figure as in the carapacial elements. Each has a low border
rising to a keel which is oriented from the anterior to the posterior end of the
osteoderm.
Postcrania: Several general observations can be made about the remainder
of the skeleton. The thoracic and lumbar vertebrae are all free, not fused or co-
ossified in the dorsal tube and synsacrum as observed in glyptodonts. The digits
of both the manus and pes in Pachyarmatherium have strong digging claws, all of
which are approximately equal in size. There is none of the enlargement of the
central digits seen in some of the dasypodids, such as the comparably giant
Priodontes. The ungual phalanges are not hoof-like, unlike those of
glyptodontids, including early forms such as those in the Propalaehoplophorinae
group. The ungual phalanges of the manus are slightly narrower and more claw-
like than those of the pes.
One of the most exceptional characters of the postcranial skeleton is in the
structure of the ulna. In this specimen, the length of the olecranon process to the
remainder of the ulna is 57 mm to 58 mm (98%), a higher proportion than that
recorded for any other fossorial mammal by Hildebrand (1985). The closest
extant cingulate with similar proportions, cited by Hildebrand, is Euphractus, a
dasypodid armadillo with an olecranon process 95% the length of the remainder of
the ulna. While the extreme development of the olecranon process is typically
correlated with a digging adaptation, Pachyarmatherium shows few of the
correlated modifications usually accompanying such development. Neither
adaptations for humeral rotation digging nor the extreme development of hooking
and pulling digits such as that found in the anteaters or in the dasypodid
Priodontes are present. Pachyarmatherium may have been a more generalized
scratch digger, similar to Dasypus novemcinctus.
Three postcranial elements from Haile 16A represent a small cingulate and
are referred to Pachyarmatherium. They are similar in size, but differ in
morphology from Dasypus bellus, the only other small cingulate in the fauna.
They also resemble the corresponding elements of the privately held specimen. A
left calcaneum (UF 135668) is nearly the same length as a calcaneum of D. bellus
(UF 135649), yet differs in the nature of the articular surfaces, particularly the
sustentacular facet (Fig. 3A, B). The calcaneum of P. leiseyi is also slightly less
robust. A left metacarpal II (UF 135666) is from a juvenile individual as
DOWNING & WHITE: CINGULATES OF LEISEY SHELL PIT
evidenced by the missing and unfused distal epiphysis. It is shorter and wider
than the corresponding element in D. bellus (UF 135643). The proximal end of
this element is more pronounced ventrally as a massive knob dissimilar to the
condition observed in D. bellus. The prominence located on the dorsoexternal
border at midshaft for attachment of the extensor carpi radialis is smaller than that
of D. bellus, although the extent that this is due to the immaturity of the specimen
at hand is unknown. A left metatarsal H (UF 135667) is similar in size and gross
morphology to the same element in D. bellus (UF 135645), but is considerably
shorter and therefore relatively more robust (Figs. 3E, F). The proximal
articulation is narrower and is longer dorsoventrally. The median tubercle on the
distal (phalangeal) articulation is not as strongly developed as is that of D. bellus
(UF 135646), and the two halves of the distal articulation located on either side of
the median tubercle lie in the same plane, whereas in D. bellus the external side is
inclined relative to the internal side.
Skull: A few fragments of a skull were found along with the postcranial
material of the privately held specimen. In so far as we have been able to
ascertain, there was no other cingulate material obtained at the locality other than
this individual. Therefore we consider it likely that these cranial and jaw
fragments are indeed from P. leiseyi. One fragment consisted of the parietals and
frontals including the dorsal margin of one orbit. The skull fragments indicate a
lunate occipital crest comparable to those of Dasypus novemcinctus. More
significantly, however, are three consequential fragments of the lower jaw. Two
fragments are from the left mandible, and while not actually fitting together, are
estimated to lack only about 5 mm or less between them. Other than the one small
missing intervening portion, that side of the lower jaw is complete. The third
fragment represents the anterior end of the right jaw.
The lower jaws appear to have been diminutive like those of Stegotherium
tesselatum, from the early Miocene of South America, rendered in Scott (1903A).
They were probably edentulous, unless the missing portion contained alveoli for
very small teeth. However, the ramus of the mandible just adjacent to the missing
portion on both sides is thin and blade-like with no trace of a swelling to
accommodate alveoli. The mandibular symphysis appears to have been reduced
with no evidence of a strong suture between the mandibular rami. In this respect,
the mandible matches the condition seen in Dasypus novemcinctus. As observed
in the dasypodids, there appears to be two mental foramina in each jaw, with the
posteriormost being the larger. The coronoid process extends much above the
mandibular condyle which in turn is not elevated above the horizontal ramus.
This character also agrees with species of Dasypus. If the skull material is
correctly associated with the remainder of the postcranial skeleton, then
Pachyarmatherium may have been a more functionally committed myrmecophage
than is Dasypus, but possibly less so than the anteaters (Myrmecophaga and
Tamandua) or the pangolins (Manis). These latter groups are also edentulous and
show a reduction of the horizontal ramus, but have a much greater reduction of the
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, No. 12
ascending ramus indicating even more pronounced reduction of the masticatory
system.
Phylogenetic Relationships.-It is evident that P. leiseyi shows a
combination of features associated with armadillos and glyptodonts. The almost
entirely rigid carapace, comprised of thick and sutured osteoderms with deep
grooves as well as highly bossed caudal and border ornamentation, is structurally
analogous to features usually associated with glyptodonts. On the other hand,
osteoderm imbrication permitting flexure of the pelvic and scapular bucklers is a
characteristic usually associated with armadillos and giant armadillos. It should be
noted, however, that a simple imbricating band near the middle of the length of
the carapace, as is observed for P. leiseyi, may also have been present, at least in
part, in some early glyptodont groups. For example, Scott (1903b) and
Hoffstetter (1958) indicate that some primitive glyptodonts, such as those of the
subfamily Propalaeohoplophorinae of South America, appear to have had an area
of imbricating osteoderms near their lateral margin. The figure ornamentation
patterns of P. leiseyi carapacial osteoderms are similar in their peripheral figure
reduction and central figure displacement to those seen on armadillos such as
Dasypus and the glyptateline glyptodonts such as Glyptatelus tatusinus figured in
Hoffstetter (1958). Unlike Glyptatelus, P. leiseyi central figures are polygonal
and have hair follicle locations restricted to groove intersections.
The presence of claws rather than hooves and free dorsal vertebrae in P.
leiseyi, may be retained primitive features of cingulates seen in other dasypodoids.
The diminutive and possibly edentulous partial jaw associated with the P. leiseyi
skeleton, is suggestive of a derived grade seen in other dasypodids, such as those
of the subfamily Stegotheriinae from the Miocene of South America. Early
glyptodonts, including members of the Propalaeohoplophorinae and the
Glyptatelinae do not show dentary reduction. The character of the jaw, in
combination with the other skeletal features, argues for the provisional assignment
of this genus to the dasypodoid group. Under this hypothesis, the thickening of
the osteoderms observed for P. leiseyi may have been derived separately from that
of the glyptodontids.
We have refrained from presenting a more detailed phylogenetic analysis,
including familial assignment, because of the limited examination of the private
specimen and because many critical characters are not preserved. For instance,
the skull characters used by Engleman (1985) in his general analysis of the
cingulates, such as an ossified bulla, are not available even on the exceptional
private specimen. Until the postcranial material mentioned above becomes
available, or until other material is discovered, a more rigorous phylogenetic
analysis of this pivotal cingulate will not be possible.
DOWNING & WHITE: CINGULATES OF LEISEY SHELL PIT
Family DASYPODIDAE Bonaparte 1838
Dasypus bellus (Simpson 1929)
Referred Specimens.-Leisey Shell Pit 1A: UF 64341, 80173, 80560,
80686, 81813, 81814, 81927, 83223, 83224, 83425, 83426, 85332, 83584,
83837, 84852, 86326, 86423, 86439, 86446, 86471, 86664, 87186, 87187,
88702, 132085, 132086, 142203, 142204 immoveable osteoderms; UF
80003,80891, 81402, 83134, 86388, moveable osteoderms; UF 115730, right
tibiofibula. Leisey Shell Pit 3: UF 130011 movable osteoderm. Leisey Shell Pit
3A: UF 142205-142207, 142216, 142220 immovable osteoderms. Leisey Shell
Pit 3B: UF 132046 right distal femur.
Discussion.-Darypus bellus is represented by both moveable and
immoveable osteoderms at Leisey Shell Pit. The immoveable osteoderms are
roughly hexagonal with large, weakly convex central figures. The central figures
are situated towards one edge of the osteoderms and are bordered by 2-6
irregularly shaped peripheral figures. There are typically 3-4 hair follicle pits
situated within the groove that surrounds the central figure, some of which are
situated at the intersection of the radial grooves between peripheral figures and the
groove that surrounds the central figure. Osteoderm undersides are typically
marked by a small central foramen. The moveable imbricatingg) osteoderms are
rectangular, with convergent rows of hair follicle pits ornamenting the wedge-
shaped posterior end.
Osteoderms of Dasypus bellus from Leisey do not differ significantly in
appearance from those found in the Florida Blancan sites of Haile 15A and Santa
Fe River 1B nor from osteoderms at Irvingtonian sites such as Inglis 1A, Haile
16A, and Coleman 2A. Leisey 1A immoveable osteoderm sizes overlap with
those from Blancan and early Irvingtonian sites (Table 2). There are few well
preserved moveable osteoderms from Leisey 1A, so that little can be concluded
about their sizes.
Although the size ranges of the immoveable osteoderms have substantial
overlap, the mean values produce a trend towards increasing size for Dasypus
bellus from the Blancan through the Irvingtonian. This is in agreement with the
size increase noted by Martin (1974) for moveable osteoderms. With such a small
sample of osteoderms, however, (relative to the hundreds, which vary in size, on
an individual carapace), support for a general chronocline increase in size through
time, as recorded by osteoderms, is far from conclusive.
Family PAMPATHERIIDAE Paula Couto 1954
Holmesinafloridanus (Robertson 1976)
Referred Specimens.--Leisey Shell Pit 1A: UF 120951, right mandible
with four teeth (numbers 5-8); 65890, 86419, 86685, isolated upper 4th, 9th, and
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, No. 12
9th teeth, respectively; 67100, maxillary fragment; 67500, partial basicranium
(collected away from the main bone bed); 84749, femur; 86488, juvenile femur;
86538, tibiofibula; 65900, juvenile tibia; 83226, astragalus; 86124, metatarsal IV;
86487, metatarsal II; 813636, digit IV ungual phalanx; 86351, partial scapula;
86638, humerus; 85622, partial ulna; 86470, juvenile radius; over 350 isolated
osteoderms including 64342-64345, 80888, 80915, 81002, 86411, and 86431.
Leisey Shell Pit 1: UF 66422, right mandible with 5th and 9th teeth.
Table 2. Measunnents (in mm) ofimmoveable osteoderms ofDasypus bellus from the late Pliocene and
early Pleistocene of Florida. N = number of specimens; OR = observed range.
Thickness Maximum Width
N Mean OR Mean OR
Blancan
Haile 15A
(UF 24976) 10 3.8 3.5-4.5 9.7 8.3-12.4
Very Early Irvingtonian
Inglis IA
(UF 24978) 10 4.1 3.6-4.7 11.6 8.4-14.5
Early Late Irvingtonian
Leisey 1A 8 4.6 3.2-5.5 13.0 11.2-14.9
Discussion.--A general trend in pampathere evolution towards increasing size
has been well documented and discussed in the literature (Robertson 1976; Kurt6n
and Anderson 1980; Edmund 1985a, 1985b, 1987; Hulbert and Morgan 1993).
The fossils from Leisey 1A agree with this trend and differ predominantly only in
size from Blancan and Rancholabrean specimens. Robertson (1976) established
that the small Blancan Holmesinafloridanus (which he described as Kraglievichia
floridanus) is directly ancestral to the large Rancholabrean H. septentrionalis,
forming a chronocline. Edmund (1987) quantified this trend in size on the basis
of additional material, and placed K. floridanus in Holmesina. The Leisey 1A
material is assigned to H. floridanus following Hulbert and Morgan (1993), who
demonstrated that the Florida Blancan species is H. floridanus, the middle to late
Irvingtonian and Rancholabrean species is H. septentrionalis, and that early
Irvingtonian specimens are intermediate between the two in size but referable to
H. floridanus.
The partial right mandible, UF 66422, contains the 5th and 9th teeth, and
alveoli for all but the first tooth. The two teeth differ only in size from other
Holmesina floridanus specimens. UF 66422 is slightly larger than a right
390
DOWNING & WHITE: CINGULATES OF LEISEY SHELL PIT
Table 3. Measurements (in mm) of mandibles ofHolmesinafloridanus from Leisey Shell Pit and Inglis IA.
Characters Leisey IA Leisey IA Inglis IA
UF 66422 UF 129051 20948
Alveolar measurements
tooth 3: length 10.6 9.4
width 6.7 6.4
tooth 4: length 13.0 11.6 13.0
width 7.0 7.7 6.3
tooth 5: length 17.6 18.6 15.1
width 9.8 9.9 -
tooth 6: length 17.8 22.4 18.5
width 11.5 11.8 9.2
tooth 7: length 16.8 22.5 17.7
width 10.0 10.9 9.5
tooth 8: length 14.8 17.1
width 9.6 8.2
tooth 9: length 11.0 12.9
width 7.3 7.0
Mandible thickness at
7th alveolus 20.5 19.9 19.2
Table 4. Cranial measurements ofHolmesinafloridanus from Leisey Shell Pit.
Anteroposterior length tooth 4 (UF 65890) 13.8
Anteroposterior length tooth 9 (UF 86419) 11.7
Anteroposterior length tooth 9 (UF 86685) 11.4
Partial braincase (UF 67500)
Transverse diameter between hypoglossal foramina 45.0
Transverse diameter between foramina ovale 46.7
Length ofbasioccipital from ventral edge of foramen
magnum to basioccipital-basisphenoid suture 51.7
Transverse diameter, right facet for occipital
condyle 21.9
Transverse inside diameter, occipital condyle 34.0
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, No. 12
mandible, UF 20948, found at Inglis 1A, early Irvingtonian (Table 3), and also
differs from the Inglis specimen in having two large mental foramina located
centrally beneath the second alveolus with a third small foramen located more
posteroventrally. UF 20948 has a linear arrangement of all three foramina with
the two most anterior foramina beneath the 3rd tooth. Additionally, the
masseteric fossa is more restricted on UF 66422.
A second mandible from Leisey, UF 129051, has teeth 5 through 8, but does
not preserve as much of the ramus as does UF 66422. The shape of the teeth is
similar to the other Leisey mandible and the Inglis jaw, but the measurements of
the teeth, especially length, are larger (Table 3).
A basicranium, UF 67500, consists of a large basioccipital and an incomplete
auditory bulla with the right condyle and the right squamosal portion of the
zygomatic arch preserved (measurements in Table 4). It resembles a more
complete skull of Holmesina septentrionalis from the Pleistocene of Texas
described by James (1957). An isolated upper left 4th tooth, UF 65890 from
Leisey 1A, has a reniform occlusal outline. Unlike late Pleistocene specimens,
there is an additional concave surface running down the posterior lobe of this
tooth. Lastly, a left maxillary fragment, UF 67100, with portions of the 6th and
7th alveoli is slightly more robust than similar Inglis 1A fragments.
Among the elements representing the limbs are a tibiofibula, UF 86535, a
juvenile tibia, UF 65900, and a digit IV ungual phalanx, UF 81363. Features of
the tibiae agree with those of a large Holmesina from the latest Pleistocene at
Hornsby Springs (UF 4016). Other than its smaller size, the ungual phalanx
shows little difference from a specimen (UF 9336), from Branford 1A
(Rancholabrean). The humerus from Leisey 1A, UF 86638, exhibits the typical
intermediate size relationship with Blancan and Rancholabrean specimens (Fig 5;
Table 5). A Leisey metatarsal IV (UF 86124) has a length of 37.3 mm. A single
Blancan example measures 28 mm, Irvingtonian examples average 39 mm, and
Rancholabrean examples diminish to an average of 30 mm. (Edmund, 1987). The
Leisey example, late early Irvingtonian, fits well within the demonstrated
chronocline.
The relative size of moveable and immoveable osteoderms of Holmesina is a
reasonably good biostratigraphic indicator for Florida Blancan, Irvingtonian, and
Rancholabrean sites (Edmund 1985b; Hulbert and Morgan 1993). The Leisey 1A
osteoderms fall between Blancan and Rancholabrean specimens and are slightly
smaller (Fig. 6) than those at Inglis 1A (earliest Irvingtonian) or Haile 16A (late
early Irvingtonian). In a sample size of 19, the average length of moveable
osteoderms from Leisey lA was found to be 78.2 mm with an observed range of
61.5-92.7 mm, while the average width was determined to be 26.4 mm with an
observed range of 22.8-29.1 mm. Since there are more than 600 osteoderms on
the carapace of Holmesina (Edmund 1985b), caution should be employed, as with
Dasypus bellus osteoderms, when generalizing about evolutionary and
DOWNING & WHITE: CINGULATES OF LEISEY SHELL PIT
B
r&.
Figure 5. Comparison ofHolmesina right humeri, anterior view. (A) H. floridanus, Santa Fe 1, Blancan
(UF 10432); (B) Holmesinafloridanus, Leisey IA, Irvingtonian (UF 86638); (C) H. septentrionalis,
Coleman 3B, Rancholabrean (UF 15140). Scale bar 40 mm in length.
Table 5. Postcranial measurements ofHolmesinafloridanus from Leisey Shell Pit
Femur (UF 84749) length 225.0
width at 3rd trochanter 42.3
diameter of head 24.3
Scapula (UF 86351) transverse diameter glenoid facet 22.9
Humerus (UF 86638) length 175.0
Ulna (UF 85622) width at semi-lunar notch 29.5
Tibiofibula (UF 86538) diameter of opening 108.0
Astragalus (UF 83226) length 37.7
MT II (UF 86487) length 41.4
MT IV (UF 86124) length 37.3
Ungual phalanx digit IV
(UF 81363) length 28.6
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II No. 12
biostratigraphic placement from small samples of osteoderms alone. Hulbert and
Morgan (1993), subsequent to the measurements discussed here, have analyzed a
greater sample of the Leisey Holmesina.
Family GLYPTODONTIDAE Burmeister 1879
Subfamily GLYPTODONTINAE Trouessart 1898
Glyptotherium arizonae Gidley 1926
Referred Specimens.--Leisey Shell Pit 1: UF 124618-124630, 13
osteoderms, possibly from a single individual; 131976, interior carapacial
osteoderm.
Description.-A poorly preserved osteoderm (UF 131976) is from the
interior of the carapace and is marked by eight peripheral figures, a large central
figure, and several hair follicle pits. The series UF 124618-124630 contains four
typical interior carapacial osteoderms (124618-124621) with the diagnostic
morphology of G. arizonae. The size and morphology of these osteoderms
matches those from Florida referred to G. arizonae by Gillette and Ray (1981).
G. arizonae is limited to the lower shell bed of Leisey 1 and is not found in the
Leisey 1A horizon.
A L S.2
3 a.-.
Figure 6. Comparison ofHolmesina movable osteoderms. (A) Santa Fe 1, Blancan (UF 10431); (B) H.
floridanus, Haile 15A, Blancan (UF 10902); (C) H. floridapus, Inglis IA, Irvingtonian; (D) Holmesina
floridanus, Leisey IA, Irvingtonian (UF 86498); (E)H. septentrionalis, Branford IA, Rancholabrean (UF
9336). Scale bar 30 mm in length.
DOWNING & WHITE: CINGULATES OF LEISEY SHELL PIT
SUMMARY
It has been recognized for decades that edentates were an important
component of the Pleistocene faunas of Florida (e.g., Holmes and Simpson,
1931). The Leisey Shell Pit 1A local fauna provides a superb record of the
diversity of the cingulate edentates in the southeastern United States during the
late early Irvingtonian. The relatively high number of cingulates at this time,
arguably their peak diversity interval in this region, developed as new immigrants
from South and Central America ventured across the improved intercontinental
connections during the Pleistocene Epoch. Among the four species of shelled
xenarthrans recognized in the Leisey Shell Pit 1A local fauna, Dasypus bellus and
Holmesinafloridanus are very well known from other localities in Florida. The
distribution of Glyptotherium arizonae included the Gulf Coast and southwestern
United States.
The most notable cingulate in the Leisey Shell Pit local fauna is
Pachyarmatherium leiseyi. P. leiseyi is presently known from isolated osteoderms
and postcranial elements, and from a nearly complete postcranial skeleton in a
private collection currently unavailable for detailed inspection. This new
dasypodoid is readily distinguished from fossil and living armadillos by
characteristics of the carapace, including its thick osteoderms, a single area of
imbrication between the pelvic and scapular bucklers, unique border and caudal
osteoderms, and edentulous jaws. Among the many features which distinguish it
from the Pleistocene glyptodonts are its much smaller size, osteoderm
morphology, free dorsal vertebrae, and presence of claws rather than hooves. The
known skeletal morphology suggests that P. leiseyi was functionally a strong
scratch digger. P. leiseyi has not been found in significantly younger localities
than Leisey in the southeastern United States, therefore, it may have had a
relatively brief presence in North America after its dispersal from South America
in the late Pliocene.
LITERATURE CITED
Edmund, A. G. 1985a. The fossil giant armadillos of North America (Pampatheriinae,
Xenarthra=Edentata). Pp. 83-93 in G. G. Montgomery, ed. The evolution and ecology of
armadillos, sloths, and vermilinguas. Smithsonian Inst. Press, Washington, D.C.
1985b. The armor of fossil giant armadillos. Texas Mem. Mus. Pearce-Sellards Ser. 40:
1-21.
1987. Evolution of the genus Holmesina (Pampatheriidae, Mammalia). Texas Mem.
Mus. Pearce-Sellards Ser. 45:1-20.
Engleman, G. F. 1985. The phylogeny of the Xenarthra. Pp. 51-64 in G. G. Montgomery, ed.
The evolution and ecology of armadillos, sloths, and vermilinguas. Smithsonian Inst. Press,
Washington, D.C.
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, No. 12
Gillette, D. G., and C. E. Ray. 1981. Glyptodonts of North America. Smithsonian Contrib.
Paleobiol. 40:1-255.
Hildebrand, M. 1985. Digging of quadrupeds. Pp. 89-109 in M. Hildebrand, D. Bramble, K.
Liem, and D. Wake, eda. Functional vertebrate morphology. Belknap Press, Cambridge,
Massachusetts.
Hoffstetter, R. 1958. Xenarthra. Pp. 535-636 in J. Piveteau, ed. Traite de Paleontologie, Vol. 6,
pt 2. Masson, Paris.
Holmes, W. W., and G. G. Simpson. 1931. Pleistocene exploration and fossil edentates in Florida.
Bull. Amer. Mus. Nat. Hist. 59(7):383-418.
Hulbert, R. C., Jr., and G. S. Morgan. 1993. Quantitative and qualitative evolution in the giant
armadillo Holmesina (Edentata: Pampatheriidae) in Florida. Pp. 134-177 in R. A. Martin and
A. D. Barnosky, eds. Morphological change in Quaternary mammals of North America.
Cambridge Univ. Press, Cambridge.
James, G. T. 1957 An edentate from the Pleistocene of Texas. J. Paleon. 31(4):796-808.
Kurt6n, B., and E. Anderson. 1980. Pleistocene mammals of North America. Columbia Univ.
Press, New York.
Martin, R. A. 1974. Fossil mammals from the Coleman HA fauna, Sumter County. Pp. 35-99 in
S. D. Webb, ed. Pleistocene mammals of Florida. Univ. Presses Florida, Gainesville.
Robertson, J. S., Jr. 1976. Latest Pliocene mammals from Haile XVA, Alachua County, Florida.
Bull. Florida State Mus., Biol. Sci. 20(3):111-186.
Scott, W. B. 1903a. Mammalia of the Santa Cruz Beds. Part I: Edentata, I. Dasypoda. Reports of
the Princeton University Expedition to Patagonia, 1896-1899, Volume 5:1-106.
.1903b. Mammalia of the Santa Cruz Beds. Part I: Edentata, I. Glyptodontia and
Oravigrada. Reports of the Princeton University Expedition to Patagonia, 1896-1899, Volume
5:1-227.
Webb, S. D., G. S. Morgan, R. C. Hulbert, D. S. Jones, B. J. MacFadden, and P. A. Mueller.
1989. Geochronology of a rich early Pleistocene vertebrate fauna, Leisey Shell Pit, Tampa
Bay, Florida. Quat. Res. 32:96-110.
Wetzel, R. M. 1985. Taxonomy and distribution of armadillos, Dasypodidae. Pp. 23-46 in G. G.
Montgomery, ed. The evolution and ecology of armadillos, sloths, and vermilinguas.
Smithsonian Inst. Press, Washington, D.C.
SMALL MAMMALS (INSECTIVORA, LAGOMORPHA, AND
RODENTIA) FROM THE EARLY PLEISTOCENE
(IRVINGTONIAN) LEISEY SHELL PIT LOCAL FAUNA,
HILLSBOROUGH COUNTY, FLORIDA
Gary S. Morgan' and John A. White2
ABSTRACT
Twelve species of small mammals, including one species of Insectivora, two species of Lagomorpha,
and nine species of Rodentia, are reported from the early Pleistocene (early Irvingtonian) Leisey Shell Pit
Local Fauna, Hillsborough County, Florida. Most taxa of small mammals are rare in the Leisey fauna. The
most common species is the sigmodontine rodent Sigmodon libitinus, followed in abundance by the
hydrochaerid Neochoerus sp., the arvicoline Pedomys sp., the soricid Blarina cf. B. carolinensis, the
geomyid Geomys pinetis, the giant castorid Castoroides leiseyorum, the erethizontid Erethizon dorsatum,
and the leporid Sylvilagusfloridanus. Four undescribed species of rodents occur at Leisey, three of which,
the arvicolines Pedomys and Synaptomys sp. and the large peromyscine Podomys sp., are represented by
insufficient material for formal description. Castoroides leiseyorum is described as a new species that
differs from the Rancholabrean C. ohioensis in the absence of a mesopterygoid fossa, but is similar to the
latter in size and most other morphological characters. Biochronological analysis of the rodents and
lagomorphs from Leisey indicates a late early Irvingtonian age, probably between 1.3 and 1.0 Ma. C.
leiseyorum, S. libitinus, and the undescribed species of Pedomys, Synaptomys, and Podomys are known
only from Florida late early Irvingtonian faunas. The records of S. floridanus, G. pinetis, and E. dorsatum
from Leisey are among the oldest occurrences of these extant species. Other Florida small mammal faunas
similar in age to Leisey are Haile 16A, Haile 21A, and Payne Creek Mine. Correlative early Irvingtonian
faunas from western North America include: Gilliland, Texas; Holloman, Oklahoma; Kentuck and Wathena,
Kansas; Sappa, Nebraska; and Java, South Dakota.
I The senior author is a Paleontologist at the New Mexico Museum of Natural History, 1801 Mountain Road NW, Albuquerque NM 87104-
1375, U.S.A. (formerly a Senior Biological Sciences at the Florida Museum of Natural History, University of Florida, P. O. Box 117800,
Gainesville FL 32611-7800).
Thejunior author is an Adjunct Professor in the Department of Geosciences, University of Arizona, Tucson AZ 85721. U.S.A.
MORGAN, G. S., and J. A. WHITE. 1995. Small Mammals (Insectivora, Lagomorpha, and Rodentia from
the Early Pleistocene (Irvingtonian) Leisey Shell Pit Local Fauna, Hillsborough County, Florida. Bull.
Florida Mus. Nat. Hist. 37 Pt. II(13):397-461.
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, NO. 13
RESUME
Desde la fauna local del dep6sito de conchuelas de Leisey, condado de Hillsborough, Florida, se
reportan doce species de mamiferos pequefios, incluyendo una especie del orden Insectivora, dos species de
Lagomorpha y nueve species de Rodentia provenientes del Pleistoceno temprano (Irvingtoniano temprano).
La mayoria de los taxones de pequeos maniferos son raros en la fauna de Leisey. La especie mis comnn es
el roedor sigmod6ntido Sigmodon libitinus, seguido en abundancia por el hydrochadrido Neochoerus sp., el
arvicolino Pedomys sp., el soricido Blarina cf. B. carolinensis, el geomydo Geomys pinetis, el castbrido
gigante Castoroides leiseyorum, el erethizntido Erethizon dorsatum, y el lep6rido Sylvilagus floridanus.
En Leisey existen cuatro species de roedores no descritos, tres de los cuales, los arvicolinos Pedomys y
Synaptomys sp. y el gran peromyscino Podomys sp., s encuentran represntados por insuficiente material
como para permitir una adecuada descripci6n. Castoroides leiseyorum se describe como una nueva especie
que difiere del Rancholabreano C. ohioensis por career de una fosa mesopteigoidea, atm cuando se asemeja
a la primer en tamanfo y en la mayoria de los caracteres morfol6gicos. Anilisis biocronol6gicos de roedores
y lagomorfos provenientes de Leisey indican una edad Irvingtoniana temprana tardia, probablemente de
entire 1.3 y 1.0 Ma. C. leiseyorum, S. libitinus, y la species no descritas de Pedomys, Synaptomys y
Podomys se conocen desde faunas Irvingtonianas tempranas tardias en Florida. Los registros de S.
floridanus, G. pinetis y E. dorsatum provenientes de Leisey se encuentran dentro de los mAs antiguos para
estas species actualmente existentes. Otras faunas de pequenos mamiferos de Florida similares en edad a
Leisey son Haile 16A, Haile 21A y la Mina Payne Creek. Las siguientes son faunas correlativas al
Irvingtoniano temprano del oeste de Norte America: Gilliland, Texas; Holloman, Oklahoma; Kentuck y
Wathena, Kansas; Sappa, Nebraska; y Java, Dakota del Sur.
INTRODUCTION
The small mammal fauna from the Leisey Shell Pit is composed of 12 species
belonging to the orders Insectivora, Lagomorpha, and Rodentia. The term "small
mammals" as used here refers to those orders of mammals typically consisting of
species of small body size, although two of the rodents in the Leisey fauna are
hardly small. The giant beaver Castoroides was bear-sized by some estimates and
the extinct capybara Neochoerus was larger than the largest living rodent, the
capybara Hydrochaeris. The remainder of the small mammals in the Leisey Shell
Pit LF are indeed small in body size (less than 5 kg). Two other orders of small
mammals commonly found in Florida Pleistocene vertebrate faunas, the Chiroptera
and Marsupialia, are absent from Leisey.
The Leisey Shell Pit Local Fauna (LF) includes vertebrate fossils collected
from early Pleistocene sediments of the Bermont Formation in two large, nearly
contiguous shell pits located less than 1 km inland from Tampa Bay about 7 km
southwest of Ruskin, Hillsborough County, Florida. These two shell pits, owned by
the Leisey Shell Corporation, were designated Leisey 1 and Leisey 3 by Hulbert
and Morgan (1989). Specific collecting localities within the Leisey pits are
designated by letters (e.g. Leisey lA, Leisey 3A, etc.). A third pit, Leisey 2,
contains primarily Rancholabrean vertebrates and is thus excluded from this
analysis. Hulbert and Morgan (1989) and Morgan and Hulbert (this volume)
MORGAN & WHITE: RODENTIA FROM LEISEY SHELL PIT
provided maps, coordinates, stratigraphic sections, and other information for the
individual Leisey Shell Pit sites. These two papers should be consulted for more
detailed geologic and geographic data.
Small mammals are one of the most poorly represented groups of vertebrates
in the Leisey Shell Pit LF. The Leisey small mammal fauna includes one species
of insectivore, two lagomorphs, and nine rodents. Both the species diversity and
abundance of small mammals at Leisey are low compared to several other well
known Florida Irvingtonian sites. The most abundant species, the extinct cotton
rat Sigmodon libitinus, is represented by more than 50 specimens. However, half
of the species of small mammals from Leisey are known from fewer than five
specimens. Of the two richest Leisey Shell Pit localities, Leisey IA and Leisey 3A,
the largest sample of microvertebrates is from Leisey 3A. Leisey IA yielded
remarkable samples of ungulates, ground sloths, and large carnivores, but few
terrestrial microvertebrates (Hulbert and Morgan 1989; Webb et al. 1989). The
rarity of small mammals in the Leisey Shell Pit LF is not primarily a result of
collecting bias since field crews from the Florida Museum of Natural History
screenwashed and sorted over 1 metric ton of matrix from the bone-bearing layers
in the Leisey IA and 3A sites. The hypothesized shallow marine or estuarine
depositional environment and accompanying taphonomic factors apparently had an
adverse affect on the sampling and preservation of small mammals in the Leisey
sites (Pratt and Hulbert this volume). Other small terrestrial vertebrates such as
lizards, snakes, and passerine birds are also uncommon in the Leisey Shell Pit LF
(see papers by Meylan and Emslie elsewhere in this volume).
Florida has a wealth of Irvingtonian vertebrate faunas (Morgan and Hulbert
this volume), but only a few of these have been thoroughly analyzed. The three
best known Irvingtonian vertebrate faunas from Florida prior to the discovery of
Leisey are all rich in small mammals, including the earliest Irvingtonian Inglis 1A
LF in Citrus County (Webb 1974; Kurt6n and Anderson 1980; Webb and Wilkins
1984; Morgan 1991), the early Irvingtonian Haile 16A LF in Alachua County (Ray
et al. 1981; Morgan et al. 1988; Morgan 1991), and the late Irvingtonian Coleman
2A LF in Sumter County (Martin 1974; Kurten and Anderson 1980). These three
faunas occur as cave or fissure fillings in the extensive karst terrain of northern
peninsular Florida. Morgan and Hulbert (this volume) provide synopses of the
mammalian faunas from Inglis IA, Haile 16A, and Coleman 2A, including both
large and small mammals. With the exception of Martin's (1974) comprehensive
analysis of the Coleman 2A LF and a preliminary faunal list for Inglis IA (Webb
and Wilkins 1984), most previous studies on Florida Irvingtonian small mammals
have consisted of reviews of selected taxonomic groups. The abundant
insectivores, lagomorphs, and rodents in the Inglis 1A, Haile 16A, and Coleman
2A sites are very useful for purposes of comparison with the more limited
micromammal fauna from Leisey.
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, NO. 13
ACKNOWLEDGEMENTS
We are particularly grateful to the many avocational paleontologists, including D. J. Bethea, Ralph
"Tony" Estevez, Frank A. Garcia, John Miller, James L Pendergraft, and James Ranson, who donated
important specimens of small mammals from Leisey to the Florida Museum of Natural History Vertebrate
Paleontology Collection. We thank Steven D. Emslie and Richard C. Hulbert, Jr., for their field assistance in
the Leisey screenwashing effort. David Lambert and S. David Webb helped collect sediments for
screenwashing from Leisey 3A. Arthur R. Poyer sorted the majority of the fossiliferous matrix from the two
Leisey sites. For helpful comments on the manuscript we thank Richard C. Hulbert, Jr., Robert A. Martin,
and Ann E. Pratt. Linda D. Chandler skillfully executed the drawings in Figure 6. Richard C. Hulbert, Jr.,
assisted with Figure 7. This is University of Florida Contribution to Paleobiology Number 424.
METHODS AND ABBREVIATIONS
Responsibility for the three orders of small mammals from Leisey was divided between the authors,
with GSM covering the Insectivora and Rodentia and JAW writing the section on Lagomorpha.
Measurements are in mm and were taken with either dial calipers (accurate to 0.1 mm) or a Gaertner
measuring microscope (accurate to 0.01). All Leisey specimens described here are housed in the Vertebrate
Paleontology Collection of the Florida Museum of Natural History, University of Florida, Gainesville. More
complete information on the various fossil localities discussed in the text, including field notes, detailed map
data, photographs, etc. are available in the vertebrate paleontology locality files of the Florida Museum of
Natural History.
Abbreviations used in the text are as follows:
UF Florida Museum of Natural History, University of Florida (formerly the Florida State
Museum)
LF Local Fauna
NALMA North American Land Mammal Age
Ma Mega-anna=millions of years before present
ka kilo-anna-thousands of years before present
MNI Minimum number of individuals
P/p Upper/lower premolar (e.g. P4 is the fourth upper premolar)
M/m Upper/lower molar (e.g. ml is the first lower molar)
CHRONOLOGY
Because we discuss the biochronology of the small mammals from Leisey and
other Florida Irvingtonian sites in some detail, the chronology of the Pleistocene
Epoch and the Irvingtonian Land Mammal Age are briefly summarized (see more
extensive discussion in Morgan and Hulbert this volume). The boundaries and
subdivisions of the Pleistocene follow Berggren et al. (1985) and Harland et al.
MORGAN & WHITE: RODENTIA FROM LEISEY SHELL PIT
(1990). The Pliocene/Pleistocene boundary is placed at 1.64 Ma, slightly above the
top of the Olduvai Normal Subchron of the Matuyama Chron. The Pleistocene is
subdivided into the early, middle, and late Pleistocene. The early Pleistocene
begins at 1.64 Ma and ends at the boundary between the Matuyama and Brunhes
chrons at 0.78 Ma. The middle Pleistocene covers the interval from the beginning
of the Brunhes Chron at 0.78 Ma until the onset of the last (Sangamonian)
interglacial at 130 ka. The late Pleistocene covers the period between 130 and 10
ka.
The late Pliocene and Pleistocene incorporate three North American Land
Mammal Ages: Blancan, Irvingtonian, and Rancholabrean. We follow the
definitions and subdivisions of these three NALMA proposed by Lundelius et al.
(1987). The Leisey Shell Pit LF is Irvingtonian in age and accordingly this
NALMA will be our primary focus; however, we also discuss taxa of small
mammals from the late Blancan and Rancholabrean. The Blancan/Irvingtonian
boundary is placed at about 1.9 Ma, while the Irvingtonian/Rancholabrean
boundary is about 0.3 Ma. The Blancan is entirely within the Pliocene covering
the time period from 4.5 to 1.9 Ma. Early and middle Blancan land mammal
faunas are unknown from Florida. Two late Blancan sites (between 2.5 and 1.9
Ma) containing small mammals have been reported from the state, the Haile 15A
LF in Alachua County (Robertson 1976) and the Macasphalt Shell Pit LF in
Sarasota County (Morgan and Ridgway 1987).
The Irvingtonian covers the latest Pliocene and much of the Pleistocene
(between 1.9 and 0.3 Ma), and therefore it is useful to subdivide this NALMA into
smaller units. Lundelius et al. (1987) recognized three subages of the
Irvingtonian: early Irvingtonian (Sappan), middle Irvingtonian (Cudahyan), and
late Irvingtonian (Sheridanian). The boundaries between the three Irvingtonian
subdivisions are not well defined, but their approximate age ranges are as follows:
early Irvingtonian (1.9-1.0 Ma); middle Irvingtonian (1.0-0.6 Ma); late
Irvingtonian (0.6-0.3 Ma). The early Irvingtonian covers nearly a million years
and transcends the Pliocene-Pleistocene boundary. Accordingly, this time period is
informally subdivided into the earliest Irvingtonian (1.9-1.6 Ma, latest Pliocene)
and the late early Irvingtonian (1.6-1.0 Ma, early Pleistocene). The Rancholabrean
begins about 300 ka and ends at the Pleistocene/Holocene boundary at 10 ka. The
boundary between the early Rancholabrean (300 ka-130 ka) and the late
Rancholabrean (130-10 ka) approximates the beginning of the last (Sangamonian)
interglacial high sea level stand.
Repenning (1980; 1987) and L. D. Martin (1979) both proposed
biochronologies for the Blancan through the Rancholabrean NALMA based on
evolutionary stages and immigration events of arvicoline or microtine rodents.
The Irvingtonian I and Irvingtonian II of Repenning (1987) are more or less
equivalent to the early and middle Irvingtonian, respectively, as defined above.
However, the Rancholabrean I of Repenning (1987), is essentially the same as the
late Irvingtonian recognized here and by Lundelius et al. (1987).
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, NO. 13
A mammalian biochronology that uses many different taxa of both small and
large mammals (e.g. Lundelius et al. 1987) is more applicable to Florida Plio-
Pleistocene faunas than a scheme based solely on arvicoline rodents, which are
generally rare in Florida. Many species of mammals characteristic of western and
Appalachian Irvingtonian sites are absent from Florida, whereas many Florida
Irvingtonian mammals are unknown from faunas outside the state. Martin (1974,
fig. 3.17) presented a chart showing the temporal distribution of selected Florida
Plio-Pleistocene mammals, including both small and large taxa. Based on data
from many new sites, Morgan and Hulbert (this volume) compiled a
comprehensive biochronology of Florida Plio-Pleistocene mammals. A synopsis of
their biochronology concentrating on Irvingtonian small mammals is provided in
the Discussion section.
SYSTEMATIC PALEONTOLOGY
Order INSECTIVORA Bowdich 1821
Family SORICIDAE Gray 1821
Blarina cf. B. carolinensis (Bachman 1837)
Referred Specimens.--Leisey 3A: UF 124335, left mandible with ml; UF
124336, edentulous left mandible; UF 132069, posterior half of edentulous left
mandible. MNI=3.
Description.--Three fragmentary mandibles are the only specimens of
insectivores from the Leisey Shell Pit LF. All three mandibles are considerably
larger than the least shrew, Cryptotis parva, and are similar in size to modern
mandibles of the short-tailed shrew, Blarina carolinensis, from the Florida
peninsula. The single soricid ml from Leisey (UF 124335) is also similar in
morphological characters and size (Table 1) to modern and fossil Florida
specimens of B. carolinensis. However, two slight differences were noted; the
Leisey ml seems to have a somewhat more anteroposteriorly compressed talonid
basin and the entoconid is more posteriorly placed.
Table 1 includes ml measurements (total length and trigonid length) of one
Blancan, four Irvingtonian, and two extant samples of Blarina from Florida. The
modern samples include two subspecies, B. c. carolinensis from Citrus County in
the northern half of the Florida peninsula and B. carolinensis peninsula from
Highlands County in the southern peninsula. Irvingtonian Blarina samples consist
of specimens from the earliest Irvingtonian Inglis IA LF, the early Irvingtonian
Haile 16A LF, Leisey Shell Pit, and the late Irvingtonian Coleman 2A LF. Jones et
al. (1984) examined and measured the fossil Blarina mandibles from Inglis 1A and
MORGAN & WHITE: RODENTIA FROM LEISEY SHELL PIT
Table 1. Dental measurements (in m) of Blancan, Irvingtonian, and modem Blaina from Florida. Mean,
observed range, and sample size, respectively, are provided for samples larger than one individual.
Locality Age Length of Length of
ml ml trigonid
Haile 15A
cf. Blarina
UF 17466
late Blancan
Inglis 1A
B. cf. B. carolinensis
Haile 16A
B. cf. B. carolinensis
Leisey 3A
B. cf. B. carolinensis
UF 124335
Coleman 2A
B. cf. B. carolinensis
UF 11626
Citrus County
B. c. carolinensis
Highlands County
B. c. peninsula
earliest Irvingtonian
early Irvingtonian
early Irvingtonian
late Irvingtonian
Recent
Recent
1.8
1.7-1.9
N=5
1.6
1.5-1.7
N=11
1.6
1.5-1.7
N=10
1.7
1.6-1.8
N=10
1.2
1.2
N=5
1.0
0.9-1.1
N=11
1.0
0.9-1.1
N=10
1.1
1.0-1.2
N=10
Coleman 2A, both of which they referred to B. carolinensis. The three Leisey
shrew mandibles, and in particular the ml (UF 124335), are virtually identical in
size and morphological features to the sample of Blarina from Haile 16A. The
mis from Leisey and Haile 16A are within the range of B. c. carolinensis from
northern Florida (Table 1). The Leisey shrews are tentatively referred to B.
carolinensis based on their overall similarity in morphology and size to modern
Florida samples of that species. The Inglis and Coleman Blarina, as well as extant
B. carolinensis peninsula, are larger than the Leisey specimens.
403
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, NO. 13
Remarks.-Until recently almost all extant Blarina from eastern North
America were placed in the species B. brevicauda. Jones et al. (1984)
demonstrated that B. brevicauda actually consists of at least three different species.
B. carolinensis is the living representative of this genus in the southeastern United
States. Jones et al. (1984) provided measurements of a large series of Blarina from
throughout eastern North America which showed that B. carolinensis peninsula
from southern peninsular Florida is the smallest living subspecies of North
American Blarina. However, our measurements of a sample of B. c. carolinensis
from Citrus County in northern Florida averaged slightly smaller than a sample of
B. c. peninsula from Highlands County in southern Florida (Table 1). Despite
these slight inconsistencies, the overall small size of Florida B. carolinensis is
clearly established.
The systematics of the late Blancan and Irvingtonian shrews from Florida
cannot be properly addressed here, owing to the fragmentary condition of the three
Leisey soricid specimens. Robertson (1976) reported a mandible of Cryptotis
parva (UF 17466) from the late Blancan Haile 15A LF in Alachua County. He
stated that this specimen was indistinguishable from modern Florida specimens of
C. parva, except for its slightly larger size. However, the Haile 15A shrew has an
unreduced talonid on m3, a character of Blarina (Repenning 1967), and the ml is
similar in size to mis of extant B. carolinensis and fossils from Leisey and Haile
16A (see Table 1). The key to understanding the evolutionary history of Florida
Plio-Pleistocene shrews lies in a detailed analysis of the large soricid samples from
Inglis IA and Haile 16A, both of which possess a small and a large species.
Other early Irvingtonian records of B. carolinensis, in addition to those from
Florida, include specimens from Wathena, Kansas and Java, South Dakota. Both
of these localities are outside the present range of this species (Jones et al. 1984).
Middle Irvingtonian records of B. carolinensis from Cumberland Cave, Maryland
and Hanover Quarry, Pennsylvania are also well outside the current southeastern
range of B. carolinensis.
Order LAGOMORPHA Brandt 1855
Family LEPORIDAE Gray 1821
Sylvilagusfloridanus (Allen 1890)
Referred Specimens.--Leisey 3A: UF 96220, partial right mandible with
p3; UF 96221, left p3. MNI=1.
Tentatively Referred Specimens.--Leisey 1A: UF 83120, right and left
premaxillae with left II and right 12; UF 131997, right II; UF 87965, two
associated upper cheek teeth; UF 131996, upper cheek tooth; UF 131995,
associated left II and two upper cheek teeth; UF 86229, scapula; UF 88035,
131994, distal humeri (2); UF 87966, proximal radius; UF 87963, proximal ulna;
MORGAN & WHITE: RODENTIA FROM LEISEY SHELL PIT
UF 81131, distal tibia; UF 85320, calcaneum; Leisey 3: UF 102666, distal
humerus; UF 102667, femur. MNI=2.
Description.-Among the leporid specimens from Leisey only the p3s are
described and compared in detail, as other teeth and postcranial elements of both
Sylvilagus and Lepus are generally considered to be nondiagnostic (White 1991a).
Two p3s from Leisey 3A are similar in size to the p3 of Sylvilagusfloridanus, S.
audubonii, S. transitionalis, and Lepus americanus. The measurements of the
Leisey Sylvilagus p3s are: UF 96220, length 3.1, width 3.0; UF 96221, length 3.0,
width 2.5. The enamel pattern of these two teeth most closely resembles that of the
p3 of S. floridanus in the presence of a single anterior reentrant, the lack of folding
of the thick enamel on the anterior edge of the posteroexternal reentrant, and
minimal folding of the thin enamel on the posterior edge of this reentrant (Fig.
1A). The Leisey p3s differ from S. bachmani and S. nuttallii by their larger size,
from S. aquaticus, S. palustris, and S. cunicularius by smaller size, and from S.
brasiliensis by the lack of multiple anterior reentrants. The recently described S.
webbi (White 1991b) from the late Blancan and early Irvingtonian of Florida
differs from the Leisey p3s in larger size, greater number of anterior reentrants,
and more complex enamel folding. The Leisey specimens are referred to S.
floridanus based on the similarity in size and enamel pattern of p3.
Remarks.-Leporids are notoriously difficult to identify from most cranial,
dental, and postcranial remains. Paleontologists studying this family have tended
to base their systematic conclusions on the structure of the p3, and to a lesser
extent the P2 (e.g. White 1991a,b). The identification of Sylvilagus floridanus
from the Leisey Shell Pit is based on two p3s from Leisey 3A. The referral of the
additional teeth and postcranial elements from Leisey 1A and Leisey 3 to this
species is based entirely on their small size, and therefore these identifications
should be considered tentative.
The first Sylvilagus to appear in the Florida fossil record is S. webbi from the
late Blancan Macasphalt Shell Pit and Kissimmee River local faunas. S. webbi
also occurs in the earliest Irvingtonian Inglis 1A and De Soto Shell Pit local faunas
and the late early Irvingtonian Haile 16A. Records of S. floridanus from Leisey
and the correlative early Irvingtonian Payne Creek Mine and Haile 21A local
faunas represent the earliest occurrence of this living species in Florida. The oldest
records of S. floridanus are from the earliest Irvingtonian Curtis Ranch LF,
Arizona and Vallecito Creek LF, California (White 1991a). Hibbard and Dalquest
(1966) reported Sylvilagus cf. S. floridanus from the late early Irvingtonian
Gilliland LF in Texas, a close correlative of Leisey based on the large mammal
fauna (Morgan and Hulbert this volume).
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, NO. 13
C
Figure 1. (A) Sylvilagusfloridanus, Leisey 3A, right p3 (reversed) UF 96220; (B) Lepus cf. L. townsendii,
Leisey IA, left p3, UF 82165; (C) Geomys pinetis, Leisey IA, left P4, UF 87225. Scale bar 1 mm in length
for A and B and 2 mm in length for C.
Lepus cf. L. townsendii Bachman 1839
Referred Specimen.-Leisey 1A: UF 82165, left mandible with p3-p4.
MNI=1.
Tentatively Referred Specimens.-Leisey 1A: UF 83659, distal humerus;
UF 131992, partial innominate; UF 131993, distal femur.
Description.-The Leisey Lepus p3 can be distinguished from Sylvilagus
aquaticus, S. palustris, and S. cunicularius by the single, slightly incised anterior
reentrant and from all other species of Sylvilagus by its larger size (Fig. 1B).
Measurements of the single p3 of Lepus (UF 82165) from Leisey are: length 3.5,
MORGAN & WHITE: RODENTIA FROM LEISEY SHELL PIT
width 3.1. The Leisey tooth can be distinguished from Lepus californicus, L.
alleni, L. callotis, and L. flavigularis by the slightly incised anterior reentrant,
from L. americanus by the posteroexternal reentrant which extends to the lingual
border of p3, and from L. alleni, L. arcticus, and L. othus by being smaller in size,
falling below the observed ranges of the latter.
The Leisey p3 is tentatively referred to Lepus townsendii because it more
closely resembles that species than other members of the genus. However, there
are two features in which the Leisey tooth differs from extant L. townsendii. The
anterior external reentrant on the Leisey p3 is slightly less well incised than in any
of the 22 modern specimens of L. townsendii used for comparison. Also, Figure 1B
shows that on UF 82165 from Leisey, the thin enamel on the posterior edge of the
posteroexternal reentrant is moderately crenulated or folded. White (1991a) noted
that this thin enamel was typically folded in L. californicus and unfolded in L.
townsendii. The Leisey tooth differs from L. californicus and the extinct species L.
benjamin from the early Irvingtonian Anita LF in Arizona (Hay 1921) by its
shallower anterior reentrant and less complicated enamel. The Leisey Lepus is
smaller than L. giganteus from the middle Irvingtonian Conard Fissure LF in
Arkansas (Brown 1908).
The Leisey p3 differs from a large sample of Lepus p3s from the Inglis 1A LF
in its smaller size, particularly the width. The Leisey and Inglis p3s are similar in
having both the anterior reentrant and anteroexternal reentrant weakly incised.
The thin enamel on the posterior edge of the posteroexternal reentrant ranges from
simple and unfolded in some Inglis specimens to moderately crenulated in other
Inglis specimens and the Leisey tooth. Further study of the Inglis sample may
reveal that an undescribed species is present in Florida Irvingtonian faunas, but for
now the Inglis jackrabbits are identified only as Lepus sp.. Both the Inglis IA and
Coleman 2A Lepus have been referred to L. alleni (see Martin 1974; Webb and
Wilkins 1984). However, the p3s of the Inglis IA Lepus can be distinguished from
L. alleni by the weakly incised anterior reentrant and the lack of highly folded
enamel. The Lepus sample from Coleman 2A consists entirely of postcranials
(Martin 1974).
Remarks.-The identification of Lepus cf. L. townsendii from Leisey is based
on a mandible with p3-p4. The three postcranial elements are tentatively referred
to this species on the basis of their very large size compared to other leporid
postcranials from Leisey. Lepus was first reported from Florida in the Coleman 2A
and Inglis lA Irvingtonian faunas (Martin 1974). Previously unreported
specimens of Lepus from Florida include a femur from the middle Irvingtonian
McLeod LF in Levy County and an edentulous mandibular symphysis (UF 128991)
from the late early Irvingtonian Payne Creek Mine. The fossil record indicates that
in Florida Lepus is restricted to the Irvingtonian.
The white-tailed jackrabbit Lepus townsendii is an extant species found on the
Great Plains as far east as Illinois. Although Lundelius et al (1987) used the first
407
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, NO. 13
appearance of the genus Lepus as one of the defining taxa for the Irvingtonian
NALMA, Lepus is now known from at least two very late Blancan faunas, Big
Springs, Nebraska and Borchers, Kansas (White 1991a). White noted that both of
these faunas contained some p3s that resembled L. townsendii and others that were
more similar to L. californicus. This is very reminiscent of the sample of Lepus
p3s from the Inglis IA LF. Inglis is only slightly younger than Big Springs and
Borchers, and represents the earliest record of Lepus in Florida.
Order RODENTIA Bowdich 1821
Family GEOMYIDAE Gill 1872
Geomys pinetis Rafinesque 1806
Referred Specimens.-Leisey 1A: UF 87225, partial right and left maxillae
with left P4; UF 80044, 87964, right I1 (2); UF 88031, left II; UF 125202, left
mandible with il, p4-m2; UF 83625, left mandible with p4; UF 81827, left il; UF
83829, distal humerus. Leisey 3A: UF 125208, proximal ulna. Leisey 3: UF
124564, right mandible with il, p4-ml. MNI=3.
Description.-Four specimens of Geomys from the Leisey Shell Pit LF, three
from Leisey lA and one from Leisey 3A, provide sufficient morphological
information to permit an identification to the species level. A portion of the right
and left maxillae with a P4 (UF 87225; Fig. IC) is particularly significant, as the
P4 is perhaps the single most diagnostic tooth used to document the evolutionary
history of Geomys during the late Pliocene and Pleistocene of Florida (Wilkins
1984). The Leisey P4 is comparatively large (anteroposterior length 2.3, width of
posterior loph 2.4) and totally lacks enamel on its posterior surface. Wilkins
(1984) did not provide measurements of the upper dentition of Florida fossil
Geomys, and thus no comparative measurements of the P4 are presented here. One
or more P4s of Geomys are known from three other Irvingtonian sites in Florida:
Inglis IA, Haile 16A, and Coleman 2A. Wilkins (1984) stated that the Geomys
from Inglis IA and Haile 16A possessed enamel on at least half up to the entire
posterior surface of P4, while specimens from Coleman 2A, as well as extant G.
pinetis, lacked enamel in this region.
In an examination of the larger sample of Geomys now available from Haile
16A, a wider range of variation was noted in the amount of enamel on the posterior
surface of P4 than was observed by Wilkins (1984). Because of its taxonomic
importance, this character was re-examined for all Florida Blancan and
Irvingtonian Geomys. Among 20 randomly selected P4s of the extinct species G.
propinetis (Wilkins 1984) from Inglis lA (out of a total sample of over 100), 15
teeth (75%) have from 50-100% coverage of enamel on the posterior surface, 4
teeth (20%) have less than 50% coverage, and- on 1 tooth the enamel is almost
absent (coverage less than 5%, but still perceptible). The entire sample of 16 P4s
MORGAN & WHITE: RODENTIA FROM LEISEY SHELL PIT
of G. propinetis from Haile 16A was examined, of which only 4 teeth (25%) have
50-100% enamel coverage on the posterior surface, 7 teeth (44%) have less than
50% coverage, and in 5 teeth (31%) the enamel coverage is nearly to totally absent.
Two P4s of Geomys (UF 100342, 104493) from the late Blancan Macasphalt Shell
Pit LF in Sarasota County, Florida were examined as well. Both of these teeth are
very similar to the majority of specimens of G. propinetis from Inglis 1A in having
nearly total coverage of enamel on their posterior surface. The single Geomys P4
from Leisey and a sample of six P4s from Coleman 2A resemble modern G. pinetis
in lacking enamel on their posterior surface.
The progressive loss of enamel on the posterior surface of P4 in Florida fossil
Geomys from the late Pliocene and early Pleistocene provides a good indicator of
age. G. propinetis from the late Blancan Macasphalt Shell Pit LF and the earliest
Irvingtonian Inglis 1A LF is characterized by having more than 50% of the
posterior surface of P4 covered with enamel in most individuals, as well as by
small size. Although the Geomys from Haile 16A is referred to G. propinetis
following Wilkins (1984), the enamel on the posterior edge of P4 in this sample is
reduced compared to the two older samples. More than half of the P4s from Haile
16A have less than 50% enamel coverage on the posterior surface, including two
teeth in which enamel is completely absent. It is not surprising that the Haile 16A
Geomys is somewhat advanced over the sample from Inglis 1A, as other data
suggest that the former site is younger. This character must have been evolving
rapidly during the early Irvingtonian, because in the late early Irvingtonian Leisey
Shell Pit LF, enamel was totally absent on the posterior surface of P4, a trait found
in all younger samples referred to G. pinetis. P4s of G. pinetis from Leisey and
Coleman 2A, as well as modern specimens of this species, are larger than those of
G. propinetis from Haile 16A, Inglis IA, and Macasphalt.
Another important evolutionary trend in Florida Geomys is the increasing
size and depth of the retromolar fossa through time (Wilkins 1984). The
retromolar fossa is a pit located on the dorsal surface of the mandible posterolabial
to the m2 and m3, and lingual to the coronoid process. The increase in size of the
retromolar fossa is evident in the increasing distance between the base of the
coronoid process and the toothrow labial to m2 and m3. The retromolar fossa is
short, narrow, and very shallow in the Inglis IA sample (Wilkins 1984). This
fossa is noticeably longer and much deeper in modern G. pinetis, and in fossil
mandibles referred to this species from Leisey and Coleman. The anterior edge of
the retromolar fossa is located posterolabial to the m2 and forms a nearly vertical
plate in G. pinetis, whereas the anterior margin slopes gradually posteriorly in
mandibles of G. propinetis from Inglis. Although no mandibles from Haile 16A
preserving the retromolar fossa were available to Wilkins for study, one mandible
is now known from this site (UF 69117) that preserves the anterior half of the
retromolar fossa. The complete length and depth of the retromolar fossa cannot be
determined from this specimen, but enough of this structure is preserved to confirm
that it is very shallow and has a gently sloping anterior margin as in the Inglis
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II NO. 13
mandibles. The Leisey and Coleman mandibles are similar to modern G. pinetis in
the size and depth of the retromolar fossa.
A third trend Wilkins (1984) observed in Florida Geomys was an increase in
body size, using the observed range in width of the lower incisor as a size
indicator. Although Wilkins (1984) noted that the width of il is dependent on the
ontogenetic age of the individual, the maximum width of the il has increased
through time. Only two lower incisors of Geomys are known from Leisey with
widths of 1.7 and 2.2 mm (Table 2). Based on measurements in Wilkins (1984),
this is slightly smaller than the maximum width of the il in modern G. pinetis (2.5
mm) and the range of lower incisor widths observed in the Coleman sample (1.9-
2.5 mm). The maximum width of the Leisey lower incisors is broader than the ils
of G. propinetis from Inglis 1A in which the maximum width is 1.9 mm (Wilkins
1984). Measurements of the two most complete mandibles of Geomys from Leisey
are compared in Table 2 to mandibles from Haile 16A and Coleman 2A. Wilkins
(1984) should be consulted for mandibular measurements of G. propinetis from
Inglis lA and Recent G. pinetis. The measurements presented here and those of
Wilkins (1984) indicate that the Leisey Geomys is intermediate in size between the
smaller G. propinetis from Inglis lA and Haile 16A and the somewhat larger
specimens of G. pinetis from Coleman 2A. The maximum size of modern G.
pinetis apparently was achieved by the late Irvingtonian (Wilkins 1984).
Remarks-Pocket gophers of the genus Geomys are first recorded in Florida
from the late Blancan Macasphalt Shell Pit and Haile 15A local faunas (Morgan
and Ridgway 1987). Based on small size and presence of enamel on the posterior
surface of P4, the Macasphalt sample is referred to G. propinetis, an extinct species
originally described from the earliest Irvingtonian Inglis lA LF (Wilkins 1984).
The Haile 15A Geomys sample lacks a P4, but does possess a single specimen of
the diagnostic M3 (Wilkins 1984) that closely resembles the M3 of G. propinetis.
A small sample of Geomys recently identified from the earliest Irvingtonian De
Soto Shell Pit in De Soto County, a correlative of Inglis IA, lacks the P4, M3, and
mandibles, but is tentatively referred to G. propinetis on the basis of small size and
age. The Geomys sample from Haile 16A is referred to G. propinetis following
Wilkins (1984), but is somewhat more advanced than the Inglis pocket gopher in
characters of the P4 and slightly larger size. The Geomys sample from the Leisey
Shell Pit LF possesses characters of the extant species, G. pinetis, including the
lack of enamel on the posterior surface of P4 and a large, deep retromolar fossa on
the mandible, but is somewhat smaller. The living southeastern pocket gopher, G.
pinetis, first appears in Florida at Leisey, presumably having evolved in situ from
G. propinetis during the early Irvingtonian. It is difficult to correlate the Florida
Irvingtonian Geomys with other North American pocket gophers belonging to this
MORGAN & WHITE: RODENTIA FROM LEISEY SHELL PIT
Table 2. Measurements (in mm) of lower incisors and cheek teeth of selected Irvingtonian Geomys from
Florida. Description of measurements follows Wilkins (1984).
anterior posterior
width length width width width
Locality il p4 p4 p4 ml
Haile 16A
UF 69116 1.7 2.5 1.4 2.0 2.0
UF 69117 1.9 2.8 1.7 2.1 -
Leisey Shell Pit
UF 125202 2.2 2.7 1.8 2.5 2.3
UF 125564 1.7 2.7 1.5 2.2 2.2
UF 83625 2.7 1.5 2.2 -
Coleman 2A
UF 45861 2.5 2.8 1.7 2.4 2.6
UF 45864 2.2 2.9 1.6 2.3 2.4
UF 15001 2.9 1.9 2.5 -
genus because fossils of both G. propinetis and G. pinetis are restricted to Florida
(Wilkins 1984). The extant species G. pinetis has a rather limited distribution as
well, occurring only in Florida, Georgia, and Alabama.
Family CASTORIDAE Gray 1821
Castoroides leiseyorum new species
Holotype.-UF 81736, posterior half of skull from Leisey Shell Pit 1A,
Hillsborough County, Florida, Bermont Formation, late early Irvingtonian.
Collected by Frank A. Garcia in August 1984.
Paratypes.-UF 60868, posterior half of skull from Leisey 1, collected by
Frank A. Garcia in 1983; UF 115965, left mandible with il, p4-m3 from Leisey 3,
collected by Ralph Estevez and John Miller on 30 March 1988.
Referred Specimens.-Leisey 1A: UF 66000, incisor fragment; UF 83119,
86862, astragalus (2). Leisey 3B: UF 132047, partial cheektooth; Leisey 3: UF
124563, partial cheektooth. MNI=3.
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, NO. 13
Diagnosis.--Castoroides leiseyorum can be differentiated from C. ohioensis,
the only other currently recognized species in the genus, by the absence of a
mesopterygoid fossa on the basisphenoid. In C. leiseyorum, the basisphenoid bears
a shallow elongated groove in the anatomical position where the deeply concave,
ovate mesopterygoid fossa is located in C. ohioensis. C. leiseyorum can also be
separated from C. ohioensis by characters of the lambdoidal crest. In C.
leiseyorum this crest is lower and more rounded, and in dorsal view is strongly
convex posterolaterally with a deep V-shaped identation along the midline where it
meets the sagittal crest. The lambdoidal crest is higher and sharper in C.
ohioensis, and in dorsal view is more nearly parallel to the posterior margin of the
skull. C. leiseyorum can be distinguished from Procastoroides sweeti by its larger
size and the presence of well-developed longitudinal ridges and grooves on the
incisors. C. leiseyorum differs from P. idahoensis in its larger size and by the
presence of isolated enamel laminae on all lower cheek teeth resulting from the
absence of enamel at the labial termination of the paraflexid and mesoflexid and
the lingual termination of the hypoflexid.
Etymology.-Named for Bud Leisey and members of his family, as well as for
the employees of the Leisey Shell Corporation. The study of paleontology in
Florida has benefitted immeasurably from their cooperation and generosity.
Description.-The mandible and two braincases of Castoroides from Leisey
are the most complete fossils of the giant beaver yet found in Florida. A nearly
perfect left mandible (UF 115965) has a complete dentition, including an intact
lower incisor. The mandibular ramus is virtually complete, with the exception of
the coronoid process, the posterolateral portion of the capsular process, the
posteriormost extremity of the angular process, and a portion of the ventral margin
external to the incisor (Figs. 2A-C). The two partial skulls are nearly intact
posterior to the interorbital constriction.
The mandible of Castoroides leiseyorum from Leisey was directly compared
with specimens of C. ohioensis from various Florida Rancholabrean sites and with
published descriptions, figures, and measurements of other complete mandibles of
C. ohioensis from elsewhere in eastern North America. The Leisey mandible also
was compared to literature descriptions and figures of the two Blancan taxa of
giant beavers, Procastoroides sweeti (Barbour and Schultz 1937; Woodburne
1961) and P. idahoensis (Shotwell 1970). Like C. ohioensis, the lower incisor of
the C. leiseyorum is strongly ridged or crenulated. The p4 of C. leiseyorum is very
similar to that of typical C. ohioensis from the Rancholabrean. In both of these
forms the paraflexid, mesoflexid, and hypoflexid extend entirely across the tooth
from the labial to the lingual margin thereby completely isolating the four lophids
as complete enamel laminae (dental terminology for castorid teeth follows
Woodburne 1961). The mesoflexid and hypoflexid are also complete on the ml-
MORGAN & WHITE: RODENTIA FROM LEISEY SHELL PIT
Figure 2. Castoroides leiseyorum new species, Leisey 3, left mandible with il, p4-m3 (paratype), UF
115965. (A) lateral view, (B) medial view, (C) dorsal view. Scale bar 30 mm in length.
***
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, NO. 13
Table 3. Measurements (in amm) of the lower dentition of Castoroides and Procastoroides. Abbreviations
are: L (length) and W (width). Mean, observed range, and sample size, respectively, are provided for all
samples, except the single Leisey specimen
Species alveolar occlusal
length length L W L
p4-m3 p4-m3 ii il p4
Procastorides sweet 50.3 11.5 10.4 12.3
Blancan 50-51 10.6-12.8 9.6-12.0 9.2-14.2
Kansas1 N=3 N=4 N=4 N=13
Procastoroides idahoensis 60.5 14.9 14.8 14.9
Blancan 14.6-15.1
Idaho2 N=1 N=1 N=1 N=3
Castoroides leiseyorum
Leisey Shell Pit
UF 115965 73.2 69.6 23.3 20.8 22.1
Castoroides ohioensis 68 67 24.9 20.3 19.5
Florida 22.4-29.3 18.6-21.6 14.6-24.5
N=1 N=1 N=7 N=7 N=6
Castoroides ohioensis 71.0 23.6 20.8 19.5
(exclusive of Florida)3 70-72 20-27 20-22 19-20
N=2 N=5 N=5 N=2
Measumensm from Woodbume (1961).
2Mearments Dom Shotwea (1970).
m3 and isolate the three lophids on each of these teeth. Furthermore, the enamel
on the labial margin of the lophids is thin on all four cheekteeth of C. leiseyorum,
especially on the labial edge of the median lophid. The lower cheekteeth of the
Leisey mandible are similar in size to those of C. ohioensis from the
Rancholabrean (Table 3). There appear to be no obvious differences between C.
leiseyorum and C. ohioensis in the lower dentition and mandibular ramus.
Shotwell (1970) described the species Procastoroides idahoensis from the late
Blancan Grand View LF in Idaho. Unlike the earlier Blancan species, P. sweeti, P.
idahoensis has well developed longitudinal ridges on the incisors, like Castoroides.
P. idahoensis is distinguished from Castoroides primarily by its smaller size, but
also by the tendency for enamel to be present at the labial termination of the
paraflexid and mesoflexid and lingual termination of the hypoflexid on the p4.
MORGAN & WHITE: RODENTIA FROM LEISEY SHELL PIT
Table 3 Extended.
W L W L W L W
p4 ml ml m2 m2 m3 m3
9.0 11.4 9.3 11.1 8.9 9.8 8.2
8.3-11.3 10.2-13.0 7.6-10.2 9.5-12.5 7.8-10.0 9.0-11.0 6.6-9.2
N=13 N=7 N=7 N=9 N=9 N=5 N=5
11.3 12.0 13.1 11.4 10.9
10.8-11.7 -
N=3 N=1 N=1 N=1 N=1
16.4 16.6 13.9 17.3 14.1 18.8 12.8
15.5 16.5 13.7 15.8 14.6 15.5 12.9
13.4-17.4 16.4-16.6 12.5-14.9 -
N=6 N=2 N=2 N=1 N=1 N=1 N=1
14.0 16.5 14.5 17.0 14.0 16 12
12-16 16-17 13-16 17 13-15 -
N=2 N=2 N=2 N=2 N=2 N=1 N=1
3 Measurmnts fiom Hay (1914) d Brbour (1931).
These terminations are composed of much thinner enamel than on the remainder
of the tooth. In certain p4s of P. idahoensis, including the type, the paraflexid,
mesoflexid, and hypoflexid extend entirely across the tooth as in Castoroides. The
ml from the type of P. idahoensis also has isolated enamel lophids like the p4;
however, on the m2 of this specimen the medial and posterior lophids are
connected by enamel at the lingual termination of the hypoflexid (Shotwell 1970).
All of the lophids are isolated as complete enamel laminae on the four lower
cheekteeth of the C. leiseyorum mandible.
Martin (1969) described an extinct subspecies of Castoroides, C. ohioensis
dilophidus, from the Rancholabrean Santa Fe River 2 locality in northern
peninsular Florida. This subspecies is characterized by the division of the 2nd
anterior lophid on the p4 into two isolated elliptical enamel laminae. In C.
ohioensis from elsewhere in North America both the 1st and 2nd anterior lophids
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, NO. 13
on p4 are undivided, consisting of single laminae. The single p4 of C. leiseyorum
lacks the divided 2nd anterior lophid, and thus has the typical morphology of C.
ohioensis.
The two braincases of Castoroides leiseyorum from Leisey (Figs. 3-4) provide
much information on the posterior half of the skull. Stirton (1965) published
excellent descriptions and figures of the skull of C. ohioensis. Detailed
morphological comparisons were made between the two Leisey skulls and the
figures and descriptions of C. ohioensis from Stirton. Cranial measurements are
provided for the two skulls of C. leiseyorum (Table 4), and where possible, these
are compared to measurements of five of the most complete skulls of late
Pleistocene C. ohioensis (from Stirton 1965:276). Barbour and Schultz (1937, fig.
2) figured the holotype skull of Procastoroides sweet from the Broadwater LF in
Nebraska in dorsal and lateral views, and provided a very brief morphological
description. They presented five cranial measurements for P. sweet; however,
most of these were based on a nearly complete skull (total length, zygomatic
breadth, etc.), and thus cannot be compared to the incomplete Leisey skulls.
Martin and Schultz (1985) figured and described a braincase of P. idahoensis from
the late Blancan Seneca LF of Nebraska, but provided no measurements.
In most features of the braincase, Castoroides leiseyorum does not appear to
differ significantly from C. ohioensis. Likewise, almost every one of the
measurements taken on the two Leisey skulls (Table 4) is within the range of
variation of the five C. ohioensis skulls measured by Stirton (1965). Many authors
(e.g. Hay 1914; Stirton 1965) have noted that Castoroides is unique in possessing
two separate posterior openings for the internal nares, one dorsal and one ventral.
The posterodorsal opening, termed the mesopterygoid fossa by Stirton (1965), is
perhaps the most unusual cranial feature of Castoroides, consisting of a large, deep
fossa in the basisphenoid. The mesopterygoid fossa is ovate in outline, very deep,
and opens anterodorsally into the internal narial passage. The ventral floor of this
fossa is formed by expanded processes of the pterygoids. In a skull of C. ohioensis
from McClean County, Illinois described by Stirton (1965), the mesopterygoid
fossa is 23.0 mm in length and 15.8 mm in width. In another skull of C. ohioensis
from Logansport, Indiana this opening is 25 mm long and 16 mm wide (Hay
1914).
Surprisingly, the dorsal mesopterygoid fossa, which is so characteristic of
Castoroides ohioensis, is completely absent in the two braincases of C. leiseyorum,
both of which have reasonably complete basicranial regions (Figs. 3B, 4B). In the
two Leisey skulls, the basisphenoid is well preserved and it lacks the large, deep,
ovate fossa for the posterodorsal opening of the internal narial passage. Instead,
the basisphenoid in C. leiseyorum bears a slightly concave, elongated groove along
the midline. This groove connects anteriorly to the internal narial opening in the
paratype skull (UF 60868), although that portion of the basicranial region anterior
to the basisphenoid is absent in the holotype (UF 81736). Both Leisey skulls are
MORGAN & WHITE: RODENTIA FROM LEISEY SHELL PIT
Figure 3. Castoroides leiseyorum new species, Leisey 1A, braincase holotypee), UF 81736. (A) dorsal
view; (B) ventral view; (C) posterior view. Scale bar 30 mm in length.
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 37, PT. II, NO. 13
Figure 4. Castoroides leiseyorum new species, Leisey 1, braincase (paratype), UF 60868. (A) dorsal view,
(B) ventral view. Scale bar 30 nun in length.
418
Table 4. Selected cranial measurements (in mm) of Castoroides leiseyorum from the Leisey Shell Pit LF and late Pleistocene Castoroides ohioensis. Means and
observed ranges, respectively, for the C. ohioensis sample were computed from measurements of five of the most complete skulls of this species from
Rancholabrean sites in the northern United States provided by Stirton (1965, p. 276).
width of width of width of breadth of breadth of height of
postzygomatic mastoid paroccipital depth of occipital foramen foramen
Species constriction processes processes braincase condyles magnum magnum
Castoroides leiseyorum
Leisey Shell Pit
UF 60868 79.8 62.8 57.0 31.6 18.7
UF 81736 77.8 141.4 109.6 60.6 62.3 33.4 19.3
Castoroides ohioensis 81.2 152.4 111.6 64.9 66.5 30.4 15.4
Rancholabrean 71.5-88.2 136.5-167.0 101.0-123.0 62.2-68.0 -
N=5 N=5 N=5 N=5 N=I N=1 N=1
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, NO. 13
damaged in the pterygoid region, but appear to have possessed expanded pterygoid
processes that would have formed a ventral floor beneath the anterior portion of the
basisphenoid, as in C. ohioensis.
Based on the presence of an incipiently concave basisphenoid that connects
anteriorly to the internal narial opening and a ventral floor formed by the
pterygoids, it appears that the two early Pleistocene Castoroides skulls from Leisey
possessed the early morphological stages of the deep mesopterygoid fossa and
double internal nares characteristic of the late Pleistocene C. ohioensis. The
timing of the earliest appearance of a fully developed mesopterygoid fossa in
Castoroides must await the discovery of skulls from middle and late Irvingtonian
sites. The basicranial region in the two species of Procastoroides has not been
described, although braincases are known for both P. sweeti and P. idahoensis
(Barbour and Schultz 1937; Martin and Schultz 1985).
The basioccipital of the two Castoroides leiseyorum skulls also appears to be
somewhat different from Rancholabrean specimens of C. ohioensis. There is a
slight ridge along the midline of the basioccipital in the Leisey skulls and the
portion of the basioccipital lateral to this ridge is only slightly concave. In C.
ohioensis, the median ridge is higher and sharper and laterally the basioccipital is
more concave. Both species of Castoroides are very different from the modern
beaver Castor in the basicranial region. Castor lacks a concavity in the
basisphenoid and has only a single internal narial opening. However, Castor has a
very prominent, deep, rectangular fossa that occupies virtually the entire
basioccipital. There is no evidence of a concavity in the basioccipital in either
species of Castoroides.
The lambdoidal crests in the two braincases of Castoroides leiseyorum differ
in shape from typical C. ohioensis. In the two Leisey Castoroides skulls the
lambdoidal crest is lower and more rounded. In dorsal aspect this crest is strongly
convex or rounded posterolaterally and then curves sharply anteriorly for a distance
of 15-20 mm at the midline forming a very distinct V-shaped outline (see Figs. 3A,
4A). The lambdoidal crest of C. ohioensis is sharper and more vertical, and in
dorsal view is more parallel to the posterior margin of the skull meeting the
sagittal crest at nearly a right angle.
Remark.-The Leisey Shell Pit LF has produced the best preserved fossils of
Castoroides known from Florida. Isolated teeth, especially fragments of the
characteristic ridged incisors, as well as limb bones are relatively common in
certain Florida Rancholabrean sites, but more intact material is extremely scarce.
A few partial mandibles with cheekteeth and several unbroken incisors were the
most complete specimens of the giant beaver known from Florida prior to the
discovery of Leisey.
The Leisey Shell Pit LF represents the oldest well-documented occurrence of
Castoroides in Florida. The only other securely dated Irvingtonian record of
Castoroides from Florida consists of a complete upper incisor (UF 17318), two
MORGAN & WHITE: RODENTIA FROM LEISEY SHELL PIT
isolated cheekteeth (UF 17319-17320), and an atlas (UF 133904) from the Crystal
River Power Plant LF in Citrus County, an early Irvingtonian correlative of Leisey.
A fragmentary braincase of Castoroides (UF 60860) from Apollo Beach, located
about 10 km north of Leisey, is probably Irvingtonian as well, although the Apollo
Beach fauna is a mixed assemblage containing both Irvingtonian and
Rancholabrean taxa. The Apollo Beach Castoroides skull lacks the critical
basicranial region, and thus can not be definitely referred to C. leiseyorum.
Martin (1969) reported three isolated teeth and an incisor fragment of
Castoroides sp. from the supposed late Blancan Santa Fe IB Site in Columbia
County in northern peninsular Florida. However, examination of the mammalian
fauna from Santa Fe 1B reveals that this site, like many of the Santa Fe faunas,
consists of a mixture of late Blancan and Rancholabrean taxa (Morgan and
Ridgway 1987; Morgan and Hulbert this volume). Based on the absence of
Castoroides from all other late Blancan and earliest Irvingtonian faunas in Florida,
it appears highly probable that the Santa Fe IB teeth are Rancholabrean in age.
Removing this single questionable Blancan record, C. leiseyorum from the Leisey
Shell Pit appears to be the oldest well documented sample of Castoroides. C.
leiseyorum probably was derived from a species of Procastoroides sometime
during the late Blancan or earliest Irvingtonian.
Martin (1969) summarized the systematics and distribution of Castoroides
ohioensis in Florida. He listed 25 Rancholabrean faunas from Florida containing
C. ohioensis, most of which sampled freshwater depositional environments.
Martin described the subspecies C. ohioensis dilophidus from several late
Pleistocene localities in the Sante Fe River system. Martin (1975) later reported
specimens of C. ohioensis dilophidus from Rancholabrean deposits in the
Waccasassa River in Levy County, Florida. The UF Collection now has additional
material of C. ohioensis dilophidus from the Oklawaha River and Withlacoochee
River in Marion County and from a site near the Suwannee River at Branford in
Suwannee County. Although Martin (1969, 1975) suggested that C. ohioensis
dilophidus was restricted to the Santa Fe River and its drainages during the late
Pleistocene, these new records indicate that C. ohioensis dilophidus was more
widespread in northern peninsular Florida during the late Pleistocene.
Family ERETHIZONTIDAE Thomas 1897
Erethizon dorsatum (Linnaeus 1758)
Referred Specimens.-Leisey 3: UF 124632, left mandible with p4-m2; UF
128200, left mandible with p4-m3 (cast); UF 135669, left mandible with il, ml-
m2. MNI=3.
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, NO. 13
Description.-The three Leisey porcupine mandibles (Figs. 5A-C) are similar
to Erethizon and differ from Coendou in the characters discussed by White (1968,
1970) and Frazier (1981). Among other characters, these two genera can be
separated by the degree of anterior to posterior divergence of the lower toothrows
from the midline. The lower toothrows of Coendou are parallel or subparallel,
diverging from the midline only slightly posteriorly, whereas the toothrows of
Erethizon diverge noticeably. In an isolated mandible the degree of divergence can
be estimated by drawing an imaginary line through the longitudinal axis of the
toothrow. In Coendou this line generally falls lateral to the lower incisor and in
Erethizon it falls medial to the incisor. In the three Leisey mandibles the
toothrows diverge strongly from the midline from anterior to posterior, and a line
projected through the toothrows falls medial to the incisor, both of which suggest
referral to Erethizon.
With the exception of the small species Erethizon kleini from Inglis 1A, the
Leisey mandibles and all other Florida erethizontid fossils are larger than living
species of the Neotropical porcupine Coendou (see comparative measurements of
Erethizon and Coendou in Frazier 1981). There is no overlap in size between
these two genera in the alveolar length of the lower toothrow. The largest
mandible of Coendou from a sample of 114 measured by Frazier (1981) had an
alveolar toothrow length of 23.7 mm (sample mean = 19.4), while the smallest
Erethizon from a sample of 154 was 25.3 mm (sample mean = 29.1). The two
Leisey mandibles in which this measurement can be taken both have alveolar
toothrows in excess of 31 mm (Table 5), placing them well above the size range of
Coendou and near the maximum size for the living porcupine, Erethizon dorsatum.
Frazier (1981) distinguished Erethizon kleini from E. dorsatum primarily on
the basis of its smaller size. The three porcupine mandibles from the Leisey Shell
Pit LF are considerably larger than E. kleini (see measurements in Table 5). The
Leisey mandibles are within the range of variation of E. dorsatum in all available
measurements, but are generally larger than the average modern E. dorsatum. The
Inglis Erethizon jaws and lower teeth are either smaller than E. dorsatum or are at
the low end of the range of variation of the modern species. Other Irvingtonian
specimens from Florida referred to E. dorsatum also tend to be large (Table 5). On
the basis of both size and morphology the porcupine mandibles from Leisey are
indistinguishable from extant E. dorsatum.
Remarks.-Frazier (1981) reviewed the fossil history of North American
porcupines. He described a new small species of Erethizon, E. kleini, from the
earliest Irvingtonian Inglis lA LF, along with two referred maxillae from Merritt
Island in Brevard County. Frazier reported E. dorsatum from several Florida
Irvingtonian sites, including Haile 16A, Apollo Beach, and Coleman 2A. The
Erethizon mandibles from Leisey and Haile 16A are very similar in size and
morphology, reflecting the overall similarity between the rodent faunas in these
two sites (Table 5). Although smaller in some measurements, the sample of three
MORGAN & WHITE: RODENTIA FROM LEISEY SHELL PIT
B a;
D j a._,E
-p
I
Figure 5. Erethizon dorsatum, Leisey 3, left mandible with p4-m2, UF 124632. (A) lateral view; (B)
medial view, (C) dorsal view. Neochoerus sp., Leisey 3, left mandible with il, UF 124559. (D) lateral
view, (E) dorsal view. Scale bars for A and B (under B) and C (right of C) both 10 mm in length. Scale bar
for D and E (under D) 30 mm in length.
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, NO. 13
Table 5. Mandibular measurements (in nmm) of late Pliocene and Pleistocene Erethizon from Florida.
alveolar
length of depth of depth of length length
lower mandible mandible of of length width
species toothrow at p4 at m2 diastema symphysis p4 p4
Erethizon sp.
Haile 7C
UF 121740
Erethizon kleini
Inglis IA
UF 21473 (type)
UF 21474
UF 21475
Erethizon dorsatum
Haile 16A
UF 21490
UF 21492
Erethizon dorsatum
Leisey 3
UF 124632
UF 128200
UF 135669
Erethizon dorsatum
Apollo Beach
UF 24112
UF 24113
UF 24114
Erethizon dorsatum
Aucilla River
UF 92392
Erethizon dorsatum1
Recent (n=154)
mean
range
32.6 8.0 6.6
25.7 22.9 14.4 16.3 30.9 7.1 5.9
24.7 20.4 14.2 12.9 28.0 6.7 5.6
- 15.1 -
30.6 28.9 20.1 24.5 41.4 8.4 7.1
31.3 26.1 17.0
31.6 26.4 16.9
- 27.4 17.2
21.8 15.2
28.6 21.8 16.7
28.2 22.5 13.8 15.8 31.6 7.5 6.1
29.1 25.1 16.0 22.8 36.5 7.5
25.3- 20.1- 12.2- 17.3- 29.6- 6.0
33.1 30.2 18.9 27.9 44.4 9.0
Erethizon mandibles from Apollo Beach is generally similar to the three Leisey
specimens as well, further indicating an Irvingtonian age for at least a portion of
the Apollo Beach fauna. The late early Irvingtonian Haile 16A and Leisey Shell
Pit local faunas, and perhaps the Apollo Beach LF as well, appear to represent the
oldest records of E. dorsatum. The earliest previous records of E. dorsatum were
MORGAN & WHITE: RODENTIA FROM LEISEY SHELL PIT
Table 5 Extended.
length width length width length width
Species ml ml m2 m2 m3 m3
Erethizon sp.
Haile 7C
UF 121740
Erethizon kleini
Inglis IA
UF 21473 (type)
UF 21474
UF 21475
Erethizon dorsatum
Haile 16A
UF 21490
UF 21492
Erethizon dorsatum
Leisey 3
UF 124632
UF 128200
UF 135669
Erethizon dorsatum
Apollo Beach
UF 24112
UF 24113
UF 24114
Erethizon dorsatum
Aucilla River
UF 92392
Erethizon dorsatum1
Recent (n=154)
mean
range
7.5 6.5 7.4 7.1 6.7 6.0
7.0 6.7 7.1 7.0 7.5 6.7
7.1 6.4 7.3 6.9 -
5.6 5.2 5.9 6.1 6.2 5.7
- 6.4 -
5.3- -
- 7.9 -
I Meauumenmts from Frai (1981, Tble I).
from middle Irvingtonian faunas, including Cumberland Cave, Port Kennedy
Cave, Trout Cave, and Conard Fissure (Frazier 1981).
Since the publication of Frazier's (1981) review, fossils of Erethizon have
been recovered from three additional Florida sites, including the Leisey Shell Pit.
The other new sites represent the oldest and youngest well-documented records of
porcupines in Florida. An associated palate and mandible from the latest Blancan
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, NO. 13
Haile 7C LF (UF 121740) is the only Florida Blancan occurrence of Erethizon, and
the earliest record of the genus in eastern North America (Hulbert et al. 1989).
This specimen is much larger than E. kleini and somewhat larger than E. dorsatum
(Table 5). It is comparable in size to E. bathygnathum from the late Blancan and
early Irvingtonian of the western United States. The youngest porcupine fossil
from Florida is a complete mandible with full dentition (UF 92392) ofE. dorsatum
from the late Rancholabrean Aucilla River LF in Taylor County in the eastern
panhandle. The closest records of extant E. dorsatum are from southern Tennessee
to the north and central Texas to the west (Hall 1981).
Family HYDROCHAERIDAE Gill 1872
Neochoerus sp.
Referred Specimens.-Leisey 1A: UF 83244, 83828, 86942, II (3); UF
66101, 95881, il (2); UF 66102, 86149, partial m2 (2); UF 66104, proximal
radius; UF 65400, proximal ulna; UF 66103, 88374, 115736, proximal femur (3);
UF 87967, astragalus. Leisey 3: UF 124173, right mandible edentulouss); UF
124559, left mandible with il; UF 124560, symphysis of left mandible; UF
124561, partial ml; UF 124562, m2. MNI=4.
Description.-The capybara sample from Leisey primarily consists of
fragmentary teeth and partial postcranial elements that are not diagnostic below
the family level. However, two mandibles (UF 124559, UF 124173) from Leisey 3
are complete enough to permit an identification to genus. Ahear and Lance
(1980) and Ahearn (1981) described several important characters of the mandible
and dentition that reliably separate the extant genus of capybara, Hydrochaeris,
from the extinct giant capybara, Neochoerus. The spelling of Hydrochaeris used
here follows the recommendation of Husson (1978), although the spelling
Hydrochoerus is more common in the literature (e.g. Kurtdn and Anderson 1980;
Mones and Ojasti 1986). We follow the dental terminology for capybara teeth used
by Ahearn and Lance (1980).
The location of the masseteric fossa and extent of the masseteric ridge, which
forms a bony shelf on the lateral surface of the dentary for the insertion of the
masseter muscle, differ between the two genera. In Neochoerus, the anterior
extremity of the masseteric ridge terminates lateral to the third prism of the p4 and
the anterior portion of the masseteric fossa is opposite the posterior edge of p4.
The masseteric ridge extends farther anteriorly in Hydrochaeris to the level of the
first or second prism of p4, and the anteriormost extension of the masseteric fossa
is more anterior as well. Another character separating these two genera is the
external structure of the incisor enamel. Hydrochaeris has a weak groove on the
lower and upper incisors, but lacks distinctly ridged enamel. Neochoerus has a
MORGAN & WHITE: RODENTIA FROM LEISEY SHELL PIT
deep groove and strongly ridged enamel on both incisors. Neochoerus is also
generally larger than Hydrochaeris.
In characters of the masseteric ridge and fossa, as well as size, the two
hydrochaerid mandibles from Leisey are clearly referable to Neochoerus. In both
of these specimens, the masseteric ridge terminates opposite the alveolus for the
third prism of p4 and the masseteric fossa extends to the level of, or very slightly
anterior to, the posterior edge of p4 (see Figs. 5D-E). The two Leisey mandibles
are considerably larger than modem comparative specimens of adult Hydrochaeris
in the UF Mammalogy Collection, but are smaller than several Rancholabrean
mandibles of N. pinckneyi examined from Florida, including UF 9763 from the
Ichetucknee River in Columbia County and UF 23497 from Octopus Cave in Levy
County. All hydrochaerid incisor fragments from Leisey have a well developed
groove and at least some evidence of the longitudinal ridges characteristic of
Neochoerus, although in most specimens the ridges are not as well developed as in
the larger N. pinckneyi. One upper incisor fragment from Leisey (UF 83828) has
strongly ridged enamel.
Although the Leisey mandibles are confidently referred to Neochoerus, they
lack the diagnostic features to permit an identification to the species level. Two
species of Neochoerus have been identified from Florida, N. dichroplax from
several late Blancan faunas and N. pinckneyi from numerous late Rancholabrean
faunas (Ahearn and Lance 1980; Kurtdn and Anderson 1980; Ahearn 1981).
These two species are distinguished from one another and from other species of
Neochoerus, most of which are restricted to South America, by characters of the
dentition, primarily the M3 and p4. As noted above, the two most complete Leisey
Neochoerus mandibles lack cheekteeth. Several isolated cheekteeth are present in
the Leisey sample, but these are all fragmentary, and do not include the diagnostic
M3 or p4.
Neochoerus dichroplax is characterized by having split or bifurcated laminae
on the labial edge of M3. This species also can be separated from N. pinckneyi by
its relatively shorter p4 in which the connection between the first and second
prisms is reduced and the second labial fissure is directed between the second and
third prisms. Two capybara mandibles from the late Blancan Macasphalt Shell Pit
LF have complete p4s and the anterior portion of the masseteric ridge preserved, a
juvenile left mandible with p4-ml (UF 60858) and an adult right mandible with p4
(UF 94630). In both mandibles the masseteric ridge extends anteriorly opposite
the third prism of the p4, and in the adult specimen the incisor enamel is strongly
ridged as is typical of Neochoerus. The p4 in both specimens has the morphology
of N. dichroplax in which the connection between the first and second prisms is
reduced and the second labial fissure is directed between the second and third
prisms (Ahearn and Lance 1980).
Based on the two Leisey mandibles, as well as several partial M3s from the
apparently correlative Apollo Beach fauna, there may be a third species of
Neochoerus from Florida that occurred during the early Irvingtonian. This
427
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, NO. 13
capybara cannot be confidently separated from N. dichroplax based on the
available mandibles, but the M3s from Apollo Beach lack the characteristic
bifurcations of the Blancan species. The two edentulous mandibles of Neochoerus
from Leisey resemble the adult mandible of N. dichroplax from the Macasphalt
Shell Pit. However, the diagnostic occlusal pattern of the p4 cannot be accurately
determined from the empty alveoli in the Leisey mandibles. Mandibles of N.
pinckneyi are larger than those of Neochoerus from Leisey and N. dichroplax from
Macasphalt, and the p4 is considerably more elongated, a feature that can be
ascertained from the alveolus. Only more complete material of Irvingtonian
Neochoerus from Florida will permit a definite allocation to species. The
fragmentary Neochoerus teeth from Apollo Beach were referred to N. pinckneyi by
Ahearn (1981), but are here placed in Neochoerus sp. along with the Leisey
sample. The Leisey material is either referable to N. dichroplax or it represents a
new species, it is not conspecific with Rancholabrean N. pinckneyi.
Remarks.-Ahearn (1981) reviewed the fossil record of the Hydrochaeridae
in North America. She recognized three species of capybaras from late Pliocene
and Pleistocene sites in Florida: Neochoerus dichroplax from the late Blancan, N.
pinckneyi from the Irvingtonian and Rancholabrean, and Hydrochaeris holmesi
from the late Blancan through the Rancholabrean. Although hydrochaerids are
fairly common in Florida Blancan, Irvingtonian, and Rancholabrean faunas, they
are rare in other North American Plio-Pleistocene sites. Ahearn and Lance (1980)
described N. dichroplax from the late Blancan Dry Mountain and 111 Ranch
faunas in Arizona, with referred specimens from two late Blancan localities in
southwestern Florida, Sommer's Pit in Sarasota County and Mule Pen Quarry in
Collier County. Morgan and Ridgway (1987) have since reported N. dichroplax
from the late Blancan Macasphalt Shell Pit in Sarasota County. Morgan and
Hulbert (this volume) list hydrochaerids from several additional Florida late
Blancan local faunas, but this material is too fragmentary for a generic allocation.
Neochoerus was one of the first Neotropical immigrants to reach North America in
the late Pliocene (late Blancan) during the Great American Interchange. The late
Blancan Neochoerus from Arizona and Florida represent the earliest North
American records of capybaras (Ahearn and Lance 1980). The association of
Neochoerus with certain indigenous North American taxa, in particular Nannippus
peninsulatus, is characteristic of the late Blancan between about 2.5 and 2.0 Ma.
Pending discovery of more diagnostic material, the early Irvingtonian
Neochoerus from Florida cannot be identified to species. This capybara is either
conspecific with N. dichoplax, thereby extending the chronologic range of that
species into the early Irvingtonian, or it represents an undescribed form. Ahearn
(1981) gave the chronologic range of N. pinckneyi in Florida as middle or late
Irvingtonian through late Rancholabrean. She listed only two Irvingtonian sites
for this species, Santa Fe 2A and Apollo Beach. Further study indicates that the
Santa Fe 2A fauna is Rancholabrean, whereas the Apollo Beach Neochoerus is
MORGAN & WHITE: RODENTIA FROM LEISEY SHELL PIT
probably not referable to N. pinckneyi. The Apollo Beach fauna is a mixed
assemblage consisting of both Irvingtonian and Rancholabrean species. Many
mammals in the Apollo Beach fauna, including Castoroides sp., Erethizon
dorsatum, Arctodus pristinus, and Tapirus haysii, are similar to those from the
nearby Leisey Shell Pit and are probably early Irvingtonian in age. N. pinckneyi is
restricted to the Rancholabrean in Florida where it is fairly common, particularly
in sites that sample freshwater depositional environments such as streams, springs,
and lakes. Castoroides ohioensis and Tapirus veroensis are common faunal
associates ofN. pinckneyi in Florida late Rancholabrean riverine faunas.
A third and somewhat smaller species of extinct capybara, Hydrochaeris
holmesi, was described by Simpson (1928) from the late Rancholabrean Sabertooth
Cave LF in Citrus County, Florida. Subsequently H. holmesi has been reported
from numerous other Florida sites ranging in age from late Blancan to late
Rancholabrean (Kurt6n and Anderson 1980; Ahearn 1981). Pre-Rancholabrean
records of H. holmesi include the late Blancan Haile 15A LF, the earliest
Irvingtonian Inglis IA LF, and the late Irvingtonian Coleman 2A LF (Ahearn
1981).
There is some confusion regarding the generic identification of North
American fossil capybaras. Although most previous authors (e.g. Kurten and
Anderson 1980; Ahearn 1981) recognized two genera of fossil capybaras from
Florida, Hydrochaeris and Neochoerus, Mones and Ojasti (1986:1) stated that,
"References to fossil Hydrochoerus in North America...are misidentifications of
Neochoerus (Mones 1984)." Hydrochaeris holmesi was regarded as a synonym of
Neochoerus aesopi (=N. pinckneyi) by Mones (1984), although he did not provide
morphological descriptions or further justification for this taxonomic decision.
Until more thorough morphological comparisons are conducted, it seems most
prudent to continue recognition of H. holmesi.
Family MURIDAE Gray 1821
Subfamily SIGMODONTINAE Thomas 1897
Sigmodon libitinus Martin 1979
Referred Specimens.-Leisey 1A: UF 132070, partial right M2; UF 132071,
left M3. Leisey 3A: UF 124588, right maxilla with M1-M2; UF 124331, left
maxilla with MI; UF 124329, 124586, right mandible with ml-m2 (2); UF
124587, left mandible with ml-m2; UF 124325, right mandible with m2; UF
124314, right mandible with m3; UF 124310, 124313, 124319, 124320, 125210,
128965, 128966, 132057, right MI (8); UF 124312, 124326, 124589, 128967, left
MI (4); UF 124590, 125209, 128968, left M2 (3); UF 124315, 124322, 132058,
right M3 (3); UF 124321, 128971, 132059, right ml (3); UF 128972-128975,
132060, left ml (5); UF 124311, 124316, 124317, 128976, right m2 (4); UF
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, NO. 13
124318, right m3; UF 124323, 124324, 124327, 128977, 132061, left m3 (5).
Leisey 3B: UF 132054, edentulous left maxilla; UF 132055, right m3. MNI=11.
Description.-A species of the genus Sigmodon is the most abundant rodent
at Leisey where it is represented by more than 50 specimens of maxillae,
mandibles, and isolated teeth from a minimum of 11 individuals. Six species of
Sigmodon are now known from late Pliocene and Pleistocene sites in Florida. Four
of these species of cotton rats, S. curtisi, S. minor, S. libitinus, and S. bakeri, are
found in Irvingtonian faunas, while S. medius occurs only in late Blancan faunas
and S. hispidus is restricted to the Rancholabrean and Recent. The Leisey
Sigmodon were directly compared to Florida samples of all six of these species,
including: five mandibles of S. medius from the late Blancan Macasphalt Shell Pit
LF, 20 mandibles of S. curtisi from the earliest Irvingtonian Inglis lA LF, two
isolated teeth of S. minor from the earliest Irvingtonian De Soto Shell Pit LF in De
Soto County, 20 mandibles of S. libitinus from the early Irvingtonian Haile 16A,
12 mandibles of S. bakeri from the late Irvingtonian Coleman 2A LF, and a large
sample of modern S. hispidus from northern peninsular Florida.
Martin (1979) provided descriptions, diagnoses, and measurements for the
various extinct and living species of Sigmodon. Following Martin, most
comparisons and measurements of the species of Sigmodon are based on the lower
dentition. The most important morphological changes in Sigmodon occur on the
ml, with some characters on the m2 and m3 as well. The presence or absence of
small accessory roots on ml is an important character in the evolutionary history of
Sigmodon. The most primitive species, S. medius, generally possesses only the
primary anterior and posterior roots, and small accessory roots are lacking. Most
Irvingtonian species of Sigmodon, including S. curtisi and S. libitinus, have three
roots, including a small accessory labial root in addition to the two primary roots.
The more advanced species in the genus, including S. bakeri and S. hispidus, have
four roots on ml, the two primary roots and both a labial and a lingual accessory
root. Another important dental feature of the ml is the structure of the
anteroconid. The two Pliocene species, S. medius and S. curtisi, as well as S.
hispidus, tend to have symmetrical anteroconids on ml, whereas S. libitinus and S.
bakeri both have asymmetrical anteroconids resulting from a moderately to well
developed posterolabial extension.
The presence or absence of an anterior cingulid on m2 and m3 helps to
differentiate several species of Sigmodon. S. medius, S. curtisi, and S. hispidus
have anterior cingulids on m2 and m3, S. libitinus lacks these cingulids on most
but not all teeth, and S. bakeri completely lacks anterior cingulids. Size is also an
important diagnostic character used to separate the various species of Sigmodon.
S. medius and S. minor are both quite small, and in fact these two species are often
synonymized under S. minor. S. curtisi, S. libitinus, and S. bakeri are intermediate
in size, with S. curtisi slightly larger than the other two. S. hispidus is the largest
species of the genus in Florida. Measurements of the mandible and lower dentition
MORGAN & WHITE: RODENTIA FROM LEISEY SHELL PIT
of fossil and modern Sigmodon from Florida are presented in Table 6. Although
not extensive, the sample of lower molars of Sigmodon from Leisey is adequate for
relatively detailed comparisons with other extinct and living species of the genus
from Florida (Figs. 6A-B).
Sigmodon medius can easily be separated from the Leisey Sigmodon by its
smaller size, lack of accessory roots on ml, and lower crowned teeth. S. minor,
known from Florida only by two teeth from the De Soto Shell Pit, is so much
smaller than the Leisey Sigmodon that further comparisons are unnecessary. S.
curtisi from Inglis differs from the Leisey cotton rat in its larger size, much greater
frequency of anterior cingulids on m2 and m3, and nearly symmetrical anteroconid
on ml. S. baker can be separated from the Leisey Sigmodon by the presence of a
fourth lingual accessory root on ml and by the more prominent posterolabial
extension of the anteroconid. The extant cotton rat, S. hispidus, represents the
most advanced species of the genus, and can be distinguished from the Leisey
Sigmodon by its larger size, presence of two accessory roots on ml, presence of
well developed anterior cingulids on m2 and m3, and higher crowned teeth.
The Leisey Sigmodon compares quite well in most respects with the sample of
S. libitinus from Haile 16A, the type locality of this species (Martin 1979). The
Leisey sample is very similar in size to both S. libitinus and S. bakeri (Table 6).
Nine of ten mis from Leisey have three roots, including large anterior and
posterior roots and a much smaller labial accessory root. Only a single ml from
Leisey (UF 128974) has a tiny fourth lingual accessory root. Similarly, only two of
twenty mis (10%) of S. libitinus from Haile 16A possess the minuscule fourth
lingual accessory root. All Leisey mis have asymmetrical anteroconids, most of
which have small to moderately developed posterolabial extensions as in the Haile
16A sample. An anterior cingulid is absent from all seven m2s in the Leisey
sample and is present on only one of five m3s (UF 128977; Fig. 6B). However,
many of the lower molars from Leisey are well worn and the anterior cingulid is
generally only in evidence on unworn to lightly worn teeth. About half of the 20
mandibles of S. libitinus examined from Haile 16A have small to moderately well
developed anterior cingulids on m2 and m3.
The Leisey Sigmodon is very similar in size and most dental features to S.
libitinus, and is here confidently referred to that species. The only character in
which the Leisey Sigmodon differs from the type series of S. libitinus from Haile
16A is the higher incidence of anterior cingulids on m2 and m3 in the Haile 16A
sample. The rarity of anterior cingulids in the Leisey teeth is a character shared
with the late Irvingtonian species S. bakeri. This difference may indicate a slightly
younger age for Leisey compared to Haile 16A, but is not a significant enough
feature to warrant description of a new species.
In many respects, S. libitinus from Haile 16A and Leisey is intermediate
between S. curtisi from Inglis lA and S. bakeri from Coleman 2A. S. libitinus
agrees with S. curtisi in the possession of only three roots on ml, but is similar to
431
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, NO. 13
Table 6. Measuremets (in mm) of the mandible and lower dentition of fossil and Recent Sigmodon from
Florida. Mean, observed range, and sample size, respectively, are provided for each measurement.
Alveolar
Species, length of
Locality, mandibular length width length width length width
and Age toothrow ml ml m2 m2 m3 m3
Sigmodon curtisi
Inglis IA 6.62 2.37 1.65 1.76 1.86 2.28 1.76
earliest 6.33-6.78 2.20-2.51 1.56-1.75 1.65-1.82 1.75-2.00 2.03-2.45 1.66-1.85
Irvingtonian 10 10 10 10 10 7 7
Sigmodon libitinus
Haile 16A 6.19 2.26 1.54 1.60 1.71 2.12 1.65
late early 5.87-6.52 2.13-2.37 1.48-1.63 1.53-1.69 1.61-1.77 1.86-2.27 1.53-1.74
Irvingtonian 10 10 10 10 10 10 10
Sigmodon libitinus
Leisey Shell Pit 6.03 2.20 1.49 1.59 1.65 1.92 1.65
lateearly 5.93,6.12 2.04-2.32 1.42-1.56 1.51-1.65 1.56-1.71 1.80-2.01 1.52-1.77
Irvingtonian 2 8 9 7 7 3 3
Sigmodon baker 6.03 2.23 1.52 1.55 1.69 1.87 1.59
Coleman2A 5.80-6.35 2.05-2.53 1.46-1.58 1.46-1.68 1.60-1.81 1.84-1.90 1.51-1.70
late Irvingtonian 8 12 12 7 7 3 3
Sigmodon hispidus1
Reddick IA 7.27 2.49 1.73 1.82 2.02 2.59 1.88
late 6.83-7.65 2.24-2.72 1.63-1.86 1.67-1.95 1.88-2.14 2.24-3.00 1.77-1.96
Rancholabrean 18 18 18 18 18 18 18
Sigmodon hispidus1 7.26 2.47 1.65 1.77 1.97 2.56 1.91
Recent, Florida 6.56-7.80 2.11-2.73 1.55-1.88 1.59-1.96 1.79-2.13 2.17-2.89 1.77-2.10
30 30 30 30 30 30 30
SMesuurnents fon Mutin (1979, Tble I).
S. bakeri in size and in the asymmetrical structure of the anteroconid on ml. The
S. libitinus sample from Haile 16A is similar to S. curtisi in having small anterior
cingulids in about half of the lower m2s and m3s. The Leisey sample seems to be
more similar to S. bakeri in lacking the anterior cingulids in the majority of the
second and third lower molars. No anterior cingulid was observed in any
specimens of S. bakeri examined.
MORGAN & WHITE: RODENTIA FROM LEISEY SHELL PIT
C D
A
E F G
Figure 6. (A) Sigmodon libiinus, Leisey 3A, left ml-m2, UF 124587; (B) Sigmodon libitinus, Leisey 3A,
left m3, UF 128977.; (C) Podomys sp., Leisey 3A, left m2, UF 124332; (D) Ondatra annectens, Leisey 3,
left ml-m2, UF 125207; (E)Pedomys sp., Leisey 3A, right m2, UF 124334; (F) Pedomys sp., Leisey 3A,
right M3, UF 125170; (G)Pedomys sp., Leisey 3A, right M3, UF 125212. Both scale bars 1 mm in length,
shorter scale applies only to D, longer scale applies to A-C and E-G.
433
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, NO. 13
Sigmodon libitinus is also present in two other Florida early Irvingtonian
sites. A left mandible with ml-m3 (UF 91014) was collected by James Ranson
from the Shell Materials Pit located in Ruskin, Hillsborough County, only about 5
km north of Leisey. This specimen is very similar in size and other morphological
features to the S. libitinus sample from Leisey, with one exception. The nearly
unworn m2 and m3 of this mandible have small but readily discernible anterior
cingulids. A fourth sample of S. libitinus from the early Irvingtonian Payne Creek
Mine in Polk County consists of a maxilla with two teeth, a mandible with two
teeth, and seven isolated molars. The Payne Creek Sigmodon sample contains four
mis (UF 129026, 129028-129030) that are nearly identical to those from Leisey.
Three of these four teeth have three roots, while the fourth has a tiny fourth lingual
accessory root. All four Payne Creek mis have a rather well developed
posterolabial extension on the anteroconid. A nearly unworn m2 (UF 129031)
from Payne Creek has a tiny anterior cingulid that obviously would have
disappeared with only moderate wear. A well worn m2 and m3 in a mandible (UF
129032) lack any evidence of an anterior cingulid, as is typical of the Leisey
sample.
Remarks.-Cotton rats of the genus Sigmodon are usually the most abundant
small mammals in Florida Irvingtonian faunas. The various species of Sigmodon
in Florida apparently filled the ecological role of small grazing rodents that is
typically occupied by arvicolines in more temperate northern and western faunas
(Martin 1979). In his review of the evolutionary history of Sigmodon, Martin
(1979) noted that the replacement chronology of Sigmodon species in the Plio-
Pleistocene of Florida provides a very useful biochronological sequence.
Identification of a Sigmodon species from a Florida site permits chronologic
refinement to a portion of a NALMA. Whereas arvicoline rodents are generally
rare or absent in Florida Blancan and Irvingtonian sites, Sigmodon is usually
present if a site has any small mammals at all. Furthermore, it is not necessary to
have a large sample; a single mandible or even an isolated ml of Sigmodon may be
adequate for a species identification.
Six species of cotton rats are recorded from faunas in Florida starting in the
late Blancan and continuing until the present. The small, primitive species, S.
medius, occurs in two Florida late Blancan faunas, Haile 15A (Martin 1979) and
Macasphalt Shell Pit (Morgan and Ridgway 1987). S. medius is the characteristic
cotton rat of the Blancan NALMA. S. medius was originally described from the
Benson LF of Arizona, and has since been reported from numerous Blancan faunas
throughout the western United States (Kurt6n and Anderson 1980). S. medius is
unknown from faunas younger than late Blancan, unless this species is
synonymized with S. minor, in which case its chronological range extends into the
earliest Irvingtonian. S. minor is here reported from Florida for the first time in
the earliest Irvingtonian De Soto Shell Pit LF. The two teeth of S. minor from De
MORGAN & WHITE: RODENTIA FROM LEISEY SHELL PIT
Soto are much smaller than comparable teeth of S. medius from the older Haile
15A and Macasphalt Shell Pit local faunas.
The De Soto Shell Pit is the only Florida fossil site with two species of
Sigmodon, as S. curtisi occurs there as well. S. curtisi was first recorded in Florida
from the earliest Irvingtonian Inglis IA by Martin (1979). Western faunas
containing S. curtisi are the Curtis Ranch LF in Arizona (type locality) and the
correlative Vallecito Creek LF in California, as well as the slightly younger
Kentuck LF in Kansas (Martin 1979). Winkler and Grady (1990) also mentioned
the presence of S. curtisi in the Fyllan Cave LF in Texas, which may be as young
as middle Irvingtonian. S. libitinus previously was restricted to the type locality,
the early Irvingtonian Haile 16A LF (Martin 1979). S. libitinus is now known
from the Leisey Shell Pit, the Payne Creek Mine LF, and the Shell Materials Pit,
all of which are roughly correlative late early Irvingtonian faunas. S. bakeri was
described from the late Irvingtonian Coleman 2A LF (Martin 1974, 1979), and
also was reported from several Florida early Rancholabrean local faunas, including
Bradenton, Haile 7A, and Williston 3A. The extant cotton rat S. hispidus is the
typical species found in Florida late Rancholabrean faunas, although it first
appears in the early Rancholabrean Haile 8A and Daytona Beach local faunas.
Podomys sp.
Referred Specimen.-Leisey 3A: UF 124332, left m2. MNI=1.
Description.-A single well worn m2 is the only specimen of a peromyscine
rodent recovered from the Leisey Shell Pit LF (Fig. 6C). We follow Carleton's
(1980) classification in which he recognized many former subgenera of
Peromyscus, including Podomys, as full genera. The Leisey tooth agrees in
general morphological characters with modern species of peromyscines from
Florida, including the cotton mouse Peromyscus gossypinus and the Florida mouse
Podomysfloridanus. However, this tooth is far larger than Peromyscus gossypinus
and somewhat larger than Podomysfloridanus. The dimensions of the Leisey m2
are: length 1.74 mm, width 1.34 mm. Measurements of ten m2s of modern
Podomys floridanus from Alachua County, Florida are: length (mean=1.38,
range=1.34-1.43), width (mean=1.16, range=l.12-1.20). The large size of the
Leisey tooth is notable, as P. floridanus is one of the largest living species of
peromyscines in the United States.
Only two Irvingtonian species of Peromyscus (sensu lato) appear to be within
the size range of the large Leisey tooth, P. cumberlandensis and P. irvingtonensis.
P. cumberlandensis was originally described from the middle Irvingtonian
Cumberland Cave LF in western Maryland (Guilday and Handley 1967). This
species also has been reported from the middle Irvingtonian Trout Cave LF in
West Virginia and the Rancholabrean Ladds Quarry in northern Georgia (Ray
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, NO. 13
1967). Measurements of nine m2s of P. cumberlandensis from Cumberland Cave
are (from Guilday and Handley 1967): length (mean=1.7, range=1.6-1.8); width
(mean=1.4, range=1.3-1.5). The average size of the Cumberland Cave m2s is
almost exactly the same as the Leisey tooth. Guilday and Handley (1967)
described P. cumberlandensis as having a moderately complicated dental pattern
with relatively well developed mesolophids and mesostylids on the lower molars.
However, they also noted that the mesolophid and mesostylid were present in only
33% of the m2s in the Cumberland Cave sample. The Leisey tooth has a
comparatively simple dental pattern. A mesolophid is absent and the mesostylid
and ectostylid are present, but both cusps are very small, especially the mesostylid.
Because the mesolophid and mesostylid are present on only one-third of the P.
cumberlandensis m2s, the Leisey specimen cannot definitely be excluded from this
species, although it is unlikely that the two taxa are conspecific. Savage (1951)
described Peromyscus irvingtonensis based on a single mandible lacking m2 from
the type Irvington fauna in California. This large species is a member of the
primitive subgenus Haplomylomys, which is characterized by the absence of
accessory cusps on the molars. As noted above, the Leisey tooth has two very
small accessory cusps, a mesostylid and ectostylid.
A third, large extinct species of Peromyscus, P. oklahomensis, occurs in two
early Rancholabrean faunas, the Doby Springs LF from Oklahoma and the Easley
Ranch LF in Texas. The type specimen of P. oklahomensis from Doby Springs is
an m2. The measurements of this tooth are: length 1.7 and width, 1.3, exactly the
same dimensions as the Leisey m2. Furthermore, P. oklahomensis was described
as having a simple dental pattern resembling that of the slightly smaller Florida
mouse, Podomys floridanus. However, based on the diagnosis and figure
(Stephens 1960), P. oklahomensis differs in several characters from the Leisey
tooth, including the very broad reentrant valleys between the major cusps, a well
developed mesostylid, and reduced ectostylid. In the Leisey specimen, the cusps
are separated by rather narrow re-entrant valleys and the ectostylid is larger than
the mesostylid, although both cusps are rudimentary.
It appears likely that the Leisey peromyscine m2 represents a large,
undescribed species of Podomys. However, a single worn tooth is inadequate for
the description of a new species. No morphological characters other than larger
size clearly distinguish the Leisey m2 from modern comparative specimens of
Podomys floridanus from peninsular Florida. In a sample of ten m2s of P.
floridanus, a mesolophid is absent from all ten teeth, six teeth have a small
mesostylid, and eight have a small ectostylid. The Leisey m2 lacks a mesolophid
and bears a small mesostylid and ectostylid.
Undescribed specimens of large peromyscines are present in other Florida
Irvingtonian faunas. A nearly complete mandible with ml-m3 from the early
Irvingtonian Haile 21A LF (UF 62638) is larger than P. floridanus, but the m2 is
smaller than the Leisey tooth (measurements: length 1.61, width 1.27).
Furthermore, the Haile 21A m2 has a small mesolophid, a character that is absent
MORGAN & WHITE: RODENTIA FROM LEISEY SHELL PIT
in P. floridanus and the Leisey specimen. An upper M2 of a large peromyscine
from the early Irvingtonian Payne Creek Mine LF (UF 129023) cannot be directly
compared to the Leisey tooth, but was compared to the extant P.floridanus sample.
The Payne Creek tooth has a well developed mesoloph, a feature lacking in P.
floridanus. The best sample of large peromyscines from the Florida Irvingtonian is
found in the Haile 16A LF. Detailed analysis of this sample is beyond the scope of
the present study; however, a preliminary examination suggests that the large Haile
16A peromyscine has a simple dental pattern and is probably referable to Podomys.
The Haile 16A and Leisey Podomys are very similar, if not conspecific.
Subfamily ARVICOLINAE Gray 1821
Ondatra annectens (Brown 1908)
Referred Specimen.--Leisey 3: UF 125207, left mandible with il, ml-m2.
MNI=I.
Description.--A single well preserved mandible with a partial incisor and
complete ml and m2 is the only specimen of Ondatra recovered from the Leisey
Shell Pit (Fig. 6D). The presence of Ondatra in the Leisey fauna is certainly
fortuitous, as the evolutionary history of the muskrat lineage is perhaps better
known than that of any other rodent in the Plio-Pleistocene of North America
(Semken 1966; Nelson and Semken 1970; Martin and Tedesco 1976). The
morphological characters used to distinguish the various species in the lineage
consist primarily of features evident on the ml, including size (length and width),
number of triangles, complexity of the anteroconid, amount of cement in the
reentrant angles, and height of the dentine tracts. The only one of these characters
not readily observable in the Leisey mandible is the height of the dentine tracts on
ml, as both teeth are firmly implanted in the mandible. However, some of the
dentine tracts on ml reach the occlusal surface of the tooth and this, taken in
conjunction with the wear stage, does provide a good approximation of dentine
tract height.
Measurements of the total length and maximum width of the occlusal surface
of ml are presented in Table 7 for five samples of Ondatra from Florida: O.
idahoensis from the earliest Irvingtonian Inglis 1A and De Soto Shell Pit local
faunas, 0. annectens from the early Irvingtonian Leisey Shell Pit and Payne Creek
Mine local faunas, and 0. zibethicus from the late Rancholabrean Ichetucknee
River LF. Two of these sites, De Soto and Leisey, are represented by a single
specimen. The sample of 0. idahoensis from Inglis IA is one of the largest known
for this species, including 20 mandibles, 12 of which have an ml. The Payne
Creek sample of 0. annectens includes three complete mis, as well as eight
additional isolated teeth. The four Florida Irvingtonian samples fit rather well into
the two typical late Pliocene and early Pleistocene species of Ondatra described
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, NO. 13
from western North America, 0. idahoensis from the late Blancan and earliest
Irvingtonian and the somewhat larger 0. annectens from the late early and middle
Irvingtonian.
The measurements of the Ondatra ml from the Leisey Shell Pit and three
mis from Payne Creek Mine (Table 7) are within the size range of 0. annectens
(Nelson and Semken 1970). Comparison with the oft-cited figure in Nelson and
Semken (1970, fig. 1), which shows the ratio of length to width in the ml of the
classic Blancan through Rancholabrean Ondatra samples from North America,
demonstrates that the Leisey and Payne Creek Mine Ondatra falls well within the
range of 0. annectens from the early Irvingtonian Java LF from South Dakota and
Kentuck LF from Kansas and the middle Irvingtonian Cudahy LF in Kansas.
Twelve mis of Ondatra from Inglis 1A and one ml from the De Soto Shell Pit are
notably smaller than mis from Leisey and Payne Creek (Table 7). The Inglis and
De Soto Ondatra compare well in length with samples of 0. idahoensis from the
late Blancan Grandview LF in Idaho and White Rock LF in Kansas. However, the
Florida 0. idahoensis are narrower than western specimens of similar age,
averaging less than 2.0 mm, while all of the western 0. idahoenis samples average
greater than 2.0 mm in width (ranging from 2.1-2.4 mm). A sample of 23 mis of
0. zibethicus from the late Rancholabrean Ichetucknee River LF in Columbia
County (Table 7) is considerably larger than 0. annectens.
Ondatra annectens has five to seven closed triangles on the ml. The
presence of five triangles is a primitive feature in the muskrat lineage and is typical
of all species prior to 0. annectens, including 0. idahoensis, while 0. zibethicus
usually has seven or more closed triangles. The Leisey ml has six closed triangles
on ml, as well as a broadly open, rudimentary seventh triangle. All three mis
from the Payne Creek Mine have only five closed triangles, but small open sixth
and seventh triangles are present. The pattern of enamel triangles on the ml from
these two sites is actually very similar. The only difference is that in the Leisey ml
the fourth lingual reentrant extends almost entirely across the tooth and nearly
contacts the fourth labial reentrant, thereby isolating a sixth triangle. The fourth
lingual reentrant in the Payne Creek sample does not extend as far labially, and
thus the sixth triangle, although well developed, is not closed. In a sample of O.
annectens from the Java LF (Martin 1989), unworn mis may have as many as
seven well separated triangles, while deeply worn specimens usually have only five
closed triangles with rudimentary sixth and seventh triangles, as in the Payne
Creek 0. annectens.
The mis of Ondatra annectens from Leisey and Payne Creek have five
lingual and four well developed labial reentrants, whereas 0. idahoensis typically
possesses five lingual, but only three large labial reentrants. In the ml from De
Soto Shell Pit and most of the specimens from Inglis IA there are also one to two
tiny labial reentrants on the anteroconid. The larger and more posterior of these
MORGAN & WHITE: RODENTIA FROM LEISEY SHELL PIT
Table 7. Measurements (in mm) of the ml of fossil Ondatra from Florida. Mean, observed range, and
sample size, respectively, are provided for the samples from Inglis IA, Payne Creek Mine, and Ichetucknee
River.
length width
Species and Locality ml ml
Ondatra idahoensis
Inglis IA 4.5 1.9
(4.2-4.8) (1.7-2.1)
N=12 N=10
Ondatra idahoensis
De Soto Shell Pit
UF 125222 4.6 1.9
Ondatra annectens
Leisey Shell Pit
UF 125207 5.6 2.5
Ondatra annectens
Payne Creek Mine 5.8 2.5
(5.5-6.0) (2.4-2.6)
N=3 N=3
Ondatra zibethicus
Ichetucknee River 7.7 2.9
(7.3-8.3) (2.6-3.2)
N=23 N=23
two rudimentary reentrants is probably homologous with the prominent fourth
labial reentrant of 0. annectens.
When comparing teeth of similar wear stage, the dentine tracts are much
better developed and extend higher on the ml in Ondatra annectens from Leisey
and Payne Creek than in 0. idahoensis from De Soto and Inglis. On the Leisey
ml, the dentine tracts extend to the occlusal surface on the lingual and labial
termination of all triangles except one, as well as on the posterior loop. The Leisey
tooth is moderately worn, but not extremely so. The dentine tracts in the three mis
from Payne Creek are similar in their development to the Leisey specimen. In a
deeply worn ml from Payne Creek all dentine tracts reach the occlusal surface,
whereas in a lightly worn tooth only about half of the dentine tracts intersect the
tooth crown. In the third Payne Creek tooth all but one of the labial and lingual
reentrants reach the occlusal surface, just as in the Leisey specimen. The dentine
tracts are not nearly so well developed in the 0. idahoensis sample from Inglis and
De Soto. Not a single dentine tract reaches the occlusal surface in the De Soto
tooth, while in the Inglis IA sample the dentine tracts fail to reach the occlusal
surface in seven mis. On the remaining five teeth, most of which are more heavily
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. II, NO. 13
worn, a single dentine tract located at the labial termination of the posterior loop
extends to the tooth crown.
Both Ondatra annectens and 0. idahoensis are characterized by the presence
of cement in the reentrant angles; however, the cement is much better developed in
the former species. From one-half to three-fourths the width of the reentrant
angles is filled with cement in the Leisey and Payne Creek 0. annectens mis.
Although cement is present in all reentrant angles of the ml in the two Florida O.
idahoensis samples, it often consists of a thin layer, generally filling less than one-
fourth the width of the reentrant.
The anterior half of a lightly worn ml (UF 11455) from the Pool Branch LF
in Polk County constitutes a third record of Ondatra annectens from Florida. The
fourth lingual reentrant in the Pool Branch ml extends almost entirely across the
tooth, but does not quite contact the fourth labial reentrant, and thus the sixth
triangle is not completely closed. Dentine tracts reach the occlusal surface at the
labial and lingual termination of four of the five triangles preserved, and cement
fills about three-fourths the breadth of the reentrant angles. Although incomplete,
the Ondatra ml from Pool Branch is similar in size and dental characters to O
annectens from Leisey and the nearby Payne Creek Mine.
Remarks.-The phyletic lineage of North American muskrats has been
variously interpreted as containing six species in two genera (from oldest to
youngest: Pliopotamys minor-P. meadensis-Ondatra idahoensis-O. annectens-O.
nebracensis-0. zibethicus) to consisting of a single continuously evolving lineage
placed in the extant species Ondatra zibethicus (Martin 1993). Early and middle
Blancan faunas and the muskrats typical of this time period, the two species of
Pliopotamys, are unknown from Florida. However, three of the four species of
Ondatra known from Irvingtonian and Rancholabrean faunas have been identified
from Florida. Only 0. nebracensis is unrecorded from the state.
Species of Ondatra are excellent biochronological indicators in Irvingtonian
and Rancholabrean faunas throughout North America (Nelson and Semken 1970;
Martin and Tedesco 1976). Ondatra is uncommon in Florida late Pliocene and
Pleistocene vertebrate faunas, but when present provides a good indication of the
age of a site. The oldest arvicoline rodent known from Florida is 0. idahoensis
from the latest Pliocene Inglis 1A and De Soto Shell Pit local faunas. Frazier
(1981) first noted the presence of 0. idahoensis at Inglis 1A. The Inglis muskrat
was previously reported as 0. zibethicus (Webb 1974). Numerous other
mammalian taxa in common between Inglis and De Soto indicate that these faunas
are earliest Irvingtonian in age. 0. idahoensis also occurs in the earliest
Irvingtonian Curtis Ranch LF in Arizona (Irvingtonian I of Repenning 1987), as
well as slightly older late Blancan faunas (Blancan V of Repenning 1987),
including Borchers and White Rock in Kansas, Mullen and Seneca in Nebraska,
and Grand View in Idaho (type locality).
440
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