Table Of ContentTHE FAUNA AND PALEOECOLOGY OF THE LATE MIOCENE MOSS ACRES
RACETRACK SITE, MARION COUNTY, FLORIDA
by
W. DAVID LAMBERT
A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE
UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE
REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY
UNIVERSITY OF FLORIDA
1994
ACKNOWLEDGEMENTS
I would like to express my deep gratitude to Dr. 3.
David Webb, chairman of my committee, without whose support
and guidance this dissertation would have been impossible.
I
would also like to thank the other members of my advisory
committee. Dr. Bruce MacFadden, Dr. Ronald Wolff, Dr.
Crawford Holling, and Dr. John Eisenberg, and Dr. Douglas
Jones for their support and assistance during the course of
this study. Gary Morgan of the Florida Museum of Natural
History provided indispensable help during this study, giving
invaluable advice and assistance on different topics and
endeavors too numerous to list here. This study could not
have been conducted without the skilled and diligent work of
vertebrate fossil preparator Russell McCarty and associated
volunteers like Patrick Hilton, who performed numerous
miracles in converting seemingless hopeless jumbles of bone
fragments into specimens capable of revealing information
about the animals that first owned them. I am indebted to all
those who gave their time and effort in field crews from the
Florida Museum of Natural History collecting Moss Acres
Racetrack specimens; without their hard work, this study
could not have even been contemplated. Of particular note in
this regard are Gary Morgan, Art Poyer, Russell McCarty, and
Erica Siemens, whose cooperation and tolerance made my field
season at Moss Acres Racetrack in the spring of 1991 a great
success. I gratefully acknowledge the time and effort donated
11
by John Claytor, who operated the backhoe used to reopen the
site on a voluntary basis. Great thanks are due to John
Schimfessel the owner of Moss Acres who first brought the
,
presence of fossils at this locality to the attention of the
Florida Museum of Natural History, and then graciously
allowed crews from the museum to work the site over the
course of years. Similarly great thanks are also due to Linda
and David Markgraf, who as later owners of the Moss Acres
property allowed the site to be reopened with heavy machinery
and the subsequent field work to occur. Laurie Walz created
all specimen illustrations presented in the chapter on the
giant otter Enhvdritherium Dr. Barbara Hansen of the
.
University of Minnesota kindly identified the pollen in the
Moss Acres Racetrack sediment sample. Dr. McCartan of the
United States Geological Survey performed an invaluable
mineral analysis on the Moss Acres Racetrack clays. Both the
University of Michigan and the Smithsonian Institution loaned
me specimens indispensible to this study. The McKenna
Foundation generously provided funds both for field work and
a personal salary for one semester; without its support Moss
Acres Racetrack could not have been reopened in 1991, and
three extraordinary Amebelodon skulls would remain below the
ground undiscovered. The R. Jerry Britt, Jr. Foundation
provided funding for field work via the R. Jerry Britt, Jr.
Paleobiology Award. The University of Chicago Press and the
American Museum of Natural History Press both generously
111
provided me with permission to include copyrighted figures in
this dissertation. Lastly, I wish to express my gratitude to
the Florida Museum of Natural History, which provided me with
access to innumerable and invaluable facilities and personnel
during the conduction of this study; without its help, this
study could not have been accomplished.
IV
TABLE OF CONTENTS
page
ACKNOWLEDGEMENTS
ii
LIST OF COLLECTION ABBREVIATIONS viii
ABSTRACT ix
CHAPTERS
INTRODUCTION
1 1
2 THE GEOLOGY AND AGE OF THE MOSS ACRES RACETRACK
SITE
7
Geology
7
Age
24
A REDIAGNOSIS OF AMEBELODON PROBOSCIDEA,
3
(
GOMPHOTHERIIDAE) AND A NEW SUBGENUS AND SPECIES,
AMEBELODON KONOBELODON BRITTI FROM THE MOSS
( ) .
ACRES RACETRACK SITE
28
Systematics 29
Description 32
The Rediagnosis of Amebelodon 44
Dentinal Rods 50
Biogeography and Chronology 56
4 THE OSTEOLOGY, ECOLOGY, AND PHYLOGENY OF THE
GIANT OTTER ENHYDRITHERITTM TERRAENOVAE 58
Methods 61
Osteology 62
Paleoecology and Functional Morphology 96
Phylogeny 107
5 THE OSTEOLOGY OF THE GROUND SLOTH
PLIOMETANASTES (XENARTHRA, MEGALONYCHIDAE) 116
Materials and Methods 118
Systematics 119
Description 120
The Evolution of Pliometanastes in North
America 155
aq^
u.
6 THE OSTEOLOGY OF PEDTOMKRYX HEMPHTT.T.KN.qT.g
(ARTIODACTYLA, DROMOMERYCIDAE AND THE
)
PALEOECOLOGICAL SIGNIFICAMCE OF DWARFING IN
"^^'E
PEDIOMERYX LINEAGE 159
Materials and Methods 161
Systematics 1S2
Description 163
The Paleobiological Significance of Body Size
Trends in Pedioraervx 177
7 A POPULATION OF APHELOPS MUTIIIS
(PERISSODACTYLA, RHINOCERATIDAE) FROM THE MOSS
ACRES RACETRACK SITE 184
Systematics 184
Osteology 189
Population Ecology 139
Social Structure 198
Diet: and Feeding Mode 203
8 A SUMMARY OF MISCELLANEOUS NON-MAMMAL AND
MAMMAL TAXA FROM THE MOSS ACRES RACETRACK SITE.. 213
Class Chondrichthyes 213
Class Osteichthyes 215
Class Amphibia 215
Class Reptilia 215
Class Aves 224
Class Mammalia 224
9 THE TAPHONOMY OF THE MOSS ACRES RACETRACK SITE.. 239
Data 240
State of Bone Preservation 242
Bone Association 248
Bone Orientation 253
Faunal Biases 256
10 THE PALEOCLIMATE AND PALEOECOLOGY OF THE MOSS
ACRES RACETRACK SITE 263
Paleoclimate 263
Flora 271
Fauna 282
VI
oaae
11 SUMMARY AND CONCLUSIONS 322
rOiOGV - -)
.
Taphonomy 323
Fauna 324
Flora 326
Climate 326
Communi-y Ecology 326
Concluding Remarks 329
APPENDIX 1 A LIST OF POST-CRANIAL ELEMENTS REFERRED TO
AMEBELODON KONOBELODON) 3RITTI FROM THE MOSS ACRES
(
RACETRACK SITE IN THE COLLECTION OF THE FLORIDA MUSEUM
OF NATURAL HISTORY 330
APPENDIX 2 PEDIOMERYX HEMPHTLLENSIS SPECIMENS FROM THE
MOSS ACRES RACETRACK SITE IN THE COLLECTION OF THE
FLORIDA MUSEUM OF NATURAL HISTORY 331
APPENDIX APHELOFS MUTILIS SPECIMENS FROM THE MOSS
3
ACRES RACETRACK IN THE COLLECTION OF THE FLORIDA MUSEUM
OF NATURAL HISTORY 332
APPENDIX 4 FISH, REPTILE, AND BIRD SPECIMENS FROM THE
MOSS ACRES RACETRACK SITE IN THE COLLECTION OF THE
FLORIDA MUSEUM OF NATURAL HISTORY 333
APPENDIX MISCELLANEOUS MAMMAL SPECIMENS FROM THE MOSS
5
ACRES RACETPJVCK SITE IN THE COLLECTION OF THE FLORIDA
MUSEUM OF NATURAL HISTORY 335
APPENDIX 6 HORSE (EQUIDAE) SPECIMENS FROM THE MOSS
ACRES RACETRACK SITE IN THE COLLECTION OF THE FLORIDA
MUSEUM OF NATURAL HISTORY 336
APPENDIX 7 LIST OF SPECIMENS RECOVERED FROM THE MOSS
ACRES RACETRACK SITE DURING THE SPRING FIELD SEASON OF
1991, INCLUDING FIELD NUMBERS, DATE MEASURED, AND A
DESCRIPTION OF SPECIMENS 338
APPENDIX POSITIONAL AND ORIENTATION DATA FOR
8
SELECTED SPECIMENS COLLECTED FROM THE MOSS ACRES
RACETRACK SITE DURING THE FIELD SEASON OF SPRING 1991... 340
LITERATURE CITED 3 41
BIOGRAPHIC SKETCH 55
3
LIST OF COLLECTION ABBREVIATIONS
(OTHER ABBREVIATIONS EXPLAINED IN THE TEXT)
D.M.N.H.: Denver Museum of Natural History, Denver, Colorado
K.U.M. University of Kansas, Lawrence, Kansas
:
MCZ Museum of Comparative Zoology, Cambridge, Massachusetts
:
T.M.M.: Texas Memorial Museum, Austin, Texas
UP: Florida Museum of Natural History Collection of
Paleontology, Gainesville, Florida
UF(M): Florida Museum of Natural History Collection of
Mammalogy, Gainesville, Florida
UM-V: University of Michigan Vertebrate Paleontology
Collection, Ann Arbor, Michigan
UNSM: Nebraska State Museum, Lincoln, Nebraska
USNM(M): Smithsonian Institution Mammalogy Collection,
Washington D.C.
Vlll
Abstract of Dissertation Presented to the Graduate School of
The University of Florida in Partial Fulfillment of the
Requirements of the Degree of Docor of Philosophy
THE FAUNA AND PALEOECOLOGY OF THE LATE MIOCENE MOSS ACRES
RACETRACK SITE, MARION COUNTY, FLORIDA
By
W. David Lambert
April, 1994
Chairman: Dr. S. David Webb
Major Department: Zoology
The Moss Acres Racetrack site represents an early
Hemphillian age, clay-filled sinkhole in western Marion
County, Florida, with a diverse biota, possibly containing
more evidence for local biotic and climatic conditions than
any other late Miocene locality on the Gulf Coastal Plain.
The geology, taphonomy, fauna, palynoflora, and community
ecology of this locality were all examined in this study.
Geological and taphonomic evidence suggests that the
fossil biota was preserved under strictly nonfluvial
conditions in an isolated pond or lake, indicating that this
assemblage represents a real community rather than a mixed-
assemblage. The faunal description included detailed study of
the following mammalian taxa: the gomphothere proboscidean
Amebelodon Konobelodon britti (described as a new subgenus
( )
and species), the ground sloth Pliometanastes (represented by
previously unknown limb elements), the giant otter
Enhvdritherium (represented by a partial skeleton, the best
bunodont otter specimen known) and the dromomerycid ruminant
,
Pediomervx hemohi llensis (including a partial skull with
ix
ly intact horn cores), and the rhinoceros Aoheloos
ilis Other mammal taxa (including the horses) were
mined in a cursory fashion only. Preliminary evidence
gests the presence of a new species of the emydid turtle
udemvs and a new species of Alligator within the
Le
petofauna. The palynoflora revealed a dominance by grass
Y.
oak suggesting a savanna landscape, with all other taxa
:
(map
iividually forming minute portions of the flora. The floral
n
;t resembles that of a modern warm temperate woodland in
in
southeastern United States, suggesting temperatures
-
re
•dlar to those found in the region today. Rainfall patterns
inconclusive, though the presence of a savanna landscape
5
y to
jgests strong seasonal aridity.
nd
The nature of community interactions within the biota
n its
largely inconclusive. Terrestrial carnivores were
3
rtually absent, possibly a result of small sample size,
until
-dence for facilitative grazing like that found in modern
ugh
rican savannas was searched for, with the final results
mg ambiguous. Amebelodon was shown to be a plausible
ological analog for modern African elephants in savannas,
earing woodlands to limit their spread into the grasslands
Lng
i thus encouraging and maintaining biotic diversity.
of
•
i
