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Group Title: Bulletin of the Florida Museum of Natural History
Title: Revision of the extinct pseudoceratinae
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Title: Revision of the extinct pseudoceratinae (Artiodactyla: Ruminantia: Gelocidae)
Physical Description: p. 17-58 : ill. ; 28 cm.
Language: English
Creator: Webb, S. David ( Sawney David ), 1936-
Publisher: Florida Museum of Natural History, University of Florida
Place of Publication: Gainesville, FL
Gainesville, FL
Publication Date: 2008
Copyright Date: 2008
 Subjects
Subject: Artiodactyla, Fossil -- Florida -- Withlacoochee River   ( lcsh )
Mammals, Fossil -- Florida -- Withlacoochee River   ( lcsh )
Paleontology -- Florida -- Withlacoochee River -- Miocene   ( lcsh )
Paleontology -- Florida -- Withlacoochee River -- Pliocene   ( lcsh )
Genre: bibliography   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Abstract: The Pseudoceratinae is a North American clade of small, hornless ruminant artiodactyls known from the late middle Miocene to the earliest Pliocene. Two genera and three species are recognized: Pseudoceras skinneri Frick 1937 (including P. potteri Frick 1937 and P. wilsoni Frick 1937 as junior synonyms); Floridameryx floridanus new genus and species; and Floridameryx klausi (Frick 1937), new combination. Originally regarded as small, aberrant members of the Camelidae, cranial (especially basicranial), dental, and post cranial characters clearly place the Pseudoceratinae instead within the artiodactyl suborder Ruminantia, and more precisely within the extinct family Gelocidae. Among the derived ruminant (pecoran) character states exhibited by the pseudoceratines, the following are most notable: broad postglenoid process; fully developed odontoid process of axis; lack of upper incisors; forelimb length nearly equal to that of hindlimb; third and fourth metacarpals and metatarsals fully fused into cannon bones with well developed distal keels; metatarsal with deep, distally bridged anterior groove; fused cuboid and navicular; and parallel-sided astragalus. Floridameryx differs from Pseudoceras by having a wider skull with weaker parietal and sagittal crest, reduced premolars, higher crowned molars, and shorter metatarsals. The Withlacoochee River 4A locality in north-central Florida produces the largest population sample of pseudoceratines, with a minimum of 26 individuals represented, and is the only known site to have a pseudoceratine as the most common ungulate. About half of the mandibles bear small, procumbent, incisiform canines, as it typical in advanced ruminants, while the other half have large, upright canines which occluded with the upper canines. This is interpreted as sexual dimorphism, with the former morphology presumably representing females and the latter males. The abundance of pseudoceratineates in the Withlacoochee 4A fauna, seen in its paleoecological context, is attributed to a preference for very mesic, densely forested environments.
Statement of Responsibility: S. David Webb.
Bibliography: Includes bibliographical references (P. 55-57).
General Note: Cover title.
General Note: Bulletin of the Florida Museum of Natural History ; vol. 48, no. 2, pp. 17-58
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Bibliographic ID: UF00101265
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
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Resource Identifier: oclc - 248636605
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Table of Contents
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        Front Cover
    Front Matter
        Front Matter
    Main
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--FLORIDA
MUSEUMW
OF NATURAL HISTORYTM


BULLETIN


REVISION OF THE EXTINCT PSEUDOCERATINAE
(ARTIODACTYLA: RUMINANTIA: GELOCIDAE)


S. David Webb











Vol. 48, No. 2, pp. 17-58


2008


UNIVERSITY OF FLORIDA


GAINESVILLE







The FLORIDA MUSEUM OF NATURAL HISTORY is Florida's state museum of natural history, dedicated to
understanding, preserving, and interpreting biological diversity and cultural heritage.

The BULLETIN OF THE FLORIDA MUSEUM OF NATURAL HISTORY is a peer-reviewed publication
that publishes the results of original research in zoology, botany, paleontology, and archaeology. Address all inquiries
to the Managing Editor of the Bulletin. Numbers of the Bulletin are published at irregular intervals. Specific volumes
are not necessarily completed in any one year. The end of a volume will be noted at the foot of the first page of the
last issue in that volume.



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ISSN: 0071-6154

Publication Date: June 25, 2008






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REVISION OF THE EXTINCT PSEUDOCERATINAE
(ARTIODACTYLA: RUMINANTIA: GELOCIDAE)





S. David Webb






ABSTRACT

The Pseudoceratinae is a North American clade of small, hornless ruminant artiodactyls known from the late middle Miocene to the earliest
Pliocene. Two genera and three species are recognized: Pseudoceras skinneri Frick 1937 (including P. potter Frick 1937 andP. wilsoni Frick
1937 as junior synonyms); Floridameryx floridanus new genus and species; and Floridameryx klausi (Frick 1937), new combination.
Originally regarded as small, aberrant members of the Camelidae, cranial (especially basicranial), dental, and postcranial characters clearly
place the Pseudoceratinae instead within the artiodactyl suborder Ruminantia, and more precisely within the extinct family Gelocidae.
Among the derived ruminant (pecoran) character states exhibited by the pseudoceratines, the following are most notable: broad postglenoid
process; fully developed odontoid process of axis; lack of upper incisors; forelimb length nearly equal to that of hindlimb; third and fourth
metacarpals and metatarsals fully fused into cannon bones with well developed distal keels; metatarsal with deep, distally bridged anterior
groove; fused cuboid and navicular; and parallel-sided astragalus. Floridameryx differs from Pseudoceras by having a wider skull with
weaker parietal and sagittal crests, reduced premolars, higher crowned molars, and shorter metatarsals.
The Withlacoochee River 4A locality in north-central Florida produces the largest population sample of pseudoceratines, with a
minimum of 26 individuals represented, and is the only known site to have a pseudoceratine as the most common ungulate. About half of the
mandibles bear small, procumbent, incisiform canines, as is typical in advanced ruminants, while the other half have large, upright canines
which occluded with the upper canines. This is interpreted as sexual dimorphism, with the former morphology presumably representing
females and the latter males. The abundance of pseudoceratinates in the Withlacoochee 4A fauna, seen in its paleoecological context, is
attributed to a preference for very mesic, densely forested environments.


Key Words: Pseudoceras, Ruminantia, Gelocidae, osteology, Miocene, Florida, Hemphillian



TABLE OF CONTENTS

Introduction .................................................................................. ................ 18
System atic P aleontology..................................... ..... .................. ................ 19
G enus Pseudoceras ....... .... .... .. ............ ..... ............................ 19
G enus F loridam eryx ............................................................ ................... 20
O steology of the Pseudoceratinae................................................ .................. 22
G general Features of the Skull.................................................. .................. 22
Restoration of the Withlacoochee Floridameryx Cranium.......................... 23
C ran iu m ......................................................................................................... 2 3
U p p er D en titio n ...................................................................... ................ 3 5
L ow er D en tuition ........................................... ... .................... ................ 37
A xial Skeleton ........................... ............................................................. . 4 1
F o re lim b ......................................................................................................... 4 2
H in d L im b ........................................................... .................... .. . ............ 4 5
L ocom otorA daptations ........................................................... .................. 47
R elation ship s ......................................................................... . . ............ 4 8
C on clu sio n s........................................................................................................ 54
A ckn ow ledgem ents ............................................... .... .................... ................ 54
L literature C ited ............................................................ ................. .. . ........... 5 5
A p p en d ix I.......................................................................................................... 5 8


'Distinguished Research Curator Emeritus, Florida Museum of Natural History, University of Florida, Gainesville, FL 32611-7800, USA.

Webb, S.D. 2008. Revision of the Extinct Pseudoceratinae (Artiodactyla: Ruminantia: Gelocidae). Bull. Florida Museum Nat. Hist. 48(2): 17-58.







INTRODUCTION
In May 1967, scuba-diving paleontologists from the
Florida Museum of Natural History discovered a rich
concentration of bones representing a new genus and
species of the extinct subfamily Pseudoceratinae in
sediments beneath the Withlacoochee River in central
Florida. This new pseudoceratine was the most common
species at the site, known as Withlacoochee River 4A
(at ca. 280 59' N; 820 21' W). Seven seasons of
underwater collecting produced about 700 specimens
representing at least 26 individuals of the new taxon
and nearly all of its skeleton, including many elements
previously unknown in any pseudoceratine.
In the original description, Frick (1937) assigned
the Pseudoceratinae to the Camelidae. Simpson (1945)
followed this assignment, but with a query. The new
Florida sample shows clearly that the Pseudoceratinae
belong with the hornless Ruminantia rather than with
the Camelidae. An intriguing irony accompanies Frick's
original assignment. Although he relegated
Pseudoceratinae to an appendix under the rubric of
Camelidae (Frick 1937:648-652), the volume in which
they were presented was his great tome "Horned
Ruminants of North America". Perhaps Frick and his
assistants knew subconsciously that they were dealing
with ruminants after all, albeit ones without horns.
The primary basis for Frick's assignment of
Pseudoceratinae to Camelidae was the upright lower
canine tooth, evident in the holotype mandible of
Pseudoceras skinneri. In the Withlacoochee River
4A sample, however, this feature occurs in 12 of the 22
complete mature rami; in the other 10 rami the lower
canine tooth is smaller and incisiform as in typical
Ruminantia (In many of these mandibles the actual
canine is absent, but its size and orientation can be
inferred from the alveolus). The new sample
demonstrates that the nature of the lower canine cannot
be used absolutely as a criterion distinguishing Camelidae
from Ruminantia. In this instance it would lead to the
absurdity of dividing an otherwise unified population into
Camelidae and Ruminantia. The differences in lower
canine morphology are instead interpreted to be sexual
dimorphism.
It was evident to the author as early as 1970 that
the Withlacoochee River 4A sample of Pseudoceratinae
had important implications for the phylogeny of hornless
ruminants. It took another decade and two trips to
Europe to pursue those implications. Taylor and Webb
(1976) and Webb and Taylor (1980) were both attempts
to penetrate some of the mysteries of lower ruminant
phylogeny.


BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(2)

Based on their findings Webb and Taylor (1980:154)
asserted that Pseudoceras was a North American
gelocid. Tedfordetal. (1987:189; 2004:216-217) likewise
recognized Pseudoceras as an immigrant gelocid, and
McKenna and Bell (1997) classified it within the
Gelocidae. A gelocid origin for Pseudoceras was also
noted by Webb (1998) in a review article on the fossil
homeless ruminants of North America. The morphologic
evidence for this relationship is formally presented here
for the first time.
The following review of the Pseudoceratinae
consists of three parts. First is a systematic revision of
the extinct subfamily, taking into account undescribed
fossil collections from Florida and elsewhere in North
America. The second section provides an osteological
description of the subfamily based primarily on the rich
sample from Withlacoochee River 4A. And the third
part features relationships, tracing the evolution of
Pseudoceratinae back to their probable origins among
lower Pecora in the Oligocene and Miocene of Eurasia.

ABBREVIATIONS AND DEFINITIONS
This paper is based primarily on fossils catalogued
in the vertebrate paleontology collection of the Florida
Museum of Natural History, University of Florida,
Gainesville (abbreviated as UF). Other relevant
paleontological collections and their abbreviations are:
MCZ, Museum of Comparative Zoology, Harvard
University, Cambridge, Massachusetts; F:AM, Frick
Collection, American Museum of Natural History, New
York; TMM, Texas Memorial Museum, University of
Texas, Austin; and UNSM, Nebraska State Museum,
University of Nebraska, Lincoln.
All measurements are given in millimeters (mm).
Standard abbreviations of I for incisor, C for canine, P
for premolar, and M for molar are used; a preceding D
indicates a deciduous tooth; and the following numeral
the relative tooth position (M2 = upper second molar).
Upper case letters denote upper teeth; whereas lower
case letters refer to mandibular teeth. n denotes sample
size; s, sample standard deviation; and x, sample mean.
Definitions and boundaries of North American
Land Mammal Ages and biochronology of North
American fossil localities follow Tedford et al. (2004),
with the exception of McGehee Farm, which is regarded
as earliest Hemphillian (Hhl) as in Tedford et al. (1987)
for the reasons outlined by Hulbert and Whitmore (2006).
Following Tedford et al. (2004), Cl denotes the
Clarendonian Land Mammal Age and Hh the
Hemphillian; numbers following these abbreviations
signify a subage, e.g., C13 equates to the late
Clarendonian.





Webb, S.D.: Revision of the Extinct Pseudoceratinae


SYSTEMATIC PALEONTOLOGY
Order ARTIODACTYLA Owen 1848
Suborder RUMINANTIA Scopoli 1777
Family GELOCIDAE Schlosser 1886
Subfamily PSEUDOCERATINAE Frick 1937
Included Genera.-Pseudoceras Frick 1937 and
Floridameryx, new genus.
Diagnosis.-Diminutive hornless ruminants. Skulls
oftraguloid proportions, sharing many gelocid features.
Dental formula 10/3, C 1/1, P 3/3, M 3/3. Lower incisors
procumbent and spatulate; lower canines upright and
occluding with upper canines in presumed males,
procumbent and incisiform in presumed females; short
diastemata; p absent; p2-p4 with weakly developed
lingual cuspids as in Gelocidae,tending to posterolingually
oriented metaconid and transverse compression as in
Bachitherium; length of premolar series relatively
shorter than in most Gelocidae, ranging from 55 to 70
percent of molar series; molars with gelocid pattern,
crenulated enamel, numerous cingula and stylids,
mesodont to incipiently hypsodont, and transversely
compressed. Cementum often present in contrast with
Gelocus. Postcranial skeleton broadly comparable to
that of Moschus, with forelimbs nearly equal in length
to hindlimbs. Astragalus parallel-sided and cubic in
proportions. Metapodials fused into cannon bones with
complete distal keels. Metatarsus with distally enclosed
anterior gutter, unlike Moschus.
Distribution.-Late middle Miocene to early
Pliocene of North and Central America (Clarendonian
and Hemphillian Land Mammal Ages).

Genus Pseudoceras Frick 1937
Type Species.-Pseudoceras skinneri Frick
1937.
Distribution.-Late middle Miocene to late
Miocene of High Plains, Gulf Coastal Plain, and Central
America (Cll to Hh2).
Generic Diagnosis.-Skull narrower than in
Floridameryx, with stronger parietal and sagittal crests,
longer occipital overhang, and bulla broadly appressed
against basioccipital. Length of premolar series about
65 to 70 percent of molar series. Molars mesodont and
not markedly compressed. Metatarsus about ten percent
longer than that of Floridameryx floridanus.
Etymology.-Pseudo, Gr., false; ceras (or keras),
Gr., horn (neuter); in reference to the false resemblance
to homed ruminants or to Protoceratidae.
Included Species.-The type species only (see
below).


Pseudoceras skinneri Frick 1937
Pseudoceras wilsoni Frick 1937:651.
Pseudoceras potteri Frick 1937:652.
Blastomeryx elegans Matthew and Cook 1909, Patton
(1969), in part, Texas specimens only.
Holotype.-F:AM 33723, left mandibular ramus
with i3, c, p2-m3.
Type Locality.-East Kat Quarry, Cherry County,
Nebraska.
Discussion.-The holotypes and referred
specimens of Pseudoceras wilsoni and Pseudoceras
potteri came from the same stratigraphic unit (Merritt
Dam Member of Ash Hollow Formation) and the same
region of Nebraska as the holotype of Pseudoceras
skinneri and are here regarded as synonyms of P.
skinneri. Supposed differences among the three noted
by Frick (1937), such as postcanine diastema length,
represent ordinary variation within the same species, as
demonstrated in the larger pseudoceratine sample from
Withlacoochee River 4A. An important specimen, only
briefly mentioned by Frick (1937:243, 651), is F:AM
33720, a nearly complete skull from Hans Johnson
Quarry, there tentatively referred to Pseudoceras.
Another series of specimens from the Merritt Dam
Member in northern Nebraska are present in the
University of Nebraska Collection and were briefly
mentioned by Frick (1937:649). The best example is
UNSM 26606, a left mandible collected by F. Walker
Johnson from the Platybelodon barnumbrowni locality
on the east side of Snake River.
An additional pair of mandibles (evidently of one
individual) from Cherry County are F:AM 53365 and
53368. These come from Clayton Quarry (Burge level),
and thus document the earliest records of Pseudoceras
skinneri in the Cll (Tedford et al. 2004).
The youngest records (Hh2) of P skinneri come
from FT-40 and FT-49, the Amebelodon fricki sites in
northern Nebraska where a series of dentaries, UNSM
46059-46063, compare closely with the C13 samples.
In four mature lower dentitions premolar length averages
20.5 mm and molar lengths average 29 mm, giving a
ratio of about 0.68. Leite (1990) recorded another
specimen of similar faunal age from the Lemoyne local
fauna in Keith County, Nebraska.
Evidently the earliest accession of a diagnostic
specimen of Pseudoceras skinneri was made by
Alexander Agassiz in October 1882. Agassiz had
received a shipment of specimens from Charles H.
Stemberg including the right mandible of a small ruminant
from Prairie Dog Creek near Logan, Phillips County,
Kansas. Agassiz catalogued it as MCZ 3313 and







identified it (in ink) as Blastomeryx scotti. The six cheek
teeth clearly represent P skinneri, with the premolar
series measuring 20.4 and the molars 31.7 in length.
In the southern Great Plains the best sample of
Pseudoceras skinneri comes from the C13 Higgins
Locality in Lipscomb County, Panhandle of Texas. This
population appears to have significantly larger body size
than the northern plains samples of similar age. The
clearest evidence comes from three adult metatarsals,
F:AM 95232, 95234 and 95237, that average 128 mm in
length, about eight percent larger than the northern
Nebraska metatarsals. Conceivably this sample
deserves recognition as a larger species; on the other
hand, it seems preferable to regard the size difference
as clinal variation within the same species, a pattern
documented in other Clarendonian ungulates (Webb
1969a).
On the Gulf Coastal Plain of Texas, the C12 Lapara
Creek Fauna includes at least one clear record of
Pseudoceras skinneri. A right mandible, TMM 30896-
496 from Buckner Ranch in Bee County, was referred
by Patton (1969) to Blastomeryx elegans but the
premolars are diagnostic of Pseudoceras. If one
includes the alveoli for p2, the length of the little-worn
premolar series measures 22 mm, and that of the molar
series is 31 mm, thus falling within the range of the
northern Nebraska series of P skinneri. The two other
small ruminant specimens cited by Patton (1969)
probably also represent Pseudoceratinae.
Hulbert and Whitmore (2006) recorded
Pseudoceras sp., based on an astragalus, at the Hh2
Mauvilla local fauna in Alabama. However, with the
proposed recognition of two genera ofpseudoceratines
in this work, the very limited Mauvilla sample is now
only diagnostic to the subfamily level.
Pseudoceras skinneri also occurs in the Love
Bone Bed, Alachua County, Florida, another C13 record
(Webb et al. 1981). A diagnostic example is a complete
metatarsal, UF 25007, with a length of 119.5, which
compares very closely with specimens from Nebraska.
Additional specimens include UF 24990, ml; UF 24999,
three isolated molars; UF 25000, two fused thoracic
vertebrae; UF 25001, a scapula; UF 25002, two humeri;
UF 25003, two radii; UF 25004, a complete metacarpus;
UF 25005, six metacarpal fragments; UF 25006, a distal
end ofatibia; UF 25008, four astragali; and UF 25009,
three phalanges.
The range of Pseudoceras skinneri extends south
into Honduras where it occurs in the Hh2 fauna from
the Gracias Formation. There Webb and Perrigo (1984)
reported ten specimens, and illustrated UF 18041, a right


BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(2)

mandibular ramus with m2-m3. These teeth measure
slightly larger than the equivalent teeth in the type
specimen from Nebraska.

Floridameryx n. gen.
Type Species.-Floridameryx floridanus, new
species.
Included Species.-Floridameryx klausi (Frick
1937), new combination.
Distribution.-Late Miocene of New Mexico (C12)
and late Miocene to earliest Pliocene of Florida (Hhl-
Hh4).
Generic Diagnosis.-Skull wider than in
Pseudoceras, with weaker parietal and sagittal crests,
no occipital overhang, and bulla separated by a gap from
basioccipital. Length of premolar series about 55
percent of molar series. Molars incipiently hypsodont,
with modest cementum, and tending to transverse
compression. Metatarsals about ten percent shorterthan
in Pseudoceras.
Etymology.-Florida, honoring the state; meryx (or
meryco), Gr., masculine sheep, or, more generally,
ruminant.

Floridameryx floridanus n. sp.
Pseudoceras sp., Webb (1998), in part; Tedford et al.
(2004:207); Webb et al. (2008).
Pseudoceras n. sp., Hulbert and Webb (2001:269-270;
fig. 13.39).
Holotype.-UF 13832, male left ramus with cl,
p2-p4, ml-m3 in little-worn condition, from
Withlacoochee River 4A, Marion-Citrus county line,
Florida, collected by UF field parties led by N. Tessman
in 1968.
Allotype.-UF 19395, female left ramus with il,
p2-4, ml-m3 in little-worn condition, from Withlacoochee
River 4A, collected by S. D. Webb and H. Converse in
1970. The use of an allotype instead of a paratype in
this case emphasizes the systematic importance of sexual
dimorphism in this species.
Known Distribution.-Late Miocene to earliest
Pliocene of Florida (Hhl-Hh4).
Referred specimens.-The extensive sample of
material from the type locality is listed in the Appendix.
Several other sites in Florida also produce material
referable to this species. Haile 6A: UF 2181, ml; and
UF 25436, a medial phalanx. McGehee Farm Site: UF
11002, a metacarpus; and UF 25437, an astragalus. Both
of these sites are in western Alachua County and are
early Hemphillian (Hh 1) in age, thus slightly older than





Webb, S.D.: Revision of the Extinct Pseudoceratinae


the Hh2 type locality (Hulbert 2005; Hulbert & Whitmore
2006).
The Hh4 Palmetto Fauna, previously recognized
as the classic "Bone Valley Fauna" of Polk County, also
includes Floridameryx floridanus (Webb et al. 2008:
therein listed as "Pseudoceras sp."), the youngest
definitive records of the subfamily. Perhaps the most
diagnostic specimen is a complete metatarsus, UF
133997, from the Whidden Creek local fauna.
Measuring 105.5 mm in length, it falls neatly within the
size range of the Withlacoochee River 4A sample, and
is about ten percent shorter than metatarsi of
Pseudoceras skinneri. Other Palmetto Fauna
specimens are listed in Webb et al. (2008).
Diagnosis.-Smaller than Pseudoceras skinneri.
Differs from Floridameryx klausi by having incipiently
hypsodont molars and lower molars with flattened lingual
walls strongly compressed in transverse dimensions.
Short premolars, metaconid long with flat lingual wall.
Lower premolar series averages 15 mm long; lower
molar series about 28 mm long. Mean unworn metaconid
height of m3 8.8 mm; mean length, 13.0 mm; mean width,
4.5 mm.
Etymology.- "Floridian". This species name
honors the special kind of paleontological wealth that
Florida often provides. The richest sample of
pseudoceratines by far comes from the Withlacoochee
River 4A site which also gives a special insight into the
paleoecology of this species.
Discussion.-The large sample of Floridameryx
floridanus from Withlacoochee River 4A forms the
principal basis for the osteology (below). The
Withlacoochee River 4A local fauna is late early
Hemphillian (Hh2) in age (Becker 1985; Tedford et al.
1987,2004). The minimum number of individuals, based
on the proximal end of left metatarsals, is 26, but surely
many more contributed to the large sample.
The setting in which Floridameryx floridanus
occurs so abundantly consists of a freshwater pond or
oxbow lake cut deeply into the surrounding Eocene
limestone, now exposed in the bottom of the
Withlacoochee River. The vertebrate remains were
scattered through massive green clays and occasionally
concentrated in thin beds of silt. The composition of
this local fauna suggests an unusual paleontological
community. Many common species at Withlacoochee
4A are exceedingly rare or unknown elsewhere, and
conversely, species that are abundant in most
Hemphillian faunas are rare or absent. When present,
pseudoceratines are typically a very rare component of
North American ungulate faunas, but F floridanus is


by far the most common species found at Withlacoochee
River 4A. As is typical of early Hemphillian faunas in
Florida, equids are very diverse (8 species), but
Withlacoochee River 4A is the only site where
Hipparion cf. tehonense and the diminutive Nannippus
morgani are common (28% and 9% of identifiable teeth,
respectively) (Hulbert 1988, 1993). The most common
carnivore is the diminutive borophagine canid,
Borophagus orc (Webb 1969b), an appropriate-sized
predator to have hunted F floridanus and N morgani.
Larger mammals at this site include Thinobadistes,
Pliometanastes, Enhydritherium, Indarctos,
Machairodus, Cormohipparion, Protohippus,
Amebelodon, Aphelops, Teleoceras, Tapirus, and
Aepycamelus (Webb 1969; Wolff 1977; Becker 1985;
Hulbert 1988, 1993, 2005). The vertebrate fauna also
includes several perciform fishes, numerous amphibians,
various freshwater turtles and snakes, Alligator, several
sizes of tortoises, and an extinct egret, Egrc it, i ",yl,1 ',
(Becker 1985). The probable habitat adjacent to the
freshwater pond where material accumulated was
subtropical deciduous forest (a Florida "hammock").
Evidently this was the preferred habitat of Floridameryx
floridanus.

Floridameryx klausi (Frick 1937), new combination
Pseudoceras klausi Frick 1937:652; Galusha and Blick
(1971:109).
Pseudoceras sp., Tedford et al. (2004:200).
Holotype.-F:AM 31997, right ramus with p2 roots,
and p3-m3 in medium wear, from Round Mountain
Quarry, Chamita Formation, Santa Fe County, New
Mexico.
Known Distribution.-Late Miocene (C12) ofNew
Mexico.
Referred Specimens.-Two figured mandibles and
thirteen other rami and partial rami as cited in Frick
(1937:652). The two upper dentitions, there questionably
referred, also represent Floridameryx klausi.
Diagnosis.-Differs from Floridameryx
floridanus by having mesodont molars; lower molars
with partly flattened lingual walls and less compressed
in transverse dimensions. Short premolars, metaconid
not as long or as flattened as in Floridameryx
floridanus. Lower premolar series about 16 mm long;
lower molar series about 28 mm long. Unworn m3
metaconid height about 7.5 mm; mean length, 12.6 mm;
mean width, 5.2 mm.
Discussion.-Floridameryx klausi closely
resembles Floridameryx floridanus in size and
premolar reduction but is less progressive in a number







of dental features. The crown height of m3 in the slightly
worn type mandible is 7.4 mm; and that tooth in even
earlier wear in F:AM 33782 measures 7.5 mm high.
Comparable measurements in eight specimens of F.
floridanus ranged from 8.4 to 9.5 with a mean of 8.8.
Thus, F klausi had not attained the degree ofhypsodonty
that occurs in F floridanus.
A related distinction is the degree to which the
lower molars are transversely compressed. At the widest
point, the mean width of m3s of Floridameryx klausi
measures 5.2 mm. Although the m3s of F floridanus
are slightly longer than those of F klausi, their mean
width is 4.5 mm, nearly four standard deviations (0.21)
less than in F klausi. Similar comparisons between
maximum widths of the second lower molars yield 5.1
in F klausi and 4.6 in F floridanus, a difference of
nearly three standard deviations. Thus, in transverse
compression as in hypsodonty, F klausi molars are less
progressive than those of F floridanus.
The entire known sample of Floridameryx klausi
was collected by Frick Laboratory parties from the
Round Mountain Quarry near San Ildefonso, New
Mexico. That quarry produces excellent samples of a
limited variety of taxa. Although the quarry is isolated
from the continuous stratigraphic sections studied by
Galusha and Blick (1971), the fauna is regarded as
middle Clarendonian (C12) in age on biochronologic
grounds (Tedford et al. 2004).
If Floridameryx klausi is indeed middle
Clarendonian in age, it lived about four million years
earlier than Floridameryxfloridanus. The differences
between these two species consist of relatively minor
differences that would be expected as progressions in a
single evolving lineage. On the other hand, those changes
took place at a sufficiently rapid rate, and the gap in the
known record is sufficiently large, to permit a reliable
specific distinction.
During their brief span the Pseudoceratinae
diversified modestly. The earliest records from the early
Clarendonian in northern Nebraska (Burge Fauna) are
slightly smaller and more brachydont than typical
Pseudoceras skinneri from the late Clarendonian, thus
representing a plausible ancestral condition for all
subsequent North American pseudoceratines. This
species survived with few changes, other than a modest
increase in hypsodonty, through the late early
Hemphillian.
Floridameryx diverged from Pseudoceras as its
cranial proportions broadened and its premolar series
(and face) were abbreviated. During its recorded history
Floridameryx increased in hypsodonty at about the
same rate as Pseudoceras. Its size increased only


BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(2)

moderately so that it remained smaller than Pseudoceras
skinneri. Floridameryx first appears in the middle
Clarendonian as F klausi from Round Mountain quarry
in New Mexico. Its subsequent records (as presently
known) are confined to Florida. By late early
Hemphillian time, when the large sample of
Floridameryx floridanus was preserved at
Withlacoochee River 4A, this genus showed further
increases in the degree of hypsodonty and in the
transverse compression of its molars, but had made no
fundamental new departures. The latest Hemphillian
samples from the Palmetto Fauna reveal no significant
changes from the much better late early Hemphillian
samples.
Confinement of Floridameryx to one site in New
Mexico and a few sites in Florida suggests a very limited
(largely peripheral) geographic range. By contrast
Pseudoceras occurs widely through the midcontinent
and southward (through unknown ranges) to Honduras.
Neither genus seems to have ranged into or west of the
Rocky Mountain Province.

OSTEOLOGY OF THE PSEUDOCERATINAE
The following descriptive osteology is based primarily
on the rich sample of Floridameryx floridanus from
the Withlacoochee River 4A site in Florida (see
Appendix). The major exceptions are cranial features
taken from the previously undescribed skull of
Pseudoceras skinneri, F:AM 33720 from Hans
Johnson Quarry in northern Nebraska. Unless
otherwise stated, all comments refer to the UF sample
of F floridanus.
As the subsequent section on Relationships will
suggest, the Pseudoceratinae represent a branch of the
extinct family Gelocidae. Nonetheless, in many parts
of the following description comparisons are made with
more distantly related ruminant taxa, especiallyMoschus
and Tragulus, for the simple reason that these living
genera are better known and more widely available as
standards of comparison. I have added some descriptive
details regarding Gelocus to supplement that available
in the literature and to facilitate comparison with the
Pseudoceratinae. The phylogenetic significance of
many osteological features will be interpreted in the
section on Relationships.

GENERAL FEATURES OF THE SKULL
The skulls of Pseudoceratinae generally resemble
those of other hornless ruminants. Among living forms,
the relevant comparisons are with Tragulidae and
Moschidae. The small size, absence of frontal





Webb, S.D.: Revision of the Extinct Pseudoceratinae


appendages, large orbits near the mid-length of the skull,
short rostrum, and enlarged upper canines all suggest at
once that the heritage of Pseudoceratinae lies among
the primitive ruminants.
The size range of pseudoceratine crania falls
between Hyemoschus and Moschus. No
pseudoceratine is as small as the various species of
Tragulus nor small members of the extinct
Hypertragulidae such as Hypisodus. On the other hand,
no known Pseudoceratinae attain the size of the large
extinct tragulids Dorcatherium and Dorcabune. Thus,
the size range of the Pseudoceratinae lies near the mode
for primitive ruminants.
The absence of horns or antlers in Pseudoceratinae
is confirmed in five crania, one of Pseudoceras
skinneri and four of Floridameryx floridanus (Fig.
1). Large upper canines occur consistently, as in other
hornless ruminants, including Tragulidae,
Hypertragulidae, Gelocidae, and Moschidae.
Presumably sabre-like upper canines served as weapons
of defense in all of these groups that lack horns, antlers
or other frontal appendages.
Pseudoceratinae have the primitive ruminant
proportions with a short face on a relatively longer
braincase. More than a century ago Kowalevsky (1876)
and Rutimeyer (1883) observed that the braincase
(including orbits) is longer than the facial portion of the
skull in Tragulidae, Gelocidae, and other primitive
ruminants. The orbits are relatively large, while the
zygomatic processes of thejugal, squamosal, and frontal
bones are very slender. The anterior root of the
zygomatic arch is set low, just above the molar roots,
and the masseteric crest is weak. A lacrimal vacuity
separates the maxillary from the frontal bone and also
the lacrimal from the nasal bone, in the same relationship
that is found in Hypertragulidae, Gelocidae, and
Moschidae, but not in any of the Tragulidae.
The cranial vault is only moderately inflated, about
as in living Tragulidae. The parietal, sagittal, and mastoid
crests are even stronger than in living members of that
family and much stronger than in higher ruminants. In
general, the crests resemble those in Hypertragulidae.
The parietal crests form a triangular posterior skull table
with postorbital apices, emphasized by strong postorbital
constrictions. The basicranium is much wider than in
Tragulidae. The bullae are somewhat more inflated than
in Moschidae, about as in most Hypertragulidae; they
do not approach the degree of inflation found in
Tragulidae. The bullae are hollow, not cancellous as in
Camelidae. The glenoid fossa is broad with a broad
postglenoid process and crest, closely resembling the


condition in Gelocidae, Moschidae and higher ruminants.
The facial portion of the skull is flexed downward on
the braincase, more than in Tragulidae, about as in
Moschidae, but not to the extent seen in most homed
ruminants.

RESTORATION OF THE WITHLACOOCHEE FLORIDAMERYX
CRANIUM
Before proceeding to a detailed description of the
cranium, it is necessary to comment on the restoration
of the specimen shown in Figure 1. Despite the excellent
sample of Floridameryx floridanus from
Withlacoochee River 4A, some cranial features remain
in doubt. The "hinge region" between the braincase
and the facial region was restored almost in its entirety;
and the pterygoids, lacrimals, and nasals are virtually
unknown. While most features of the braincase and
orbitotemporal region are well represented in UF 13834,
it is an adolescent specimen, in which cranial flexion
may be exaggerated, and some dimensions are smaller
than in fully adult specimens. The dimensions, as
restored, were derived from two less complete but
mature specimens, namely UF 19257, an excellent
braincase lacking the orbital and sphenoid regions, and
UF 19258, an interorbital-frontal portion of a cranium.
The upper jaws and palate of the Withlacoochee
skull (Fig. 1) were restored using UF 13836 and 13833,
right and left premaxillary-maxillary series, respectively.
Slight differences in wear indicate that these represent
different individuals. The width of the palate across the
molars was determined partly from UF 19265, a maxillary
with well-worn teeth, in which the distance from the
midline to the labial wall of M3 was just over 18 mm.
Further concordant estimates were derived from the
occlusal relationships between the upper and lower
canines and from the contact between the incisive
processes in UF 13836 and 13833.
The restoration of the nasal and lacrimal bones is
largely hypothetical (Fig. 1D-E). The posterior
overlapping suture of the nasals on the frontals is clearly
demonstrated in two crania, UF 13834 and 19258. The
position of the posterolateral comer of the lacrimal is
presumably marked by the supraorbital notch as in most
other selenodont artiodactyls. The width of the nasals
anteriorly is constrained by the preserved dorsal portions
of the premaxillary and maxillary in UF 13836 and 13833.
The most uncertain aspect ofthis cranial restoration
was the relationship between the facial portion of the
skull and the braincase. A solution was provided by the
relationship between the glenoid fossa and the cheek
tooth row, which was determined from the large sample






BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(2)


5 cm


b cm


I





Webb, S.D.: Revision of the Extinct Pseudoceratinae


Figure 1. Composite cranium of Floridameryxfloridanus new genus and species, from the Withlacoochee River
4A Site, Florida. It is made up of UF 13834 (braincase, frontals, and orbits), 13833 (left premaxilla and maxilla), and
13838 (right premaxilla and maxilla); other regions reconstructed. The three specimens are most likely from three
different individuals. A, right lateral (reversed), B, ventral, and C, dorsal views of the cranium. D, lateral, and E,
dorsal views of an idealized reconstruction of the skull, showing sutures between major skull elements.


of undistorted mature mandibles. When this relationship
was satisfied, several other relationships across the
"hinge region" were concordant. These included the
outline of the orbit which is nearly circular, the zygomatic
arch as a nearly horizontal surface, the projection of the
palate across the pterygoid region to the base of the
alisphenoid, and the congruence of the frontal profile
with the nasal projection along the upper edge of the
maxillary. Because these relationships were satisfied


in well-preserved specimens, restored features such as
cranial flexion and cranial length must be constrained
within the normal range of mature specimens of
Floridameryx floridanus.

PREMAXILLA
In the Pseudoceratinae, each premaxilla consists
of an obliquely ascending facial portion and a horizontal
palatal portion (Fig. 1). The long, narrow facial portion







curves upward around the narial opening. The aperture
thus formed is somewhat taller than wide, about as in
Moschus and not so deep as in higher ruminants.
Although the upper edge in available specimens is broken,
the premaxilla evidently contacted the nasal bone broadly,
unlike Hyemoschus where the maxillary bone
intervenes, or Cephalophus where it only touches the
nasal. In lateral view, the posterior margin along the
maxillary follows a gentle sigmoid curve, convex dorsally
and concave ventrally near the canine. The suture
consists of a thin lamella of the premaxilla clasped
between inner and outer layers of the maxilla. This
tongue-in-groove structure, characteristic of all
ruminants, evidently enables the premaxillary-maxillary
junction to withstand considerable stress on the incisive
region. The premaxilla has no direct contact with the
canine alveolus as it often does in Moschus.
The palatal portion of the premaxilla is well-
preserved and shows clearly that no upper incisors were
present (Fig. 1B). It is somewhat longer than in
Tragulidae and is not so strongly downturned. On the
other hand, the incisive region is much shorter than in
Moschus, or especially than in any higher ruminant. The
vertical height ofthe premaxilla diminishes in the incisive
region, but it does not become flattened and broadened
as in Moschus and especially in higher ruminants. On
the contrary, the bone anterolateral to the incisive
foramen is deeper than it is wide. Presumably the horny
cropping pad had not developed to such an important
degree as in more advanced ruminants, especially in
grazers. The palatal exposure of the premaxilla is
unusually limited. The palatine processes, which join
together in the midline, are frail and short. Likewise the
incisive foramina, most of which they enclose, are only
about 10 mm long. With respect to these short, narrow
premaxillae, the Pseudoceratinae more nearly resemble
the Tragulidae and Cephalophus than even such
primitive ruminants as Moschus and Dremotherium.

MAXILLA
The maxilla covers much of the facial region and
most of the palate and supports the entire upper dentition.
The anterior tip of the palatal portion forms the
posterolateral margin ofthe incisive foramen in the usual
manner. The large upper canine is completely and firmly
surrounded by the maxillary bone (Fig. 1). The anterior
border of the facial portion, which is sutured to the
premaxilla, ascends obliquely to meet the nasal bone.
The root of the canine curves posterodorsallyjust within
the upper margin of the maxilla. The anterior end of
the infraorbital canal opens 6 mm above the P3. It


BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(2)

occupies the same position in the skull of Pseudoceras
skinneri as in one juvenile and seven adult specimens
of Floridameryx floridanus. This contrasts with the
usual position of the infraorbital foramen above and often
anterior to the P2 in most other ruminants, including
Moschidae and Tragulidae. The rest of the facial portion
of the maxillary is plain, marked only by a gentle
horizontal convexity above the molars, and a weak facial
crest extending forward from the jugal bone onto the
posterior edge of the maxilla. This posterior facial portion
of the maxilla is surprisingly shallow in view of the
considerable hypsodonty of the molars. The depth from
the jugal suture to the alveolar border of the M3 ranges
from 5.5 to 6.5 mm in mature specimens ofF.floridanus.
The alveolar border of the maxilla follows a gently
convex course curving ventrally and labially. The weakly
developed maxillary tuberosity projects posteromedially
behind the molars. The palatine suture crosses the
midline opposite Ml and turns posteriad adjacent to the
posterior molars. The anterior palatine foramen emerges
at the maxillo-palatine suture rather than within the
palatine as it does in Tragulidae. In Moschus and the
Cervidae, the position of this foramen is even farther
anterior, lying entirely within the maxilla, as noted by
Rutimeyer(1883). The forward passage of the palatine
nerves and arteries are marked by short but deep grooves
on the palatal surface ofthe maxillary bone. The palatine
portion of the maxilla is noticeably arched dorsally and
widens posteriorly adjacent to the palatine. Aprominent
diastematal crest curves lingually between the canine
and the premolars. This crest is stronger than in
Tragulidae and more closely approaches the midline, thus
resembling Moschidae and higher ruminants.

NASAL
The nasals are inadequately preserved in
pseudoceratine crania; only their posterior contact with
the frontals need be described. Each nasal forms a V-
shaped dentate suture with the frontal, the posteriormost
point lying lateral to the midline. The lateral edge of
each nasal lies about 2 mm medial to the course of the
supraorbital canal. The nasal is separated from the
lacrimal by the frontal bone and by a lacrimal vacuity.

LACRIMAL
The lacrimal bone is fully preserved only in the
skull of Pseudoceras skinneri, F:AM 33720. It forms
a broad plate on the side ofthe face immediately anterior
to the orbit, and it occupies an almost equal area inside
the orbit. The facial portion of the lacrimal is large and
flat as in Moschidae and Tragulidae. In many





Webb, S.D.: Revision of the Extinct Pseudoceratinae


artiodactyls and in most higher ruminants, by contrast,
this area is deeply depressed for a facial gland. A large
lacrimal vacuity is present, whereas in Tragulidae it is
absent. The vacuity is preserved only in Pseudoceras
skinneri. In Floridameryx floridanus the vacuity is
clearly indicated by the smoothly finished anterolateral
margins of the frontals. The vacuity, underlain by the
ethmoturbinal bones, has about the same width as the
facial exposure of the lacrimal bone. Its long dimension
extends anteroventrally as in most ruminants. In the
skull of P skinneri the upper margin of the lacrimal
bone, along the frontal suture, measures 9 mm, while
the ventral margin, along the maxilla and jugal, is about
13 mm long. A lacrimal fossa for the lacrimal duct lies
just inside the orbit and leads into a single anteriorly
directed foramen, as in Moschus.

FRONTAL
The frontal contributes more to the skull roof than
any other bone (Fig. 1). It does not reach posteriorly to
the orbit as in most homed ruminants, thus resembling
Moschus and Tragulidae. Presumably the posterior
extension of the frontal in higher ruminants is correlated
with the development of antlers and horns from that
bone.
The anterior, W-shaped contact with the nasals
lies well in front of the orbit. In Pseudoceras skinneri,
F:AM 33720, the frontals reach even farther forward
than the lacrimal, about 20 mm ahead of the orbit. In
Floridameryxfloridanus crania they extend only about
15 mm anterior to the orbit. In three specimens the
midline penetration of the nasals between the frontals is
only about 3 or 4 mm, whereas inMoschus the depth is
about 10 mm in most specimens. The lateral margin of
the frontal extends posterolaterally forming the upper
wall of the lacrimal vacuity; there it turns posteriorly
along the dentate suture with the lacrimal bone and
enters the anterodorsal comer of the orbit.
The frontal does not extend onto the side of the
face below the upper rim of the orbit as it does in most
higher ruminants. In this respect, the Pseudoceratinae
resemble Moschus. The frontal contributes a major
part of the inner wall of the orbit. The orbital walls are
not in such close contact as in Tragulidae or in
Cephalophus. Rather they are well separated in
Pseudoceras skinneri, closely resembling Moschus in
this respect; the walls are even more widely separated
in Floridameryx crania.
Inside the orbit the frontal slopes steeply in a
medioventral direction. It narrows toward its ventral
edge and forms a U-shaped contact with the pterygoid


and alisphenoid. The ethmoidal foramen lies anteriorto
its normal position in higher ruminants, almost touching
the lacrimal.
The dorsal exposure of the frontals is dominated
by a strong dome-like convexity much like that in
Moschus. Each supraorbital foramen is large, often
complexly subdivided, and leads forward into a deep
longitudinal groove. A small median foramen occurs
near the anterior end of the frontals in some specimens.
The postorbital process of each frontal is at least 7 mm
thick near its dorsal origin and descends nearly 15 mm
to its suture with the jugal.

JUGAL
This fragile bone is completely preserved only in
the skull of Pseudoceras skinneri, F:AM 33720. The
largest portion of the jugal contributes to the floor of the
orbit. Posteriorly it bifurcates in the usual manner to
produce an ascending postorbital process and a
horizontal zygomatic process.
The large suborbital portion of the jugal forms a
nearly horizontal plate about 12 mm wide that rises gently
toward the lacrimal bone in front of the orbit. From its
ventral surface this plate gives origin to the masseter
muscle, a strong masseteric crest marking the lateral
edge. The masseteric plate is only about 2 mm thick.
The anteriormost part of the jugal extends 5.8 mm in
front of the orbit along a nearly horizontal contact with
the lacrimal bone. In lateral view this antorbital portion
of the jugal remains rather shallow, not exceeding 8 mm
in depth.
Within the orbit, the jugal contact lies only about 1
mm below the lacrimal foramen. The anterolateral
contact with the maxillary is by a dentate suture, but
medially, against the alveolar region of the maxillary,
the contact follows a linear course. The maxillary
extends a long splint-like process posteriorly along the
ventro-medial edge of the jugal to a point posterior to
the postorbital bar.
The postorbital process of the jugal rises dorsally
and slightly anteriad, whereas in most ruminants and
tragulids the postorbital bar slopes posteriorly. The
contact between the frontal and jugal lies in the lower
third of the orbital opening as in Moschidae and Cervidae
generally, not in the upper third as in Tragulidae. The
zygomatic process of the jugal underlies the squamosal
and tapers to a point opposite the anterior edge of the
glenoid fossa. The masseteric crest follows this process
and continues as a strong crest onto the glenoid portion
of the squamosal as in Moschus and most ruminants.









PALATINE
The palatal exposure of the palatine extends from
the M2 to a point about 15 mm behind the M3. The
apex of the internal nares lies opposite the posterior edge
of the M3 as inMoschus and higher ruminants generally.
In Tragulidae, by contrast, the palatines meet at the
midline for nearly their full length and, as noted by
Rutimeyer (1881), the nares open behind the orbits. The
anterior palatine foramen borders the anterior margin
of the palatine, whereas in Tragulidae this foramen opens
wholly within the palatine.
The orbital exposure of the palatine rises to nearly
the middle of the orbit. It contacts the alveolar portion
of the maxilla laterally and makes an extensive
intraorbital contact with the frontal. The posterior
opening of the large infraorbital canal lies low on the
medial side of the alveolar region between the maxillary
and palatine bones as inMoschus and higher ruminants,
whereas in Tragulidae it lies directly above the alveolar
region, dorsolateral to its position in other ruminants. In
Tragulidae, the palatine bone extends laterally above the
maxillary to the infraorbital canal, whereas in
Pseudoceratinae, Moschus, and higher ruminants the
lacrimal bone occupies that position. The sphenopalatine
foramen is relatively small and low, as in higher
ruminants, and in strong contrast to the situation in
Tragulidae. The posterior palatine foramen opens in
the normal position below the sphenopalatine foramen.

PTERYGOID
This bone is preserved only as a minute piece in
the skull of Pseudoceras skinneri. Nonetheless traces
of its attachments to the medial wall of the alisphenoid,
and to the palatine, presphenoid, and basisphenoid, may
be recognized. It evidently occupied a trapezoidal area
on the medial wall of the pterygoid region, reinforcing
the alisphenoid-palatine connection. The pterygoid thus
resembles that of Moschus; it is not so reduced as in
Hyemoschus nor so strongly reflected as in Tragulus.

VOMER
The vomer is represented only by traces of its
contact with the presphenoid. Evidently the posterior
portion is weak and does not extend far posteriorly.

PRESPHENOID
At its posterior end the presphenoid is subcircular
in cross-section. In the middle portion, where it is
covered by the vomer, it becomes transversely


BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(2)

compressed; and at the anterior end it broadens again
to buttress the ethmoid region.

ORBITOSPHENOID
The ventral and anteroventral portions of this bone
are fused tightly onto the sides of the presphenoid. The
orbitosphenoid occupies the posteroventral part of the
orbital inner wall, posterior to the palatine. The contact
between the orbitosphenoid and frontal bones follows a
sigmoid course, rising from the midorbital region toward
the postorbital bar. The orbitosphenoid broadly contacts
the parietal in the posterior part of the orbital wall, much
as in Moschus, and not as in Tragulidae where the
alisphenoid intervenes. The posteroventral wall of the
orbitosphenoid borders the alisphenoid. The left and
right orbitosphenoids are widely separated across the
midline except at their bases. This contrasts with the
Tragulidae in which these bones are fused at the midline.
The optic foramen pierces the ventral wall of each
orbitosphenoid midway between the anterior and
posterior margins. The optic foramen also partly
excavates the posterodorsal surface of the presphenoid
just anterior to the optic chiasma.

ALISPHENOID
The alisphenoid borders the anterolateral edge of
the basisphenoid and extends wings or processes in three
different directions. One wing extends posteriorly under
the bulla; one ascends into the orbitotemporal region;
and the third passes anteroventrally as the pterygoid
process. The pterygoid process of the alisphenoid joins
the palatine to form the posterolateral edge of the hard
palate. In UF 19257 and 13834, suture scars indicate
the position of the small pterygoid bones on the medial
wall of the alisphenoids.
From the pterygoid portion of the alisphenoid an
unusually strong crest extends posteriorly along the edge
of the basisphenoid to connect with the anteromedial
wall of the auditory bulla. This crest forms the medial
wall of a channel for the eustachian tube and the tensor
tympani muscle. A much shorter and lower longitudinal
ridge on the alisphenoid forms the lateral wall of the
eustachian canal. The large foramen ovale lies
dorsolateral to the eustachian canal and occupies much
of the width of the posterior wing of the alisphenoid.
The foramen ovale faces ventrolaterally and slightly
anteriorly. Anterior to this foramen and at the base of
the pterygoid process are one or two moderate-sized
foramina for the subsphenoidal veins. Similar foramina
are common but variable in Moschus and Cervidae. A
narrow bridge of the alisphenoid (only about 3 mm wide),





Webb, S.D.: Revision of the Extinct Pseudoceratinae


separates the pterygoid wing of the alisphenoid from
the ascending wing. It faces anteroventrally and is taller
than wide (about 6 mm x 4 mm). The anterodorsal wall
of the foramen is formed by the orbitosphenoid bone.
The ascending portion of the alisphenoid contacts
the orbitosphenoid in the posteroventral comer of the
orbital chamber, but only for a short distance (about 9
mm). As in Moschus and higher ruminants, the
alisphenoid gives way dorsally to the parietal which
occupies the upper postorbital region. A strong
prominence for the lateral pterygoid muscle occupies
the area lateral to the sphenoidal fissure and a crest
passes posteriorly from it onto the squamosal as in most
ruminants. From the tip of this crest, the alisphenoid-
squamosal suture passes posteromedioventrally into the
tympanic region. The ascending wing of the alisphenoid
(covering the lateral wall of the braincase) is smaller
than its posterior wing (covering the ventral wall of the
braincase).

PARIETAL
The parietal occupies a greater portion of the
braincase than in higher ruminants, in which the frontal
is more expanded. In this respect Pseudoceratinae
resemble other hornless ruminants including the
Gelocidae, Moschidae, Hypertragulidae, and Tragulidae.
Likewise, along its contact with the frontal the parietal
is concave anteriorly, whereas in higher ruminants it is
usually convex. The dorsal aspect of the parietal is
divided quite distinctly into a flat anterior and a crested
posterior part. The anterior part is continuous with the
frontal and forms the posterior triangular portion of the
skull table. In the posterior part, the parietal crests
connect the postorbital bars to the sagittal crest. The
sagittal crest and the adjacent parts of the parietals slope
downward toward the nuchal eminence. The parietals
meet the supraoccipital bones 8 to 10 mm short of the
nuchal eminence.
The parietals form much of the lateral wall of the
braincase (Fig. 1D-E). They include both the narrowest
part, across the postorbital constriction, and the widest
part, above the glenoid fossa. The difference in width
between these two parts is, as in Moschus, far more
dramatic than in higher ruminants. The anterior edge of
each parietal follows a vertical suture from the postorbital
bar ventrally behind the orbit meeting the frontal for
about 5 mm. It extensively contacts the orbitosphenoid.
The anteroventral comer of the parietal meets the
alisphenoid along a sinuous suture less than 5 mm long,
just above the level of the zygomatic arch. The long
ventral margin of the parietal rises gently as it passes


posteriorly toward the nuchal eminence. Finally, the
parietal meets the supraoccipital along a vertical contact
about 12 mm long.

SQUAMOSAL
The upper edge of the squamosal overlaps the
parietal and supraoccipital along the side of the
braincase. The suture passes anterodorsally from the
middle of the mastoid crest (about 13 mm below the
nuchal eminence in UF 19257, about 14 mm in F:AM
33720) and follows the edge of the supraoccipital for 7
or 8 mm. There it meets the parietal forming a long
descending contact below the widest part of the cerebral
expansion. A narrow tongue of the squamosal turns
ventromedially to enter the posteroventral corner of the
orbit where it is tightly fused with the alisphenoid. At
this point the squamosal is very thick and assists the
alisphenoid in supporting a strong tubercle for the lateral
pterygoid muscle. The tubercle is strong as in Moschus
but does not reach the extremely well-developed
condition seen in Tragulidae and Protoceratidae (Patton
& Taylor 1973:376). The squamosal suture then turns
posteriorly along the lateral edge of the alisphenoid,
nearly touching the foramen ovale, and passes to the
bulla and mastoid region.
The zygomatic-glenoid portion of the squamosal
extends laterally 8 to 10 mm beyond the widest part of
the braincase. It is supported by anterior and posterior
crests. The posterior zygomatic crest is an anterior
continuation of the mastoid crest as it turns anteriorly
and widens above the ear region. It becomes still wider
and thicker above the glenoid fossa. The splint-like
zygomatic process of the squamosal overlaps that of
the jugal. The zygomatic process thus spans a 12 mm
gap between the glenoid fossa and the postorbital bar,
where the squamosal terminates.
The glenoid fossa is nearly rectangular in outline
(Fig. IB), being about 15 mm wide and 6 mm long. In
this respect the Pseudoceratinae differ from most other
ruminants. The longitudinal channel for the capsular
ligament on the medial side of the glenoid fossa is
present, as in virtually all ruminants, but it is not as strongly
developed as inMoschus. The glenoid fossa is bounded
posteriorly by a very broad, very strong postglenoid
process. It is about 10 mm wide and nearly 5 mm deep
in both Pseudoceras and Floridameryx. The relative
size of the process is greater than in any other ruminants,
although it most closely resembles that inMazama and
other Cervidae. The postglenoid foramen is small,
relatively smaller even than in Tragulidae, and in striking
contrast to the large foramina in Moschus and higher







ruminants. The lateral side of the postglenoid process
turns anteriorly and joins a strong zygomatic crest, thus
enclosing the lateral side ofthe glenoid fossa. This lateral
glenoid crest is only weakly developed inMoschus and
some higher ruminants. This strong lateral crest, the
broad and deep postglenoid process, and the concave
glenoid surface evidently provided the Pseudoceratinae
with an extraordinarily secure jaw articulation,
presumably a feature related to powerful occlusion of
the enlarged canines in presumed males.
A supraglenoid foramen opens above the zygomatic
crest posterior to the glenoid region. In the skull of
Pseudoceras skinneri it is over 3 mm in diameter and
in Floridameryxfloridanus it is only slightly less. This
foramen is minute or absent in Tragulidae and in most
higher ruminants, but a moderate-sized supraglenoid
foramen occurs as a variable feature in Moschus and
Cephalophus. This foramen evidently provides an
alternative to the postglenoid foramen as a route for
venous drainage from the lateral cerebral region. In
Moschus and higher ruminants, a large excavation
above the external auditory meatus, the suprameatal
fissure, provides still another alternative route, but this
excavation is not developed in Pseudoceratinae nor in
Tragulidae.
Above the external auditory meatus and behind
the zygomatic arch is the post-tympanic neck of the
squamosal. In most primitive artiodactyls this region is
prominent, whereas in most ruminants it is weakly
developed in comparison with the mastoid process
immediately posterior to it. It is likewise very weak in
Pseudoceratinae. Instead, a long tubular meatus
dominates this area.

AUDITORY BULLA
The bulla has a spheroidal outline in
Pseudoceratinae. It lacks the anteromedial-
posterolateral elongation observed inMoschus and most
higher ruminants. It is hollow and moderately inflated;
the degree of inflation lies between the extremely swollen
condition in Cephalophus or the Tragulidae and the
flattened condition of Moschus and most Cervidae. In
size and degree of inflation it resembles the bulla of
Hydropotes, although it is constructed quite differently.
The medial wall of the bulla touches the basioccipital
broadly in Pseudoceras, whereas in Floridameryx a
small fissure bounds the bulla medially. The long tubular
meatus rises posterodorsolaterally so that its lip touches
the posterior edge of the zygomatic crest. It is longer
and more nearly vertical than in Moschus or any higher
ruminants, and it is unique in attaining the level of the


BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(2)

zygomatic crest. Its aperture faces dorsally and
posteriorly rather than laterally and posteriorly as in most
ruminants. The tympanohyal process lodges at the base
of the tubular meatus where it fuses with the lateral
wall of the bulla. In most other ruminants the
tympanohyal process lies farther posteriad, close to or
in contact with the paroccipital process. In Moschus,
Hydropotes, and Cephalophus, however, the
tympanohyal is set anterolaterally near the base of the
meatus, as in Pseudoceratinae. The styliform process
is weakly developed and blunt, in contrast with that of
Moschus and most Cervidae.

PERIOTIC
The following description is based on a petrosal
removed from UF 19257 (Fig. 2). After study and
illustration (Fig. 2), it was reattached to the skull. This
dense disc-shaped bone is covered ventrally and laterally
by the bulla and is inseparably fused with the mastoid
along its lateral margin. Its medial margin lies just dorsal
and lateral to the basioccipital. The medial margin does
not contact the basioccipital and lacks the strong process
and notch which in Tragulus contact the basioccipital
and form part of the median lacerate foramen.
Posteromedially, behind the posterior lacerate foramen,
the periotic is braced against the basioccipital, about as
inMoschus. The periotic is somewhat longerthan wide,
its long axis diverging posterolaterally from the long axis
of the skull at an angle of about 45 degrees. The ventral
surface of the periotic faces anteroventolaterally in the
usual manner.
The structural details of the periotic are complex
partly because of the intricate structures of the middle
and inner ear, and partly because of the diverse cranial
nerves and vessels that commute through this part of
the braincase. The ventral face of the periotic lies in a
plane essentially parallel to that of the endocranial face
and is separated from it by a thickness of about 4 mm.
The ventral (basicranial) aspect will be described first
(Fig. 2A).
The globose promontorium dominates the ventral
aspect of the periotic. The contours of its surface closely
follow the first two cochlear whorls, the posterior being
the larger. Athird complete whorl is present anteriorly,
but is too small to be reflected by the promontorial
contours. The gentle swale between the first two
cochlear whorls reveals no trace of any vessels or nerves
in any of the specimens at hand. As in ruminants
generally, no branch of the internal carotid artery crossed
the promontorium.





Webb, S.D.: Revision of the Extinct Pseudoceratinae

A
Rn F. Pror

Roundj Fen. M
MEp
M. Stape,:I 0I -_ _


4 Int. Aud. Meatus
I-__ Cochl. Orifice


1cm


Figure 2. Left Periotic of Floridameryxfloridanus, UF 19257, from the Withlacoochee River 4A Site in A, basic-
ranial, and B, endocranial, views. Promont.(Promontorium), Round Fen.(Round Fenestra), M.Staped. (Stapedial
Muscle Fossa), M.Tens. Tymp. (chamber for Tensor Tympani Muscle), Epid Rec. (Epitympanic Recess), Oval Fen.
(Oval Fenestra), Fac. Canal (Facial Canal Opening), For. Petrosal Nerve (Foramen Petrosal Nerve), Fallop. Hiatus


(Fallopian Hiatus), Floc. Fossa ( Flocular Fossa), Int.
(Cochlear Orifice).

The rounded medial edge of the periotic is thin and
forms a relatively narrow band beside the promontorium.
In Moschus, by contrast, the band is much wider and
thicker. The closest comparison in this feature is with
Tragulidae where, although not smoothly rounded, the
medial edge of the periotic is narrow and thin.
Presumably, this feature is related to the development
of a substantially inflated bulla, which protects the medial
edge of the periotic by covering it ventrally.
The round fenestra (fenestra cochleae) faces
directly posteriad as in Moschus and Cervidae. In
Tragulidae, on the other hand, it faces posterolaterally.
The ventral lip of the fenestra nearly conceals the
aperture in Pseudoceratinae, whereas in most ruminants
it is well exposed. Facing the fenestra posteriorly is a
high bony wall, formed from the mastoid, resembling
that in most higher ruminants, but missing in Tragulidae.
Likewise, a bony curtain separates the entrance to the
round fenestra laterally from the fossa for the stapedial
muscle. In this feature, also, the Pseudoceratinae
resemble most higher ruminants and differ from
Tragulidae.
The deep fossa for the stapedial muscle lies
posterolateral to the round fenestra. It is not as elongate
transversely as inMoschus and the Cervidae but is more
deeply pocketed. In particular, the lateral edge of the
stapedial fossa is marked by a steep wall well above the
level of the facial canal, a feature not observed in
Cervidae or Moschus, but more nearly approached in
other Gelocidae and in Tragulidae.
The oval fenestra (fenestra vestibulae) lies
anterolateral to the round fenestra. A distinct bony crest
extends along the edge of the promontorium from the


Aud. Meatus (Internal Auditory Meatus), Cochl. Orifice


round to the oval fenestra, evidently serving as an
attachment for part of the stapedial muscle. I have not
observed such a strong crest in other ruminants, although
a weakly developed crest commonly occurs inMoschus.
The long axis of the fenestra ovale parallels the
cochlear axis. In Pseudoceratinae, as in Tragulidae,
the aperture is nearly circular, in contrast with Moschus
and the Cervidae in which the length is fully twice the
width. The fenestra ovale is pressed closely against
the wall of the promontorium. The bevelled edge for
the stapes footplate thins considerably along the medial
side as in Tragulidae, whereas inMoschus and Cervidae
the bevelled edge is continuously broad. Corresponding
features of the stapes itself are described below.
The facial canal emerges through the ventral
surface of the periotic immediately posterolateral to the
fenestra ovale. In Tragulidae the facial canal emerges
farther forward, anterolateral to the fenestra ovale, but
in this feature the Pseudoceratinae resemble higher
ruminants. In Floridameryx, the opening of the facial
canal lies well below the level of the oval fenestra and
is separated from it by a crest. The difference in
elevation is much less in Tragulidae, Cervidae, and
Moschus, and in them no crest sets off the facial canal.
The facial canal may be followed anterodorsally as it
passes above the lateral side of the fossa for the tensor
tympani muscle. In the Pseudoceratinae, the small
epitympanic recess lies well forward of the facial canal
opening. It lies lateral to the tensor tympani fossa and
is essentially continuous with it. This same arrangement
is found in other Gelocidae, inMoschus, and in higher
ruminants. In the Tragulidae, on the other hand, the
epitympanic recess lies lateral or posterolateral to the







facial canal, entirely separated from the tensor tympanic
fossa. In Pseudoceratinae and other Gelocidae, an
unusually prominent crest separates the opening of the
facial canal from the tensor tympani fossa. In
Tragulidae, by contrast, the facial canal emerges within
the fossa, and no line of demarcation can be detected.
In Moschus and higher ruminants the condition is
intermediate, in that the canal opens posterior to the
edge of the fossa but the boundary is marked only by a
subtle decrease of slope or at most a faint crest.
In Pseudoceratinae, the tensor tympani muscle is
housed in a large spheroidal chamber anterior to the
fenestra ovale and the ventral opening of the facial canal.
The medial side of the chamber is represented by the
flattened bone surface covering the distal cochlear
whorls. The anteroposterior length of the chamber is
no greater than its transverse width, as in other
Gelocidae, but in marked contrast with Moschus and
most Cervidae in which the chamber is longer than wide
and extends as far anteriorly as the terminal cochlear
whorl. This hemispherical tensor tympani chamber is
relatively and absolutely much larger and more deeply
pocketed into the roof of the middle ear in
Pseudoceratinae and other Gelocidae than in Tragulidae;
resembling in that regard Moschus and most higher
ruminants.
A general explanation of several special features
of the gelocid periotic is lateral compression ofthe middle
ear by the mastoid wall. This forces the epitympanic
recess anterior to the facial canal and makes it join the
muscular fossa. The facial foramen is shifted
posteromedially so that it opens immediately below the
fenestra ovale. It also causes the facial canal to curve
around toward the round fenestra. And finally, the
muscular chamber is tucked more deeply under the
anterolateral wall of the periotic.
The endocranial side of the periotic (Fig. 2B)
consists of a thinner ventromedial portion including the
internal auditory meatus, and a thicker dorsolateral
portion housing the semicircular canals. The internal
auditory meatus is in fact a common orifice for several
canals passing from the brain through the periotic. It is
divided by a low bony ridge into a smaller lateral fossa
and a larger medial fossa. This dividing ridge is low as
in Gelocus, Moschus, and most Cervidae, not prominent
as in Tragulidae. The lateral fossa within the internal
auditory meatus contains two openings. A small posterior
opening enters the vestibular canal, through which the
superior ramus of the vestibular nerve reaches the outer
ampulla of the utriculus. The large anterior opening
provides passage for the facial nerve via the Fallopian


BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(2)

Hiatus as it passes ventrally along the lateral side of the
cochlea and then turns posteriad into the tympanic cavity
as described above.
The medial fossa within the internal auditory
meatus contains one large and two small openings. The
large opening, the internal acoustic pore, conducts the
acoustic nerve anteroventrally to the organ of Corti within
the cochlea. The two smaller openings pass laterally
through the wall of the periotic into the middle region of
the cochlea. These features in Pseudoceratinae closely
resemble those in most ruminants.
A rather large cochlear orifice opens into the medial
edge of the periotic about 2.5 mm medial to the internal
auditory meatus. It opens ventrally inside the cochlea
near the round fenestra as in other ruminants. In the
specimen of Floridameryx, these two orifices are about
half a millimeter apart. On the lateral edge of the
periotic, a slit-like opening passes posteriorly into the
periotic bone. This Fallopian hiatus represents the entry
of the superficial petrous nerve into the Fallopian
aqueduct about midway between its endocranial and
tympanic openings. It closely resembles the hiatus in
other Gelocidae, Moschus, and most higher ruminants,
but differs from the Fallopian hiatus in Tragulidae, for in
that family the hiatus lies more nearly on the tympanic
face than on the edge of the endocranial face, and it
has a more anterior position than in Gelocidae or higher
ruminants.
The dorsolateral portion of the periotic has an
irregular surface reflecting the adjacent surface of the
cerebellum and, laterally inside the periotic, the
semicircular canals. Raised ridges forming aY-pattern
represent the superior semicircular canal passing
dorsolaterally, the posterior semicircular canal fading
away posteriorly, and the common root of these two
canals. Of three lateral cerebeller lobes represented
by fossae, only the floccular fossa is very distinct. It
lies largely within the arc of (and ventral to) the superior
semicircular canal. It is almost hemispherical with a
diameter of about 3.5 mm and a depth of about 2.5 mm.
The resemblance of this floccular fossa to that of
Moschus is very close. As Sigogneau (1968) has
observed, a deep floccular fossa is found in Moschus
and Hydropotes, but not in other modern Cervidae. An
even deeper floccular fossa occurs in other Gelocidae.
Since a very deep floccular (or subarcuate) fossa also
occurs in Hypertragulidae and Camelidae, as well as
Cainotheriidae and Xiphodontidae, it is evidently a
primitive feature shared by many early selenodont
artiodactyls.





Webb, S.D.: Revision of the Extinct Pseudoceratinae


In Tragulidae, however, the morphology on the
endocranial side of the semicircular canal is markedly
different. The only deep fossathat might be homologous
to the floccular fossa lies posterodorsal (not ventral) to
the superior semicircular canal. Other features in this
region also differ radically in Tragulidae, as compared
with Gelocidae and Moschidae. For example, a large
canal, presumably for the superior petrosal vein, passes
through the upper portion of the periotic lateral to the
semicircular canals; in Pseudoceratinae, as in most
ruminants, no such canal exists.

MASTOID
The mastoid is difficult to describe, partly because
it is largely overlapped by the squamosal anteriorly and
dorsally and by the occipital posteriorly and ventrally,
and partly because the suture lines bounding it fuse early
and often become obscure. Fortunately, however, one
specimen ofFloridameryx, UF 13834, is a juvenile with
parts of the squamosal missing, so that both mastoids
are well delineated. The lateral face of the mastoid is
broadly expanded (over 9 mm wide) under the cover of
the squamosal and rises to nearly the same height along
the mastoid crest of the squamosal. Only the thickened
posterior edge of this face (about 2 mm wide) is exposed
posterior to the squamosal, and anterior to the
exoccipital. This posterior exposure most closely
resembles that inMoschus and most higher ruminants;
it is much narrower and strongly crested compared with
the mastoid in Tragulidae.
This narrow exposure makes up the ventral half
ofthe mastoid crest ofthe squamosal. From thejunction
of the squamosal and supraoccipital it extends
anteroventrally to the bifurcation of the mastoid and
zygomatic crests, just behind the external auditory
meatus. There it gives off a smaller crest that proceeds
ventrally down to the tip of the small mastoid process.
At this point the mastoid exposure is extremely narrow,
being sandwiched between the post-tympanic neck of
the squamosal and the base of the paroccipital process.
The emergence of the stylomastoid canal marks the
squamosal-mastoid junction about 6 mm below the
external auditory meatus and nearly the same distance
anterior to the tip of the mastoid process. The narrow
posterior edge of the mastoid is overlapped by the
exoccipital to which it is fused. The mastoid foramen
may open at the upper end of the mastoid-paroccipital
suture, but in Pseudoceratinae it is minute or absent.
The lower edge of the lateral wall of the mastoid is
solidly fused with the periotic bone even in young
specimens.


OCCIPITAL
The dorsal portion of the occipital is notable for its
prominent external occipital protuberance. The
protuberance is heavy and diamond-shaped, most closely
resembling that in Tragulus and smaller than that in
Moschus. The anterior point connects with the sagittal
crest of which the occipital part is between 9 and 10
mm long. The dorsal surface of each occipital forms a
trapezoidal surface. The anterior side descends nearly
vertical for about 12 mm bordering the parietal. At the
squamosal the occipital border turns posteroventrally to
the mastoid bone and forms the high mastoid crest along
a straight suture of nearly 7 mm length. In the
development of the occipital protuberance and sagittal
and mastoid crests, the Pseudoceratinae resemble
Gelocus and Moschus, whereas in higher ruminants
these features are largely subdued.
The posterior aspect of the occipital forms an
almost perfect equilateral triangle. It has a more pointed
apex than in Moschus; and the region is much wider
than tall and the upper apex is very broadly rounded, as
in higher ruminants.
A strong median occipital crest extends ventrally
from the posterior point of the diamond-shaped external
occipital protuberance about as in Moschus. At the
lower end on either side of the midline atubercle for the
atlanto-occipital muscle is weakly defined. The major
nuchal muscle attachment areas occupy most of the
posterior aspect of the cranium. The upper pair are for
the nuchal ligament and complexes muscles. The lateral
third of the occipital region is set off by a vertical crest
for the splenius and obliquus muscles.

EXOCCIPITAL
The condyle and the paroccipital process are the
principal features of the exoccipital. The condyles agree
in their disposition and shape with those of most
ruminants. The ventral condylar surface terminates
anteriorly in a transverse ridge as in homed ruminants.
It is somewhat stronger in Floridameryx than in
Pseudoceras. Such a ventral condylar ridge does not
occur in Tragulidae but is found in Moschus and
Dremotherium. Meade (1906) interpreted these as stop
mechanisms for homed ruminants, but their occurrence
in Merycoidodontidae, Moschidae, Camelidae, and
Protoceratidae suggests that they originated earlier in
artiodactyls with enlarged canine teeth (Webb 1965).
The paroccipital process in both Pseudoceras and
Floridameryx is unusually large and posteriorly
reflected. It slopes so strongly posteroventrally that the
tip lies almost directly lateral to the point of the occipital




BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(2)


A

B




5 cm-

C



D


E



F

5 cm
Figure 3. Occlusal views of upper and lower teeth of Floridameryxfloridanus from the Withlacoochee River 4A
Site, Florida. A. UF 13833, left maxilla with P2-M3. B. UF 13836, right maxilla with Cl, P2-M3. C. UF 13832
holotypee), left cl, p2-m3. D. UF 19395 (allotype), left p2-m3. E. UF 225879, left p2-m3. F. UF 225882, right
(reversed) p2-m3. Lateral views of mandibles shown in Figure 4. Upper scale bar is for the maxillae, lower scale
bar is for the mandibles.





Webb, S.D.: Revision of the Extinct Pseudoceratinae


condyles. The blade-like process is expanded
anteroposteriorly. It tapers from a maximum width of
over 9 mm to a blunt tip. Its length, from its base near
the mastoid process to its tip is about 14 mm. It curves
slightly media near the tip. Because of its strongly
posterior orientation, the tip of the paroccipital process
does not extend below the level of the basioccipital, as
in Moschus and most other ruminants.
The condyloid fossa is narrow and deeply pocketed
between these structures. It contains two relatively large
foramina, the condyloid foramen and the hypoglossal
foramen. The former is smaller and provides the ventral
exit of the occipital canal from the braincase. The latter
is larger, lies farther anteroventral, and transmits the
hypoglossal nerve and the posterior meningeal branch
of the occipital artery.

BASIOCCIPITAL
A pair of shallow concavities, each with a broad
trapezoidal outline, marks the basioccipital region. They
provide the origin for the various cervical flexor muscles
which are considerably enlarged. Their arrangement in
broad concavities closely resembles the condition in
Moschus, and differs considerably from that in
Tragulidae with their narrow basicranii. In the skull of
Pseudoceras skinneri the bulla is broadly appressed
against the lateral edge of the basioccipital, while in
specimens ofFloridameryxfloridanus it is continuously
separated by a gap of no less than a millimeter, about as
inMoschus. The anterolateral edge of the basioccipital
is emarginate, forming the medial wall of the jugular
canal and immediately anterior to it the median lacerate
foramen for the carotid artery and nerve.

BASISPHENOID
The anterior edge of the basioccipital is solidly
fused with the basisphenoid in the three available
specimens. The line of fusion is marked by a pair of
basilar tubercules, moderately developed about as in
Moschus and Dremotherium. As Sigogneau (1968)
has observed, these tubercles are absent in higher
ruminants, but are well developed in Tragulidae. They
are separated by a groove that passes along the midline.
The ventral surface of the basisphenoid is convex, and
it narrows as it passes anteriorly between the pterygoid
processes.

UPPER DENTITION
The dental formula is 10, C1, P2-P4, M1-M3 (Figs.
1B, 3A-B). The complete absence of upper incisors is


confirmed in Floridameryx by premaxillae that lack
alveoli, including UF 13833 and 13836.
The upper canines appear to be of two sizes,
dimorphism that is more fully documented in the lower
dentition. Only the larger, presumably male, upper
canines are adequately represented. The
anteroposterior diameter of the root just above the crown
ranges from 5.1 to 5.5 mm in four specimens of
Floridameryx floridanus. The transverse diameter
ranges from 3.2 to 3.7 mm in the same sample. The
upper canine alveolus in UF 19270, however, is only 2.7
mm in anteroposterior diameter by 2.4 mm in transverse
diameter. Presumably this specimen represents a
female.
A remarkable feature of the male upper canine is
heavy occlusal wear on the anterior face, as in
Tayassuidae. The wear plane is nearly vertical and
transverse, but with slight lingual and ventral beveling
(Fig. 3B). One nearly unworn upper canine (UF 19272)
exhibits a strong anterior crest with a small wear facet
beginning near the tip. Others have nearly half the crown
worn away from tip to base.
The root of a mature upper canine (UF 19271) is
completely closed and had ceased to grow. The root is
16.2 mm long, while the heavily worn crown is 5.7 mm
long. The canine makes a gentle spiral along its length.
The root arcs forward and downward, assuming an
essentially vertical position where the crown emerges
from the maxillary. The tip of the canine is twisted
outward around its own axis, so that the tip lies about 6
mm lateral to the root and to the cheek teeth. Evidently
when the canine first erupts the tip receives the initial
wear, but as it continues to emerge the tip twists
downward and posterolabially so that the wear facet
gradually shifts dorsolingually onto the anterior crown
face.
P2 and P3 are long, bladelike teeth with a high
secant labial wall (Fig. 3A-B). The parastyle is small
but distinct and produces a persistent labial rib. The
high principal cusp is the paracone. On the labial wall it
forms a very prominent rib, set off by deep grooves
before and behind. The paracone is broadly connected
to an oblique bladelike metacone, which accounts for
more than half of the tooth length. The paracone-
metacone blade greatly resembles that of a carnivore
carnassial, and it surely had a shearing function. The
deep postparaconal groove functioned in much the same
manner as the carnassial groove, that is to facilitate
clearing the "blade." The long labial shearing facet
slopes about 60 degrees above the horizontal in newly







erupted teeth, but declines to less than 30 degrees in
well-worn teeth.
The lingual structures of P2 and P3 are relatively
weak. They consist of a minute midlingual protocone
supported by a small lingual root. The entire lingual
margin is reinforced by a continuous cingulum which is
especially strong at the anterolingual and posterolingual
ends. As the premolars wear down, the protocone soon
disappears as a distinct cusp, and forms a cross link
between the labial blade and the lingual cingulum (Fig.
3A). At the same time anterolingual and posterolingual
fossettes appear. In advanced wear, the posterolingual
fossette is completely destroyed.
P4 consists of two crescentic cusps forming, in
effect, a half molar, as in most artiodactyls (Fig. 3A-B).
This tooth is three-rooted, as are P2 and P3, but here
the protoconal root is very well developed. The
posterolabial root is the weakest. The labial wall has a
strong parastyle, an even stronger paracone, and,
separated by a considerable gap, an elongate metacone.
These labial structures partly resemble their counterparts
in P2 and P3, but the camassial function is much weaker.
The fossette is large and persistent, but unlike higher
ruminants, it occupies an anterior rather than a central
position. One or a few minute ephemeral posterior
fossettes sometimes are present in early wear stages.
P4 has a higher crown than the preceding premolars.
The upper molars closely resemble one another
and may be described together. Each successive molar,
however, increases in height and length over the
preceding (Fig. 3A-B). In Floridameryx floridanus
the crown height of a slightly worn Ml (UF 19263)
measured along the mesostyle, is about 4.3, while M2
measures 6.8, and a faintly worn M3 reaches a height
of 8.1. An unworn M3 (UF 19262) measures 8.5 mm
high. The upper molars are transversely compressed, a
feature that is more obvious in the longer proportioned
posterior molars.
The paracone and metacone are narrow
subcircular cusps, as is clearly indicated by their pinched
appearance within the fossettes. Nonetheless they
produce a high bicrescentic ectoloph. Labially these
cusps produce a prominent parastyle, paraconal rib, and
mesostyle, only a weak metaconal rib, and a moderate
metastyle. The M3 metastyle is stronger and grooved
posterolabially. The paraconal rib is not reflected
forward, nor does it join the parastyle as in Tragulidae.
The lingual cusps are crescentic or somewhat
angular, with their vertices directed anterolingually. The
adjacent midlingual limbs do not join each other directly
and firmly, as one might expect in such hypsodont taxa.


BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(2)

Instead, the posterior limb of the protocone and the
anterior limb of the metaconule often proceed separately
toward the mesostyle, thinning as they do so. The
midlingual valley, therefore, tends to be quite deep, often
extending labially to the center of the fossettes in early
wear stages. The nature of this midlingual commissure
is weak but extremely variable. For example, in each
molar of UF 19264 the posterior limb of the protocone
is short, posteriorly directed, and does not reach the
metaconule until a very late wear stage. The molar
protocones of this specimen thus resemble those in
Gelocus and Tragulus. In UF 19265, while the adjacent
limbs are about as poorly united, it is the anterior limb of
the metaconule that is short, anteriorly directed, and fails
to join the protocone until a very late wear stage. In
either event, the midlingual commissure is weak and
variable in Pseudoceratinae.
The fossettes are simple crescents with no folds
or processes. They persist for most of the crown height,
only disappearing during about the last 2 mm of wear.
A short endostyle is usually present. It decreases in
size from the M 1 to the M3 and is often absent or obscure
on M3. The endostyle arises at the anterolingual base
of the metaconule and may or may not touch the base
of the protocone. No cingulum is present on
pseudoceratine upper molars. Thin cementum usually
covers upper and lower cheek teeth; it is especially
evident in the fossettes.
The deciduous upper premolars are preserved in
two maxillaries, UF 19262 and 19264. The only evidence
of DP2 unfortunately is the posterior alveolus which
indicates that it was a narrow tooth. The anterior portion
of DP3 is narrow, consisting only of two closely
appressed labial cusps. They are not elongate nor well-
separated as in tragulids. It is impossible to identify an
anterolingual cingulum due to the advanced wear stage
of this tooth; if it had such a cingulum it was weak. The
posterior portion of DP3 is molariform with a weak but
distinct protocone. This tooth is 6.2 long and 4.7 wide
in both specimens. The broad molariform pattern of the
posterior portion of DP3 closely resembles that in
Gelocus, Bachitherium and Prodremotherium and
foreshadows the more fully molariform condition of
deciduous premolars in higher Pecora.
DP4 is fully molariform and about equals the first
upper molar in length and width. It differs from true
molars only in its much lower crown, thinner enamel
and weaker mid-lingual cusp. In UF 19262 DP4
measures 6.2 long and 5.9 wide; in UF 19264 these
dimensions are 6.3 by 6.0. DP4 in Pseudoceratinae
presents essentially the same morphology as in





Webb, S.D.: Revision of the Extinct Pseudoceratinae


Bachitherium and Prodremotherium (Geraads et al.
1987).

LOWER DENTITION
The dental formula is i 1-i3, c 1, p2-p4, m 1-m3. The
first lower incisor has an expanded spatulate crown,
with a horizontal wear surface 5 mm wide and 5 mm
deep in UF 19395 (Fig. 4B). The lateral edge of the
incisor flares widely, whereas the medial edge is nearly
straight. This moderately worn incisor has an anterior
face of thickened enamel about 8 mm long, inclined at
an angle of about 30 degrees above the horizontal. The
root is about 9 mm long and tapers rapidly to a diameter
of about 2 mm.
The i2 and i3 are much smaller than the first. One
well-preserved dentary, UF 225886, reveals a heavily
worn i2 in the same horizontal plane as the il. It is 2.7
mm wide, and the anterior enamel face is still 5.1 mm
long. The root is only 1.7 mm wide and 2.5 mm in
dorsoventral diameter. The i3 is not preserved in the
Floridameryx sample, but the alveoli suggest that it is a
smaller replica of the i2.
The permanent incisors of Floridameryx
floridanus erupted quite late in life. The tip of an
unerupted i2 lies deep in the crypt of UF 13832, in which
the m3 had already fully erupted. The i 1 is unerupted in
two mandibles (UF 225895 and 225896) with m2 lightly
worn. Evidently the i 1 began to erupt at about the same
time the m3, and the i2-i3 did not emerge until the m3
had become well worn.
The most remarkable dental feature of the
Pseudoceratinae is the presence in males of a strong
upright lower canine that occludes against the anterior
face of the upper canine (Figs. 3C, 4B). In all other
known pecorans, by contrast, the lower canine is
incisiform. Although quite evident in the type of
Pseudoceras skinneri, this upright lower canine does
not occur in all pseudoceratines. For example, a right
mandible of Pseudoceras (F:AM 53365) from Clayton
Quarry in Nebraska has an incisiform canine. The
allotype of F. floridanus also illustrates the presumed
female morphotype (Fig. 4).
The nature of lower canine dimorphism is
elucidated by the large sample of Floridameryx
floridanus mandibles from Withlacoochee River 4A.
As shown in Figure 5, about half of the mandibles support
large upright lower canines with vertical wear facets on
their posterior surfaces. Presumably these mandibles
represent male individuals. Other mandibles have
slender procumbent lower canines and presumable
represent females. Both types are about equally


represented at all ages, using the wear stage of ml as
an indication of age. A subtle tendency for higher
mortality in probable males than females may be noted
in this figure. This pattern is familiar in ruminant species
in which young males become social outcasts and thus
experience heavier selection than young females who
generally enjoy the security of the herd. The caniniform
lower canine does not change ontogenetically but
evidently is a sex-linked (male) character. The presumed
female lower canines are incisiform as in other
ruminants.
The male lower canine is recurved and attains a
total length of over 15 mm. The crown is about 7 mm
high in both Pseudoceras and Floridameryx and leans
outward from the plane of the mandible at an angle of
about 20 degrees. It bears a crest that passes from the
tip down the anterior face and curves anteromedially
near the base. The medial side is nearly flat, with two
faint concavities running vertically. In old individuals
heavy wear extends vertically from the tip down the
posterior face of the canine. In very old specimens,
such as UF 225886, the wear extends down onto the
root and produces a notch more than 1 mm deep in the
posterior profile of the canine. Wear striations extend
obliquely from dorsolingual to ventrolabial across the
posterior face of the canine. On the lingual side, nearly
horizontal grooves cut into the enamel just above the
presumed gum line. In old individuals, such as UF
225911, the groove cuts completely through the lingual
enamel of the canine from the anterior face to the
posterior wear face. Presumably these grooves resulted
from abrasion by vegetation and adhering sediments as
they were pulled into the mouth by the tongue. Scott
(1940:381) noted similar abrasion in Archaeotherium
canines and attributed them to pulling sand-laden roots.
The postcanine diastema, ranging from about 15
to 20 mm (Fig. 4; Table 1), is relatively short compared
with the diastemata in Moschus, Cervidae, or other
higher ruminants. It is about the same relative length as
in the Tragulidae.
The lower premolar series is noticeably reduced
in length relative to the molar series in Pseudoceratinae
(Figs. 3-4; Table 1). This premolar abbreviation reaches
its extreme in Floridameryx floridanus, but even in
Pseudoceras skinneri the premolars are short as
compared with those in other primitive ruminants. Loss
of the p has contributed to this abbreviation. A dp i
does exist; in one juvenile dentary it appears as a small
leaf-shaped tooth immediately anterior to a nearly
identical dp2. Within the premolar series, size increases
from anterior to posterior as in Moschus and higher





BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(2)


5 cm


Figure 4. Mandibles of Floridameryxfloridanus from the Withlacoochee River 4A Site, Florida in lateral view.
Occlusal views of these specimens are Figure 3C-F. A. UF 13832 holotypee). B. UF 19395 (allotype). C. UF
225879. D. UF 225882 (reversed).


-1


) F'13 8
hw'-%0 _3Z





Webb, S.D.: Revision of the Extinct Pseudoceratinae


Table 1. Measurements of dentitions of Floridameryxfloridanus from Withlacoochee River 4A, Florida. Abbre-
viations for measurements: DIA, length of postcanine diastema; LM, length of molar row; LP, length of premolar
row. Detailed measurements of individual cheekteeth in Pseudoceras and Floridameryx are beyond the scope of
this paper, but are available upon written request from the Department of Vertebrate Paleontology at the Florida
Museum of Natural History.


Maxilla
Light wear


Mandible
Light wear


Medium Wear
LP
17.5
1

Heavy Wear
LP
17
3


LM
24
5


LM
26
2


LM
23
3


ruminants generally, but in marked contrast with
conditions in Tragulidae and more primitive selenodonts.
The premolars are constructed on a tragulid- or
camelid-like pattern, altogether different from that of
Moschus, Cervidae, or other higher ruminants. Each
premolar is narrow, wedge-shaped, lacks multiple lingual
folds, and has a distinct peak in its profile (Fig. 4). The
enamel on the premolars and molars is faintly crenulated.
The p2 is a narrow tooth with three relatively simple
cuspids in an anteroposterior row. The paraconid is low
and slightly inflected to the lingual side. The central
cuspid (metaconid) is the tallest one. From its lingual
wall projects a rib which is probably homologous with
the posterolingual crest on more posterior premolars.
The talonid is low and broad. On its lingual side, a minute
entoconid and a posterior transverse crest enclose a
minute fossettid.
The p3 is an enlarged and especially broadened
version of p2 (Fig. 3C-E). The paraconid is extended
anterolinguallyto form aparalophid crest. The metaconid
rises centrally above the other cusps and extends from
its posterior slopes a strong posterolabial and a weak
lingual crest. The broad talonid is enclosed labially by
the metaconid crest. A small entoconid occupies the
center of the basin. A small talonid valley opens
posterolingually between the entoconid and the posterior


Medium Wear
LM
27
6

Heavy Wear
LM
27


DIA
16
6


DIA
15.5
6


DIA
18
1


transverse crest. After moderate wear stages, however,
it becomes a posterolingual fossettid.
The p4 differs from p3 in its larger size and in
some structural details (Fig. 3C-E). The paralophid is
stronger and encloses a very small trigonid basin bounded
lingually by a minute cingulum. The metaconid sends
off a strong posterolingual crest which passes posteriad
and with the entoconid forms a complete posterolingual
wall. The talonid valley is enclosed in very early wear
stages to form a long narrow fossettid which trends
posterolingually.
The lower molars are moderately high-crowned
and strongly compressed transversely. They are only a
little higher-crowned than lower molars of some other
progressive Gelocidae such as Prodremotherium. But
the strong compression of pseudoceratine molars gives
the impression of much greater height. Moreover,
because hypsodonty is a ratio of crown height to occlusal
area, the Pseudoceratinae are surely among the most
hypsodont of hornless ruminants, rivaled only by the
hypertragulid Hypisodus.
The molars increase in size and height from the
ml to m3 (Figs. 3-4). Nonetheless, they may be
described together, as there are few other differences
between them. The metaconid and entoconid are
elongate and rather strongly flattened. They thus
contrast strongly with the bulbous lingual cuspids of





BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(2)


* 0


00*


C1 Anteroposterior Diameter

Figure 5. Variation by age and sex in the Withlacoochee River 4A sample of Floridameryxfloridanus, based on 22
mature dentaries; sex determined by dimorphic canine size, age by wear heights of ml. The holotype specimen is
indicated by the star.


Gelocus. The flatness of the wall is broken by two
features: (1) a small but sharp parastylid that persists
even into moderately advanced stages of wear; and (2)
a persistent groove separates the metaconid from the
entoconid. No metastylid is present. Neither the
metaconid nor the entoconid shows any trace of the
folding so characteristic of Dorcatherium or other
Tragulidae.
Perhaps the most remarkable feature of
pseudoceratine lower molars is the lingual opening of
the posterior fossettid. This feature is commonly
observed in the m2 and m3, but it also occurs frequently


in the ml in early wear stages. This posterolingual
opening is created by the failure of the posterior horn of
the hypoconid to join the entoconid. This suggests that
pseudoceratine lower molars developed their hypsodont
condition prematurely, as it were, from primitive ruminant
stock in which the hypoconid was still conical.
The protoconid and hypoconid each present more
angular labial faces than in Gelocus or Tragulus. No
accessory folds, such as found in Tragulidae (especially
Dorcatherium) or Palaeomerycidae, occur in the
Pseudoceratinae. A strong protostylid (anterolabial
cingulum) rises steeply from the anterolabial surface of





Webb, S.D.: Revision of the Extinct Pseudoceratinae


the protoconid and persists into moderately advanced
stages of wear. In Tragulidae, on the other hand, it is
weak and ephemeral. The median ectostylid is tall and
well developed on the first two molars but is weak or
absent on the m3. The tip of the ectostylid has nearly
the same height as the hypoconid; in later wear stages
it may be incorporated with that cusp, thereby adding
an anterolabial fold to its normal curve (see ml in Fig.
3C). No hypostylid (posterolabial cingulum) occurs, in
contrast with the condition often observed in Tragulidae.
The m3 differs from the ml-m2 mainly in the
presence of a third lobe. In Pseudoceratinae, this lobe
consists of a simple subcircular loop of enamel (the
hypoconulid) attached to the posterior wall of the
hypoconid labially and, at a much lower level, to the
entoconid lingually. In early wear stages, this heel
appears to be made of two weakly joined enamel
segments, one lingual and one labial. Even in later wear
stages a posterior sulcus may be seen, seemingly
representing a line of fusion between these two portions.
There are never two concentric enamel walls as in
Moschus, Cervidae, and higher ruminants. In the simple
structure of the third lobe of m3, the Pseudoceratinae
resemble other Gelocidae, especially Prodremotherium.
The deciduous lower incisors and canines are not
represented in any known pseudoceratines.
The third and fourth deciduous lower premolars
are present in an unworn stage in UF 17416. A broken
alveolus in this same jaw represents dp2 and suggests
that its length is about 4. The dp3 measures 5.5 long
and 1.9 wide. It is distinguished from p4 only by its
lower crown and by its less complete metaconid blade.
This tooth generally resembles that of other gelocids
(Geraads et al. 1987) and differs markedly from the
long three-cusped dp3 oftragulids.
The dp4 has the long three-lobed structure
characteristic of all artiodactyls. It is 9.1 mm long and
3.1 wide. The two posterolingual cuspids form strong
crescents but the anterolingual cuspid is weak posteriorly.
Likewise the anterolabial cuspid is weaker than the two
more posterior labial cuspids. The posterior edges of
all three labial cuspids flare outward preventing complete
connection with the opposing lingual crescents. In this
respect dp4 resembles the peculiarly primitive structure
of the permanent molars of pseudoceratines.

MANDIBLE
The horizontal ramus is long, about as shallow as
in most cervoids, and bowed upward. Its depth
decreases gradually from a maximum below the last
molar to a minimum beneath the diastema (Fig. 4). The


masseteric fossa is shallow but nonetheless distinct. Its
outline is subtriangular with the anteroventral apex below
and just behind the end of the last molar. This apex is
distinguished by a strong tuberosity for insertion of the
principal tendon of the deep masseter muscle. Beneath
the masseteric tuberosity the jaw becomes shallower,
producing a ventral concavity as in most giraffoids and
cervoids. Behind this, the masseteric insertion occupies
a large semicircle; the jaw deepens and the ventral edge
becomes correspondingly convex. On the ventral and
posterior margins of the masseteric insertion area is a
distinct peripheral muscle scar for the superficial
masseter.
The mandibular condyle lies 10 to 15 mm above
the cheek tooth row. Its neck turns media so that the
condyle lies entirely medial to the plane of the rest of
the ascending ramus, as in higher ruminants but in contrast
to the Tragulidae.
The condyle is remarkably narrow with a
transverse diameter of only 7.0 mm and anteroposterior
diameter of 0.5 mm. The articular surface is nearly
flat. In Tragulidae, by contrast, the condyle resembles
a transversely oriented hemicylinder with a convex
articular surface and a width fully twice the length. The
coronoid process rises in atall graceful curve posteriorly
and slightly laterally to a point about 20 mm above the
condyle. The process tapers somewhat toward its dorsal
tip.

AXIAL SKELETON
The atlas (Fig. 6A) broadly resembles a small
version of an atlas of a cervid such as Odocoileus.
The most notable difference is the convex outline of the
lateral wings, in contrast with the straight margins in the
larger cervid specimens. The axis (Fig. 6B) falls within
the same progressive morphological stage ascribed by
Webb and Taylor (1980) toMoschus and the Cervidae.
This includes full development of the odontoid process
into a subcircular "spout", and dorsal expansion of the
adjacent atlantal articulation almost equal to the top of
the neural canal. In UF 13828 the hatchet-shaped dorsal
crest is about 28.8 mm long and the articular length of
the centrum is 38.5, making the axis the longest cervical
vertebra. The intermediate cervicals are of moderate
length, ranging in length from about 28 to 30 mm along
their centra. The seventh cervical (Fig. 6C) is shorter
(25.2 mm long) and more robust. It has a short,
posteriorly directed neural spine.
Figures 6D and 6E illustrate representative anterior
and posterior thoracic vertebrae, respectively. A
relatively small (presumably young) thoracic from the





BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(2)


3 cm
Figure 6. Left lateral views of A, UF 225937, atlas; B, UF 225938, axis; C, UF 225950, seventh cervical vertebra;
D, UF 226233, anterior thoracic vertebra; E, UF 226234, posterior thoracic vertebra; and F, UF 226236, lumbar
vertebra of Floridameryx floridanus from the Withlacoochee River 4A Site.


middle of the series, UF 225920, indicates that the neural
spines were relatively tall in Floridameryx. Although
its centrum is only 13.1 mm long, the spine reaches 41
mm above the top of the centrum. The spine slopes
posterodorsally at an angle of about 25 degrees from
the plane of the neural canal.
The lumbar vertebrae (Fig. 6F) show a remarkable
range from narrow centra near the anterior end of the
series to very broad specimens representing the posterior
end of the series. For example the widths of some
anterior lumbar centra measure about 12 mm, whereas
in UF 226236 the width is 16.5 mm. The maximum
widths of the free transverse processes range between
50 and 52 mm. The zygapophyses of the lumbars are
very tightly curled inward indicating strong defense
against dislocation by hind limb thrusts during leaping or
galloping.
The sacrum (Fig. 7) has even broader centra. For
example, in UF 24173, the anterior width is 19 mm. In


that individual the sacrum is made up of four fused
vertebral segments, but in others there are five. The
sacrum narrows rapidly toward the tail, so that the
posterior segment in UF 24173 is only 12 mm wide and
11 mm high. It arches downward and the neural canal
becomes minute suggesting a fairly short tail. Various
caudal elements are preserved, but there are not enough
to give a sense of the overall proportions.

FORELIMB
Measurements of the major forelimb elements are
provided in Table 2 and they are illustrated in Figure 8.
The scapulais about 80 mm long, and the anteroposterior
dimension of the glenoid cavity is 17 mm. The humerus
is relatively stocky (Fig. 8B-C). The olecranon process
of the ulna (Fig. 8D-E) adds another 16 mm to the
functional length of the forelimb. In a sample of more
than a dozen well-preserved radioulnae, only two, UF





Webb, S.D.: Revision of the Extinct Pseudoceratinae


I-
/


5 cm


Figure 7. A, lateral and B, anterior views of UF 225981,
sacrum of Floridameryx floridanus from the
Withlacoochee River 4A Site.


18954 and 18955, had the ulna associated with the
proximal end of the radius. The former of these had
exostoses that artificially prevented separation. The
shaft of the ulna was evidently very frail but extended
the complete length of the radius, as indicated by


Table 2. Comparative measurements of forelimb (in mm).
proximal width


attachment scars along the posterolateral face of most
radii, and its distal end did not fuse with the radius.
The third and fourth metacarpals are fully fused
into a cannon bone (Fig. 8F-G) even in young individuals
with unfused distal epiphyses. The distal keels extend
fully (180 degrees) from the anterior to the posterior
face of each metacarpal. An anterior groove is evident
on all specimens, although it becomes very faint on the
most mature individuals. About 7 mm from the distal
midline, a small foramen enters a closed gully (Fig. 8F).
At the proximomedial end of the metacarpus on the
plantar surface a triangular facet about four mm on each
side represents a vestigial second metacarpal.
The proximal surface of the third metacarpal gives
credible evidence that the trapezoid and magnum are
fused in Floridameryx. Careful examination of the
medial side of that articulation on all available specimens
shows no line of separation, encouraging the presumption
that this fusion was present as in most ruminants. Direct
evidence of the smaller carpal elements are missing in
the Withlacoochee River sample, because the skeletal
material is not articulated, and the smaller elements were
seldom recovered in the underwater excavations.
The phalanges of Pseudoceratinae are those of
an ordinary, small, cloven-hoofed ruminant. The few
such elements available in this collection do not allow


DW, distal width; L, length; OL, olecranon length; PW,


Floridameryx floridanus
With. 4A


L
79.1
1.8
15


L
98.2
4.1
13


L
97.9
2.0
14


PW
16.3
3.1
15


PW
15.8
0.6
18


PW
13.2
0.4
20


Gelocus communis*
Ronzon


DW
17.0
0.7


DW
15.3
0.8
15


Bachitherium cf. : ,t ''
Cereste

L
146

1


L
141


* after Geraads et al. (1987, p. 64)


Humerus
x
s
n


Radio-ulna
x
s
n


Metacarpal
x
s
n





BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(2)


A B C
S/


I! '1!











D E

























A, UF 17403, left scapula; B, anterior and C, lateral views of UF 13827, left humerus; D, anterior and E, lateral views
of UF 18955, left radioulna; and F, anterior and G, posterior views of UF 226038, left metacarpus.
I, .. 1///














ofUF 18955, left radioulna; and F, anterior and G, posterior views ofUF 226038, left metacarpus.






Webb, S.D.: Revision of the Extinct Pseudoceratinae


3 cm


- \





/

^ /


Figure 9. Lateral view of UF 201847,
Site.


left pelvis of Floridameryxfloridanus from the Withlacoochee River 4A


Table 3. Comparative measurements of hind limb (in mm). DW, distal width; L, length; PW, proximal width.


Floridameryx floridanus
With. 4A


L
116.9
4.3
7


L
134.2
3.8
15


L
103.3
3.0
26


PW
26.4
1.4
11


PW
25.5
2.7
23


PW
13.5
0.5
36


Gelocus communis*
Ronzon


DW
22.8
2.8
12


DW
17.0
0.6
24


DW
15.0
0.6
34


Bachitherium cf. :,ig,"
Cereste

L
184


* after Geraads et al. (1987, p. 64)


us to distinguish between those of the
feet.


fore- and hind


HIND LIMB
Measurements of the major hind limb elements
are provided in Table 3 and they are illustrated in Figures


9-12. The pelvis (Fig. 9) represents a relatively
progressive stage of ruminant locomotor evolution. Its
overall length can be estimated as greater than 100 mm,
based on various well-preserved anterior and posterior
portions. The iliac blade is well expanded in proportion
to the blade connecting it to the acetabulum, the former


Femur
x
s
n


Tibia
x
s
n


Metatarsus
x
s
n








A ; B C D E.








I ,' I I




/ I







Figure 10. A, anterior B, posterior, and C, lateral views of UF 226095, left femur; and D, lateral and E, anterior views of UF 18956, left tibia of Floridameryx 0
floridanus from the Withlacoochee River 4A Site.





Webb, S.D.: Revision of the Extinct Pseudoceratinae


having a diagonal expanse of about 40 mm and the latter
a minimum dorsoventral diameter of only about 12 mm
in UF 13819, a mature left pelvis. Directly dorsal to the
acetabulum and posterior to the greater sciatic notch is
a widely convex region more than 15 mm deep, featuring
strong tendinous scars for the ischial musculature, most
importantly a powerful M iliopsoas. Despite its small
scale this region closely resembles the homologous area
in Odocoileus and other progressive cervids. The
functional significance of these features will be
considered further below.
The femur (Fig. 10A-C) and tibia (Fig. 10D-E)
are gracile, not unlike those of a miniature cervid. Five
examples of the patella are known in Floridameryx.
Each has a tear-drop shape and measures about 18 mm
long, 13 mm wide and about 8 mm thick near the proximal
end. Other than their shorter proportions the patellae
broadly resemble those of Moschus and the Cervidae.
The fibula is represented at its proximal end by a
vestige of bone extending distally from the posterolateral
corner of the tibia (Fig. 10E). In several individuals it
forks into two processes ofwhich the more lateral attains
a length of 7 to 9 mm. The distal end of the fibula, as in
most other ruminants, forms a malleolar bone that forms
a sliding articulation with the calcaneum, and lodges on
its medial side in a notch on the distolateral corner of
the tibia. The stages of its transformation within hornless
ruminants were discussed by Webb and Taylor (1980).
In Floridameryx, the distal fibula is only known by two
examples, but its morphology and function are readily
inferred from the corresponding surface of the
calcaneum. That articulation consists of a relatively
large proximal convexity and a very small distal surface
that is nearly flat. The corresponding surface of the
malleolar bone has not progressed to the fully concavo-
convex pattern of cervids and other progressive
ruminants. It more closely resembles the transitional
arrangement in Gelocus.
The metatarsus (Fig. 11) is fully fused except in a
few specimens that are presumably fetal. At the proximal
end on the plantar face, a small rugosity on the lateral
side and another more prominent one on the medial side
probably represent the vestigial fifth and second
metatarsals respectively. These proximal rudiments are
smaller than those in Leptomeryx (Webb & Taylor
1980:144). The line of fusion between the third and
four metatarsals leaves a deep groove on the anterior
surface of the metatarsus which enters a closed gully 6
to 8 mm above the base of the distal epiphyses (Fig.
11A). At the point where the groove enters the "gully
foramen" it is nearly 2 mm in diameter. In juvenile


-IJ





1111q


B

N ~


~ II I


II I I
III I
I.

II









I' ~

II ir
III' liIi ii
\II!


Figure 11. A, anterior and B, posterior views of UF
226164, left metatarsus of Floridameryx floridanus
from the Withlacoochee River 4A Site.

specimens lacking distal epiphyses the gully has not been
fully bridged. As in the metacarpus the distal articulations
of the metatarsus in adult specimens are strongly keeled.
The cubonavicular bone (Fig. 12A-B) is fully fused
and has the proportions typical of advanced ruminants.
The astragalus (Fig. 12C-E) is parallel-sided and short-
coupled (nearly cubic) as in progressive pecorans (Webb
and Taylor 1980). The one probably primitive feature
of the astragalus (and calcaneum) is the narrowness of
the sustentacular surface. In contrast with Moschus
and most Cervidae, this surface does not extend medially
beyond the rest of the bone. Presumably the expanded
sustentaculum in more advanced pecorans is an
adaptation for greater support of the foot especially
during leaping and galloping. The only non-pecoran
feature of the calcaneum (Fig. 12F-H) concerns the
articulation for the malleolar and has been discussed
above.

LOCOMOTOR ADAPTATIONS
The limb proportions of Floridameryx can be seen
in Tables 2-4. In 1972 my laboratory assistant, Chandra





BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(2)


C



( '*



F



)I


P 11
'<"/ i '*



b- .


-y
~ ;'~4 \
1.




H -~







'~~
.1


Figure 12. Tarsal elements of Floridameryxfloridanus
from the Withlacoochee River 4A Site. A, proximal and
B, distal views of UF 226197, left cubonavicular; C,
medial, D, anterior, and E, lateral views of UF 226185,
left astragalus; and F, medial, G, anterior, and H, lateral
views of UF 226176, left calcaneum.

Aulsbrook, and I assembled a composite skeleton (UF
201847) from the Withlacoochee River 4A collection.
From that skeleton, now on exhibition in the Hall of


Table 4. Limb proportions in Floridameryx floridanus


Florida Fossils at Powell Hall on the UF campus, one
gets a much clearer general impression of the nature of
this animal (Fig. 13). Striking features of this skeleton
are the two nearly equal pairs of long, straight limbs and
the long, straight back. It looks, in other words, much
like a small deer, and much less like Tragulus, a mouse
deer. The latter have short forelimbs, tucked-up hind
limbs, and strongly flexed backs, producing a posture
much like that of a rabbit. I return to a fuller discussion
of this point in another section below.

RELATIONSHIPS
The Pseudoceratinae are a rare and relatively short-
lived group of homeless ruminants. On the basis of present
records, they are confined geographically to North and
Central America. The subfamily exhibits a puzzling ar-
ray of primitive and progressive characters. The up-
right lower canine in male mandibles suggested to Frick
(1937) affiliation with Tylopoda rather with Ruminantia.
On the other hand, many progressive features of the
skeleton, such as keeled metapodials and front limb
length nearly equal to hind, suggest comparison with
homed or antlered ruminants. The balance of osteo-
logical evidence indicates something in between, namely
that Pseudoceratinae fall within the homeless Pecora.
Now that the osteology of Pseudoceratinae has
been described, its resemblance to Tylopoda may be
recognized as retained primitive (plesiomorphous) char-
acters. For example, an upright lower canine is com-
mon to most mammals. It is modified in special ways
among various derived lineages, including most of the
Ruminantia.
Pseudoceratinae share many derived characters
(synapomorphies) with the Ruminantia. Prominent ex-
amples of ruminant synapomorphies are absence of upper


Percentage is the mean length of each individual limb


element divided by the sum of the means of the three elements for that limb in Tables 2 and 3.


Forelimb
Humerus
Radioulna
Metacarpus


Hind Limb
Femur
Tibia
Metatarsus


Percent
28.7
35.7
35.6


Percent
32.9
37.9
29.2


Fore/Hind Ratio
































Figure 13. Composite mounted
skeleton of Floridameryx floridanus,
UF 201847, from Withlacoochee River
4A collection, on permanent public
display at the Florida Museum of .
Natural History. Skull is a cast of the I
specimens in Figure 1; a few other
elements are either casts or restored,
but most of the postcranial skeleton is
original fossil material.d































Figure 14. Cladogram of lower Pecora, modified from
Geraads et al. (1987). Synapomorphies at numbered
positions on the cladogram: 1) narrow posterolateral
exposure of mastoid; DP3 with strong lingual cingulum;
talonid of dp3 complex; strong metaconid on lower
premolars; lateral metapodials incomplete or absent;
astragalus parallel sided. 2) fibular facet ofcalcaneum
convex. 3) simple p 1. 4) caniniform p 1; C 1 with strong
crest; proximal end of metatarsals nearly circular. 5)
elongate odontoid process; crescentic protocone on up-
per premolars; p absent; increasing hypsodonty with
cementum on cheek teeth; metacarpals fused;
metapodial keels complete; astragalus cubic. 6) lower
premolars with posteriorly directed metalophids. 7) su-
praglenoid foramen present; upper canine flattened and
sigmoidal; limbs elongate with forelimb length nearly
equal to hindlimb length. 8) metalophid on lower
premolars; p4 with four strong lingual crests; lower
molars with closed trigonids. 9) elongate facial region;
lacrimal fossa for facial gland; upper canines reduced;
Palaeomeryx-fold on lower molars.

incisors; fusion of trapezoid and magnum in the carpus;
and fusion of cuboid and navicular in the tarsus. Also it
is evident that Pseudoceratinae lack cranial appendages
and thus lie basal to the higher Pecora, including the
great diversity of homed, antlered, and ossiconed rumi-
nants.
The first cladogram to present an hypothesis about
interrelationships of lower ruminants was by Webb and


BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(2)

Taylor (1980). Above Tragulina, they placed Gelocidae
and Moschidae as the basal families of Pecora. The
second such cladogram was produced by Geraads et
al. (1987:fig. 45). It added many significant compari-
sons among the Neoselenodontia. Its special feature
was a detailed phylogenetic arrangement of the genera
Gelocus, Bachitherium and Prodremotherium. The
part of their cladogram representing the relationships
among hornless Pecora is adopted here (Fig. 14). In
this edition, however, Pseudoceratinae are inserted just
above Gelocus and Bachitherium, and just below
Predremotherium. The branch points, presented in this
figure caption, have been renumbered. Many of the
morphological features (synapomorphies) assigned to
the branch points are direct translations of the original
evidence provided by Geraads et al. (1987). This pro-
vides a phylogenetic framework for Pseudoceratinae,
and explains why it is appropriate to assign this subfam-
ily to the family Gelocidae.
Inflation of the genus Bachitherium to its own
family within Tragulina was proposed by Janis (1987)
after Geraads et al. (1987) was in press. This awk-
ward timing explains the inability of the latter paper to
comment upon the former. In this cladogram (Fig. 14),
the close affiliation of Gelocus and Bachitherium do
not warrant a family distinction for the latter.
Gelocus communis from the early Oligocene at
Ronzon, near Le Puy in southern France, provides a
fundamental reference point in the evolution of hornless
ruminants. In his classic work on Gelocus, Kowalevsky
(1876) documented many key points that placed it near
the ancestry of higher ruminants. Gelocus and several
closely related genera range from the Lutetian through
Aquitanian in Europe and also occur in Asia and Africa
(Hamilton 1973; Vislobokova & Daxner-Hock 2002).
In view of the considerable gap in space and time be-
tween early Oligocene Gelocus in Eurasia and late
Miocene to early Pliocene Pseudoceratinae in North
America, it is not surprising that many intervening steps
remain obscure.
In interpolating the Pseudoceratinae into this phy-
logeny we begin with the basicranial region, then re-
view some general aspects of the dentition, and finally
look at key features of the postcranial skeleton. In the
basicranuium most features of the Pseudoceratinae
broadly resemble those of Gelocus and are consider-
ably advanced over those of the Tragulidae (Fig. 15).
Most obvious are the greater width of the basioccipital
and the breadth across the otic capsules. The square
shape of the glenoid fossa with a prominent postglenoid
process is another synapomorphy shared by Gelocus,





Webb, S.D.: Revision of the Extinct Pseudoceratinae


A


5 cm

Figure 15. Basicranial sketches of A, Tragulus
javanicus and B, Floridameryxfloridanus (UF 19257).

Pseudoceratinae, Moschidae and Eupecora (higher ru-
minants).
Several synapomorphies shared by Gelocus,
Bachitherium, Pseudoceratinae and Prodremotherium
may be noted in the ear region. The anteromedial rim
of the periotic is thickened and broadly fused with the
squamosal. The internal carotid artery was wholly aban-
doned, whereas in Tragulidae a major branch of that
artery ascends along the medial wall of the bulla. In
Gelocidae, the tensor tympani fossa is continuous with
the epitympanic recess and is separated by a crest from
the more posteriorly placed opening of the facial canal.
In Tragulidae, by contrast, the tensor tympani fossa is
continuous with the facial canal opening (Webb & Tay-


lor 1980). The external auditory meatus is tubular and
rises almost vertically to the level of the zygaomatic
arch in Gelocidae and most Pecora, whereas groups
lower on the ruminant tree have the external auditory
meatus lower and more posteriorly directed. The mas-
toid exposure lies along the lateral edge of the occipital
in Gelocidae, including Pseudoceratinae, and most
pecoran ruminants, whereas in Lophiomeryx,
Hypertragulidae and Tragulidae it is larger and extends
anteriorly along the lateral wall of the skull.
Viret (1961) emphasized the diagnostic value of
the anterior cheek teeth in clarifying phylogenetic rela-
tionships among hornless ruminants. In Gelocus, p is
a small premolariform tooth in continuity with the cheek
tooth series. The dpi in Floridameryx has the same
relationship. The fact that pI is subsequently lost in
various ruminant families may diminish its significance,
for it is probably a plesiomorphous feature among
Gelocidae. It is noteworthy that even a few higher ru-
minants, for example the giraffoids Propalaeoryx and
Heterocemas retain a simple p (Hamilton 1973), as in
Gelocus. Bachitherium has autapomorphically en-
larged the p so that it occludes against the posterior
face of the upper canine. Geraads et al. (1987) cor-
rectly describe this as a caniniform first lower premo-
lar. The loss of pI is a feature shared by
Prodremotherium and Pseudoceratinae.
In the almost bladelike lower premolars of Gelocus
one can recognize the antecedents of lingual structures
that become more important later. The paralophid,
metalophid, and posterolophid, and also the faint
hypolophid, are overshadowed by the high anteroposte-
rior slopes of the protoconid. The lower premolars of
Pseudoceratinae exhibit the same basic pattern as in
Gelocus except that the degree of transverse compres-
sion is considerably exaggerated. The long metalophid
and transverse compression of the lower premolars
present striking resemblances between Pseudoceras,
Floridameryx and Bachitherium. In Prodremo-
therium, the lower premolars are shorter, flatter
crowned, and the lingual lophids longer than in Gelocus,
indicating that it had progressed one step farther to-
ward the lower premolar morphology of Dremotherium
and other Eupecora.
The presence of upright lower canines in presumed
male Pseudoceratinae provides an important clue to the
phylogeny of lower ruminants. Presumably this char-
acter state is primitive, as it occurs throughout other
groups of artiodactyls and in other orders of mammals.
If an upright lower canine had been lost and only later
reacquired in Pseudoceratinae, it is unlikely that it could







have regained its precise occlusion with the anterior face
of the upper canine. It seems more likely that this is a
retained primitive character. If so, it places definite
constraints on the phylogenetic position of
Pseudoceratinae within lower ruminant phylogeny.
The following sequence of adaptive changes in
the arrangement of the lower canine in the history of
lower Pecora may be inferred. An incisiform lower
canine was acquired in females very early in ruminant
history. This adaptation for improved food-gathering
evidently coincided with reduction of the upper incisors
and development of an upper cropping pad. Meanwhile,
in males an enlarged upper canine had developed and
was used both for defense of the herd and in intraspe-
cific combat. In its primitive mode it occluded anteri-
orly with the lower canine and posteriorly with the p 1.
In the common ancestor of the Tragulidae and
Hypertragulidae, however, the lower canine in males
became incisiform as in females. Then, in
Hypertragulidae, the p strengthened its occlusal rela-
tionship with the enlarging upper canine; whereas, in
Tragulidae, an increasing diastema isolated the upper
canine from the p I, which retained its primitive form.
Meanwhile, the primitive dimorphic lower canine condi-
tion continued in the common ancestors of the Moschidae
and the Pseudoceratinae. Probably as the canines took
on a more important role in male behavior and breeding
success, they were further enlarged and their self-sharp-
ening mode of occlusion refined. On the other hand,
within the evolution of the Moschidae the male upper
canine became so greatly enlarged that its occlusion
with the lower was difficult to maintain. At this point in
the phylogeny, an upright lower canine became disad-
vantageous and selection for an incisiform (female-like)
lower canine became intense. Also, at this point, the
long upper canine became loose-socketed, a condition
that is retained in tusked Cervidae (Janis & Scott 1987).
Today an incisiform lower canine occurs in all living
ruminants, both male and female.
This proposed sequence of events in the evolution
of pecoran canines requires further evidence before it
can be fully accepted. Gelocus itself could provide
crucial evidence, but at present the exact nature of its
canines is not well documented. Insofar as they are
known, the lower canines appear to be incisiform, but
since, to this author's knowledge, only two mandibles
with alveoli are known, they may both represent fe-
males. Filhol (1877) attributed to Gelocus communis
some upper canines each with a strong wear facet on
its anterior face, and he figured one example. If this
attribution is correct, it constitutes indirect evidence that


BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(2)

some (presumably male) Gelocus had caniniform lower
canines. Several other genera from the Phosphorites
of Quercy, including Lophiomeryx, Bachitherium and
Prodremotherium, consistently have incisiform lower
canine teeth. Likewise Dremotherium shares the
incisiform condition of the lower canine with Eupecora.
In summary, retention of an upright lower canine in male
Pseudoceratinae must be an ancient feature, possibly
shared with Gelocus, and one that is quite anachronis-
tic by late Miocene time.
The lower molars of Pseudoceratinae are narrow
("transversely compressed") with strong metastylids as
in Prodremotherium, as noted by Geraads et al. (1987).
A Palaeomeryx-fold in lower molars is not usually
present in Pseudoceratinae, but is shared by
Prodremotherium and many higher pecorans (Geraads
et al. 1987).
Finally we turn to the postcranial evidence of
Pseudoceratine to shed light on its affinities. In many
postcranial features Pseudoceratinae fall somewhere
among the more progressive Gelocidae or even parallel
with the Moschidae. For example, the metapodials of
Pseudoceratinae are fully keeled and fused at an early
stage of development, about as in Dremotherium. The
second and fifth metatarsals are reduced to minute ves-
tiges, thus advanced well beyond the condition described
by Kowalevsky (1876) in Gelocus communis. The
metapodials are also longer than in Gelocus (Tables 2-
3).
The presence of a closed gully at the distal end of
an anterior groove on the metatarsus has important phy-
logenetic significance as established by Leinders and
Heintz (1980). It is evidently a synapomorphy of
Cervidae, Dromomerycidae and Antilocaprinae. The
absence of a metatarsal groove and gully inMoschus is
also a derived condition, possibly representing a
synapomorphy with Bovidae. Thus the presence of a
deep metatarsal gully in adult Pseudoceratinae implies
an affiliation with probable pre-cervoid stock within
Gelocidae.
Kowalevsky (1876) properly emphasized the im-
portance of locomotor adaptations to properly under-
standing the phylogeny of hornless ruminants.
Tragulidae, with their short limbs and short distal limb
proportions, progress by hare-like leaping. Some of the
principal anatomical correlatives of this locomotor style
include relatively short, broad forefeet, primarily for land-
ing and turning rather than for leaping; high head car-
riage with strong cervical dorsiflexion; a flexible, arched
lumbar region; an underslung pelvis; a deeply flexed,
spring-like hindlimb; and relatively strong version of





Webb, S.D.: Revision of the Extinct Pseudoceratinae


the hind foot (Gambarian 1974; Hildebrand 1985). A
traguloid mode of locomotion was evidently character-
istic of most small artiodactyls in the early Cenozoic.
For example, Hurzeler's (1937) description of
Cainotheriidae emphasizes many features that are both
leporid-like and tragulid-like.
Gelocidae span a considerable variety of transi-
tional forms toward a longer-limbed, straight-backed
pecoran stature. Their morphology and proportions in-
dicate progressive adaptation for fast gaits with extended
suspension, such as the rotary gallop of a deer. Such
gaits in ungulates have been analyzed by Gambarian
(1974) and Hildebrand (1985). The simplification ofthe
joints in feet, especially in the forelimbs, are toward
simple hinge-like mechanisms that are restricted to fore-
and-aft motion. The fundamental reason, as noted by
Hildebrand (1985:43), is that "The faster a quadruped
moves, the smaller its base of support can be." The
loss of side toes and reduction of the ulna and fibula are
clearly aspects of this general trend. Coupled with the
obvious trends in fore- and hind limbs, one also sees
advances in the axial skeleton and especially the pelvis.
The deep ischial region above the acetabulum and the
greatly expanded ilia indicate powerful iliopsoas muscles
for deer-like leaping. In such features, described above,
Pseudoceratinae have progressed beyond Gelocus it-
self, and are comparable with the more progressive
Gelocidae, or even the Moschidae.
Limb proportions in Pseudoceratinae also fall
somewhere in the midst of the complex progression of
Gelocidae and Moschidae. In its forelimb, the radius
and metacarpus of Floridameryx each account for
about 36 percent of the combined
humerus+radius+metacarpus length (Table 4). Equiva-
lent data for a single species of Gelocus are not yet
adequately known. In Fl1,, u,,1, ,y the hind limb pro-
portions, derived in similar fashion, are 38 percent for
the tibia and 29 percent for the metatarsus. In Gelocus
communis the hind limb proportions are 38 percent for
the tibia and 26 percent for the metatarsus, thus retain-
ing a bit more length in the proximal limb segment. In
view of the vast gaps in time and space between
Gelocus communis and Floridameryx floridanus,
these are surprisingly similar proportions, suggesting a
similar stage of skeletal evolution among these lower
pecorans.
The previous descriptions and comparisons indi-
cate that Pseudoceratinae share many special features
with Gelocus. They also share some synapomorphies
(or parallelisms) with Moschidae (and thereby often with
various higher ruminants). It seems reasonable to view


the Pseudoceratinae as a North American clade that
branched from earlier (Oligo-Miocene) Eurasian stock
somewhere within the Gelocidae. An appropriate taxo-
nomic solution, based on the known facts, is to place
the Pseudoceratinae as a distinct subfamily within the
Gelocidae.
Finally, we may ask whether there are any inter-
mediate fossils more closely linking Gelocus from the
Oligocene of Europe and the Pseudoceratinae from the
late Miocene and Pliocene of North America. Two
possible answers deserve brief consideration. One is
the enigmatic genus Bachitherium known mainly from
France. The other involves a pair of poorly known gen-
era from Mongolia.
First, with regard to Bachitherium, it seems clear
that Webb and Taylor (1980) were premature in their
assignment of this genus to the Leptomerycidae, even if
they were correct in wishing to remove it from the pre-
vious assignment to Hypertragulidae (Lavocat 1951;
Viret 1961). Bouvrain and Geraads (1985) announced
the discovery of a skeleton of Bachitherium cf insigne
from Cereste and Geraads et al. (1987) clarified its re-
lationships to other Neoselenodontia. In the same year
Ginsburg and Hugueney (1987) assigned an important
Stampian-aged sample of two species of Bachitherium
to the Tragulidae with a query. Janis (1987:209) con-
sidered Bachitherium, in the progressive nature of the
odontoid process of the axis and in most features of its
postcranial skeleton, "to be at a leptomerycid/gelocid
grade of evolution", and attempted to solve the mani-
fold possible affinities of this genus by placing it in its
own monotypic family, Bachitheriidae.
The lower premolars of Bachitherium are very
distinctive. They have strongly inflected parastylids and
long, posteriorly directed metaconids, the parallel
metaconids and entoconids enclosing long, narrow val-
leys. The left mandibular ramus of Bachitherium in-
signe Filhol, figured and described by Ginsburg and
Hugueney (1987), closely resembles the mandibles with
complete dentitions of Pseudoceras skinneri. Despite
obvious differences in the anterior part of the lower
dentition, with the lower caniniform tooth in
Bachitherium being the lower premolar, but in presumed
male Pseudoceratinae, the lower canine, the two groups
appear closely related.
This cladistic analysis is far from complete, and
much remains to be learned about the flowering of the
Gelocidae. The family remains something of a
"scrapbasket". Besides Gelocus, Bachitherium,
Pseudoceras, Floridameryx and Prodremotherium, it
includes at least a handful of other genera even after







removal of Lophiomeryx to its own family by Janis
(1987). Paragelocus, Pseudogelocus, Phanero-
meryx, Gobiomeryx and Pseudomeryx, for example,
are poorly known osteologically. Nonetheless they hint
at an important evolutionary ferment among lower
Pecora in Eurasia during the Oligo-Miocene.
The genera Pseudomeryx, a possible gelocid, and
Palaeohypsodontus, a possible bovid, both from the
mid-Tertiary of Central Mongolia (Trofimov 1957, 1958;
Vislobokova & Daxner-Hock 2002) might have some
distant affiliation with Pseudoceratinae. In each Mon-
golian form, the lateral compression and precocious
hypsodonty of their molars hint at a similar combination
of primitive and progressive features as in North Ameri-
can Pseudoceratinae. After comparing these two gen-
era with Tragulidae, Gelocidae, and Bovidae, Trofimov
(1957:140) noted that "etaient capable de se nourrir
d'herbes assez dures." Subsequently, one such species
of primitive little ruminants from the Asian steppe might
have reached the central plains of North America in the
middle Miocene, and there extended its tenuous exist-
ence. The extinction of these precocious pecorans took
place first in Asia and later in North America, as the
inevitable pressure of competition from more progres-
sive homed ruminants bore down upon them.

CONCLUSIONS
The subfamily Pseudoceratinae appeared in North
America at the beginning of the Clarendonian land mam-
mal age. Pseudoceras skinneri spread widely through-
out the High Plains, the Gulf Coast, and as far south as
Honduras. Floridameryx, a smaller genus with shorter
premolars relative to its molars, appeared first in the
Round Mountain Quarry, middle Clarendonian of New
Mexico, as Floridameryx klausi, and later as
Floridameryxfloridanus in early and late Hemphillian
sites of Florida. Chronologically the Pseudoceratinae
range from early Clarendonian through late Hemphillian,
a span of about seven million years. They are almost
certainly immigrants to North America, presumably
reaching this continent about 12 million years ago when
they appear abruptly in the record.
Both known genera of Pseudoceratinae appear to
have become extinct by the end of Hemphillian. This
coincides with a very large number of extinctions of
browsing or mixed-feeding ungulate genera in the North
American record (Tedford et al. 1987; Webb et al. 1995;
Janis et al. 2000). These major extinctions at the end of
the late early and latest Hemphillian represent a marked
interval of desiccation at about the end of the Miocene.
If pseudoceratine habitats are correctly interpreted as


BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(2)

stream-border forests, then such desiccation might be
expected to have drastically reduced the living space
and food resources available to them. Thus the seven
million-year history of the Pseudoceratinae ended as
abruptly as it began.
Despite the original assignment of the subfamily
Pseudoceratinae to the family Camelidae, the relatively
complete osteological sample of Floridameryx
floridanus from Withlacoochee River 4A clearly dem-
onstrates the affiliation of this subfamily with homeless
ruminants including Gelocidae and Moschidae from
Eurasia. A surprising arrangement of the lower canines
in which males have upright, self-sharpening fangs, but
females have procumbent incisiform teeth as in higher
ruminants, suggests that such dimorphism may have been
present in other taxa (possibly Gelocus and
Bachitherium) during the Oligocene and early Miocene
ascent to higher ruminants.

ACKNOWLEDGEMENTS
The key to an increased understanding of the
Pseudoceratinae was the discovery and excavation of
Site 4A beneath the Withlacoochee River. For this I
wish to thank the many colleagues, students, and friends
who have assisted in our underwater collecting. The
initial reconnaissance that led to this discovery was con-
ducted by RobertAllen, Norm Tessman, and Kent Ainslie
and was supported by a grant to me from the National
Geographic Society. Subsequent field work was under-
written by the National Science Foundation. Among
the principal divers were Howard Converse, Ben Waller,
Don Serbousek, Graig Shaak, and myself. Altogether
the site was excavated for a total of about one month
each year (except 1972) from the time of its discovery
in May 1967 through May 1974.
My studies of the Pseudoceratinae have benefited
from the advice and courtesy of many colleagues. From
the outset Beryl Taylor of the Frick Laboratory, Ameri-
can Museum of Natural History (New York), freely of-
fered his excellent help and advice. Indeed, it was he
who first recognized that the homeless ruminants from
the Withlacoochee River were Pseudoceratinae.
Malcolm McKenna, Dick Tedford, Morris Skinner, and
Ted Galusha, also of the Frick Laboratory, did much to
make my visits there both productive and pleasurable.
Bryan Patterson was a gracious and jovial host during
my visit to the Museum of Comparative of Zoology at
Harvard University (Cambridge, Massachusetts), and
he and Farish Jenkins have loaned specimens from that
museum. Jack Wilson and Ernest Lundelius of the TMM
loaned undescribed material from collections in their





Webb, S.D.: Revision of the Extinct Pseudoceratinae


care. Bob Hunt has generously loaned specimens from
the UNSM. And, my colleagues at the Florida Mu-
seum, Doug Jones, Bruce MacFadden and Dick Franz,
have offered helpful advice and encouragement. I am
especially grateful to Richard Hulbert for his thorough
review and editorial suggestions. This is University of
Florida Contribution to Paleontology Number 600.
In order to investigate the broader phylogenetic
relationships of the Pseudoceratinae, I visited many of
the great natural history museums of Europe during the
year 1972-1973, as a fellow of the John Simon
Guggenheim Memorial Foundation. This sabbatical year
was also partially supported by a Faculty Development
Award from the University of Florida and by a grant
from the National Science Foundation. During this tour
my family and I were cordially received and helped by
many European colleagues, including Tony Sutcliffe, Alan
Gentry, and Roger Hamilton at the British Museum
(Natural History); Professor J.P. Lehman, D.E. Russel,
D. Sigogneau, C. Dechaseaux, L. Ginsburg, and E.
Heintz at the Musee Nacional d'Histoire Naturelle in
Paris; in Lyon by Pierre Mein at the Faculte des Sci-
ences and M. Phillipp at the Musee d'Histoire Naturelle;
Professors R. Lavocat and L. Thaler, J. Sudre, H.
Capetta, and B. Sige at the Universite de Montpellier;
R. Gounot, Director of the Musee Crozatier du Puy;
Professor J. Htirzeler, B. Engesser and M. Heitzman at
the Naturhistorisches Museum in Basel; Professor R.
Dehm, V. Fahlbusch, F. Obergfell, and K. Heissig at the
Institute ffir Palaeontologie in Munich; J. Franzen at the
Senckenberg Natur-Museum in Frankfurt-am-Main;
Professor H. Tobien and F. Neuffer at the Institut ftir
Geologic und Palaeontologie, Johannes Gutenberg
Universitat in Mainz; and Paul Sondaar and H. de Bruyn
at the Institute of Geologie in Utrecht. And finally in
preparation and illustration of this study I have been
ably assisted by Nancy Halliday, Chandra Aulsbrook,
Erika Simons, Cathy Bester, and my wife, Barbara.

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BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(2)


APPENDIX I
The following are all of the major specimens of Floridameryxfloridanus n. gen. and sp. from the Withlacoochee
River 4A site, Marion-Citrus county line, Florida, in the UF collection.
Braincases: UF 13834, 19257.
Frontals, R & L: UF 19258.
Premaxilla: UF 19270.
Premaxillae & maxillae (associated): UF 13833, 13836.
Maxillae: UF 13831,19261-19269.
Mandibles: UF 13832, 17414-17416,19395,225874-225908.
Upper canines: UF 19271-19273.
Lower canine: UF 225911.
Lower third molars: UF 225909-225910.
Atlas vertebrae: UF 225912-225914,225930,225936-225937.
Axisvertebrae: UF225915-225916,225931,225938-225939.
Cervical vertebrae: UF 225917,225932,225940-225953.
Thoracic vertebrae: UF 225918-225921,225933,225954-225968,226233-226234.
Lumbar vertebrae: UF 225922-225929,225934,225969-225980,226235-226236.
Sacra: UF 17401, 24173,225981-225983.
Ribs: UF 13816, 17402.
Scapulae: UF 13820,17403,226052-226064.
Humeri: UF 13827,17406, 18953,225984-225994.
Radioulnae: UF 18954-18955.
Radii: UF 13818,225995-226018.
Proximal ulnae: UF 13817,226019-226030.
Metacarpals: UF 13822,17407, 18951,226031-226051.
Pelves: UF 13819, 17412,226065-226070.
Femora: UF 13821, 17411,27382,226071-226103.
Patellae: UF 13825, 226231-226232.
Tibiae: UF 13815,17410,18956,226104-226130.
Astragali: UF 13824, 17408,226185-226194.
Calcanea: UF 13826,226172-226184.
Cubonaviculars: UF 226195-226197.
Metatarsals: UF226131-226171.
Proximal phalanges: UF 13823,226198-226229.
Distal phalanges: UF 17409, 226230.
Mounted composite skeleton: UF 201847 (includes numerous elements that are not catalogued individually and a
cast of the composite skull made from UF 13834, 13833, and 13836).




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