Florida Museum of Natural History

Florida Fossil Horse Newsletter

Volume 4, Number 2, 2nd Half 1995

What's Inside?

TBFC Excavates Spectacular 25 million-year-old Florida Fossil Horse Skeleton

During the middle of this year, members of the Tampa Bay Fossil Club (TBFC) excavated a truly spectacular 25-million-year-old Miocene three-toed horse from sediments in Pinellas County. This skeleton was discovered by Chris Skillman, an avid collector who was quick to recognize its importance, and was excavated by a team of volunteers, including: Tony Estevez (field leader), Bob Vander Gronden, Steve Jacobson (TBFC President), Terry Sellari, Frank Kocsis, and Sharon Blinebury.

The specimen is exquisite in its preservation and includes some very interesting details not normally found in Florida fossil horses. First and foremost, this specimen consists of an articulated skeleton, in contrast to most specimens from our region that almost always are represented by isolated and generally fragmentary elements. The details of the specimen are extraordinary--the shiny teeth are beautifully preserved, the large canines indicate that this individual was a male, and even the delicate side-toe splints and tiny side-hooves are preserved (see photo).

Specimen of Miohippus collected by the TBFC. Top: Large canines (arrow) indicate that this individual was a male. Bottom: The two nearly complete limbs flank the complete right and left upper rows of premolars and molars.

Preliminary comparisons of this fossil indicate that it is referable to Miohippus, an extinct genus that is relatively common from the upper part of the Big Badlands and overlying sediments from the High Plains (Nebraska, Wyoming, and South Dakota). These occurrences indicate an age of about 25 million years for the Florida skeleton. Miohippus is exceedingly rare east of the Mississippi River. Taken together there are only a handful of specimens pertaining to Miohippus from the eastern U.S., the others of which include fragmentary teeth and broken bones.

Miohippus is also known (and was first described by the Yale paleontologist O. C. Marsh) from the John Day Fossil beds of Oregon. Determination of exactly which species of Miohippus this specimen represents must await detailed anatomical investigations and comparisons with specimens in other museums.

Studies of the ancient biology of the genus Miohippus indicate that this fossil horse was tiny, weighed about 80-90 pounds, probably lived in small herds, and was a browser, i.e., it fed on leafy vegetation (as opposed to grass). While it certainly was capable of running, it probably did so at a slower pace and for shorter periods of time than the modern horse Equus.

Tony Estevez (right) and Steve Jacobson (left) excavating the Miohippus horse from a creek-bed in Pinellas County.

This wonderful specimen was acquired by the TBFC for exhibition and study and it is intended to be donated to the FLMNH. The generosity of the TBFC and recognition of the importance of preserving this unique and extraordinary specimen in the public/scientific domain is greatly appreciated.

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New VP Collections Manager--Marc Frank

We are delighted to announce that Marc Frank has joined us as Collection Manager in the Vertebrate Paleontology collection at the FLMNH. Marc is a native of Augusta, Georgia. He did his undergraduate studies at the University of Georgia where he received a BA in Anthropology. He then came to Gainesville where he did an interdisciplinary Master's degree (combining zoology and anthropology) studying zooarchaeology with Dr. Elizabeth Wing. (Zooarchaeology is the study of non-human animal remains found at archaeological sites. With these remains archaeologists can better understand the kinds of animals that were consumed, technologies used, and habitats exploited by ancient peoples.) During his graduate studies at UF, Marc served as the teaching assistant in the Vertebrate Paleontology course and also worked in the VP collection during 1990-1991 doing extensive curation of fossil mammals, mostly from the Aucilla River. Between 1992 and mid-1995, when he joined us at the FLMNH, Marc gained extensive museum curatorial experience as a Museum Specialist in the Division of Mammals at the Smithsonian Institution in Washington, D. C. At the FLMNH, Marc's current duties as Collection Manager include handling all sorts of inquiries, arranging for visitors and students to use the collection, public outreach, field collecting, overseeing the curation and conservation of the entire VP fossil vertebrate collection, and supervision of collection staff. We welcome Marc to the FLMNH as a member of the VP collections group.

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The Thomas Farm Fossil Horse Digs--1995

The 1995 Pony Express fossil digs consisted of two sessions held on April 20-23 and May 4-7. The staff for both sessions were: Dr. Bruce MacFadden (leader and cook), Art Poyer ("pit boss"), Bruce Shockey (pit assistant), and Russ McCarty (preparator). Erika Simons joined us in the May session. In addition to excellent digging, wonderful weather, and congenial camaraderie, we were also treated to evening stargazing sessions by raconteur extraordinaire and UF astronomy professor Dr. Howard Cohen.

The Thomas Farm fossil locality was discovered quite by accident in the late 1920s by Florida archaeologists who were doing routine county resource surveys. It was soon realized that this 20 million-year old locality was one of the richest sites dating from before the Ice Age (Pleistocene) in the entire U.S. Since the late 1940s, the Thomas Farm site has been excavated primarily by UF paleontologists and their assistants. The Pony Express has sponsored Spring Digs at Thomas Farm since 1992.

Although we have had excellent success in years past with collecting new and exciting fossils at Thomas Farm, it is safe to say that this years' overall productivity, in terms of both the quantity and quality of fossils, is the best so far. A total of about 15 horse jaws, 2 skulls (including the extraordinarily rare dwarf horse Archaeohippus, see photos), several rare extinct camels, and small deer-like mammals made this dig a truly rewarding experience from a paleontological point of view.

The following is a preliminary list of the fossils thus far identified and catalogued (compiled by Erika Simons and Art Poyer). It by no means reflects the entire spectrum of fabulous fossil finds of the 1995 field season. Many of the skulls still await preparation.

Archaeohippus, lateral (side) and palatal (bottom) views of a very well-preserved skull collected by Jeff Yaun during the 1995 Thomas Farm fossil dig. To the left in each view you can see the nasal (nostril opening) region, and at the bottom, views of the premolar and molar teeth. The eye socket, or orbit, is indicated by an arrow. This specimen was excavated from the site using a plaster jacket, prepared in the lab by Russ McCarty, and catalogued and photographed by Erika Simons.

Jeff Yaun, collector of the Archaeohippus skull, with Liz Anderson (top left) and Barbara Toomey (top right). Photo by Donna Blair.

Session I--APRIL 20-23

Person Name
Sci name
Mary Elizabeth Anderson (Winter Park) Archaeohippus blackbergi cheek tooth, vertebra, radius, carpals, tarsals, distal metapodial, sesamoid, phalanges
Alligator olseni osteoderms
Geochelone tedwhitei costal
Parahippus leonensis right mandible w/cheek teeth, teeth, distal radius, patellae, lateral and medial metapodials, proximal sesamoids, carpals, tarsals, phalanges
Artiodactyla wrist bone, fibula, patella, phalanges
Blastomeryx floridanus left mandible with cheek teeth
Floridaceras whitei sesamoid
Carnivora phalanx, mustelid calcaneum
Canidae left partial mandible
Betsy Carlson (Gainesville)> Archaeohippus blackbergi mandible, humerus, radius
Parahippus leonensis teeth, radius, ulna, tibia, metatarsal, carpals, tarsals, phalanges
Alligator olseni articular, teeth, osteoderms, phalanges
Artiodactyla phalanges
Blastomeryx floridanus astragalus
Carnivora canine
Audrey Carter (Winter Garden) Archaeohippus blackbergi teeth, metapodials, carpals, tarsals, phalanges
Alligator olseni teeth, frontals, osteoderms
Geochelone tedwhitei costals, marginals
Parahippus leonensis teeth, mandibles, vertebrae, carpals, tarsals, metapodials, phalanges
Blastomeryx floridanus cheek tooth
Artiodactyla patella, phalanges
Carnivora caudal vertebra
Melissa Khoshesperan (Altamonte Springs) Archaeohippus blackbergi tibia, tarsal, phalanx
Alligator olseni tooth, osteoderm
Parahippus leonensis radius, proximal sesamoid, phalanges
Carnivora canine
Derk Kuyper (Orlando) Archaeohippus blackbergi mandible fragment, teeth, proximal scapula, femur, tibia, carpals, tarsals, phalanges
Alligator olseni premaxilla, maxilla, vertebrae, teeth, osteoderm
Geochelone tedwhitei neural, marginal
Pseudemys costal, marginal
Parahippus leonensis teeth, vertebrae, femur, pelvis fragment, tibia, tarsals, metapodials, phalanges
Blastomeryx floridanus calcaneum
Artiodactyla tibia, phalanx;
Canidae radius, tarsal
Carnivora tarsal
William Lee (Baton Rouge, LA) Archaeohippus blackbergi incisor, metacarpal, phalanx;
Alligator olseni squamosal, tooth
Reptilia phalanx
Anura limb bone
Parahippus leonensis lunar, sesamoid, phalanx;
Machaeromeryx gilchristensis calcaneum, astragalus
?Rodentia unfused femur
Carnivora premolar, phalanx
Ursidae atlas
Robert Mueller (Gainesville) Archaeohippus blackbergi teeth, mandible with cheek teeth, carpals, tarsals, medial metacarpal, phalanges
Alligator olseni articular, radius, osteoderms
Geochelone tedwhitei costals, shell element
Parahippus leonensis maxilla with cheek teeth, teeth, radius, scapula, femur, carpals, tarsals, phalanges
cf. Anchitherium clarenci occipital condyle
Artiodactyla proximal scapula, tarsal
Mustelidae incisor
Jewel Pozefsky (Altamonte Springs) Archaeohippus blackbergi teeth, sesamoids, patella, metapodials, phalanges
Alligator olseni osteoderms, phalanges
Pseudemys sp. marginal;
Bufo sp. ilium
Parahippus leonensis teeth, scapula, carpals, tarsals, metapodials, phalanges
Blastomeryx floridanus calcaneum
Artiodactyla astragalus, phalanges
Carnivora metacarpal, metapodial
Scott Stuart (Orlando) Archaeohippus blackbergi humerus, ectocuneiform, first lateral phalanx
Alligator olseni osteoderms
Pseudemys sp. neural
Parahippus leonensis proximal scapula, medial metacarpal, lateral metapodials, tarsals, medial phalanges, vertebra
cf. Artiodactyla proximal scapula
Canidae fifth proximal metatarsal
Carnivora distal metapodial
Barbara Toomey (Sanibel) Archaeohippus blackbergi mandible fragment, teeth, humeri, tibia, patella, ulna, radius, carpals, tarsals, metapodials, phalanges
Alligator olseni teeth, osteoderms, vertebra, femur, phalanges
Geochelone tedwhitei costal
Pseudemys sp. costals, marginals, plastron fragments
Bufo sp. ilium
Parahippus leonensis teeth, vertebra, distal tibia, patella, carpals, tarsals, sesamoids, phalanges
Rhinocerotidae ectocuneiform, third metacarpal, innominate
Artiodactyla distal tibia, phalanges
cf. Cynodesmus iamonensis right mandible with molars
Amphicyon longiramus tooth, phalanx
Mustelidae proximal femur
Reed Toomey (Sanibel) Parahippus leonensis 2 right mandibles with teeth, isolated teeth, tibia, calcaneum, metapodials, phalanges, vertebrae
cf. Tomarctus canavus right mandible with premolars and molars
Canidae patella
Ursidae incisor;
Amphicyon longiramus phalanx
Rita Warren (Miami) Archaeohippus blackbergi phalanges
Parahippus leonensis teeth, skull fragment, metapodial, tarsal, phalanges
Blastomeryx floridanus astragalus
Artiodactyla phalanx
Carnivora skull fragment, phalanx
Jeff Yaun (Mayport) Archaeohippus blackbergi skull with complete cheek dentition, teeth, humerus, carpals, tarsals, metapodials, phalanges
Alligator olseni teeth, osteoderms, skull bones
Geochelone tedwhitei costals, marginals
Parahippus leonensis skull with complete cheek dentition, maxilla frag., mandible with complete cheek dentition, teeth, proximal radius, proximal ulna, right innominate, sacrum, patella, carpals, tarsals, metapodials, phalanges
cf. Floridaceras whitei patella
cf. Nothokemas premolar
Artiodactyla radius, carpals, phalanx
Mustelidae calcaneum
Carnivora axis, premaxilla

Session II--MAY 4-7

Person Name
Sci name
William Killingsworth (Leeds, AL) Archaeohippus blackbergi tarsal, phalanx;
Alligator olseni femur, osteoderm
Geochelone tedwhitei marginals
Pseudemys sp. costals, marginal
Parahippus leonensis teeth, vertebrae, scapula, innominate, carpals, tarsals, metapodials, phalanges
Rhinocerotidae left upper P1
Artiodactyla patella
Canidae fibula;
Carnivora metapodial
Derk Kuyper (Orlando) Archaeohippus blackbergi carpals, tarsals, metatarsals
Alligator olseni vertebra, osteoderm, distal tibia
Geochelone tedwhitei costal, hypoplastron
Emydidae vertebra
Parahippus leonensis teeth, carpals, tarsals, metapodials, phalanges, vertebrae, patella
Artiodactyla teeth, astragalus, phalanges
Canidae axis, vertebra
cf. Canidae patella
Carnivora caudal vertebra, phalanges
Wandi Savage (Apopka) Alligator olseni osteoderm
Parahippus leonensis carpal, tarsal, phalanx
Mustelidae radius
Mammalia patella
Judy Thompson (Leeds, AL) Archaeohippus blackbergi incisor, distal radius, carpal, tarsal, lateral metapodials, phalanges
Alligator olseni: tooth, osteoderms
Geochelone tedwhitei neural
Pseudemys sp. epiplastron, tibia
Anura vertebra
Parahippus leonensis incisor, tarsal, metapodial, sesamoids, phalanges
Marcia Wright (Winter Park)- Archaeohippus blackbergi tooth, radius, vertebrae, carpals, metapodials
Alligator olseni tarsal, osteoderms
Geochelone tedwhitei marginals, osteoderm
Parahippus leonensis tooth, vertebrae, radius, patella, femur, carpals, tarsals, metapodials, phalanges
Artiodactyla tooth, patella
Canidae radius
Carnivora radius, premaxilla, phalanx
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Left (top): Reed Toomey. Left (bottom): Audrey Carter (bottom left), Bruce Shockey (top), and Jewel Pozefsky (right). Right: Bill Lee, expert screenwasher and raconteur extraordinaire.

"Local Boy Makes Good"--J. Daniel Bryant

We are pleased to report that J. Daniel "Danny" Bryant, a Florida native, recently received his Ph. D. in paleontology from the Department of Geological Sciences at Columbia University in New York City. His doctoral dissertation involved a study of oxygen in fossil horse teeth to understand ancient climates in the Miocene of North America. Danny spent most of his youth in Lakeland where he early on acquired a love of collecting fossils from the phosphate mines in central Florida. Danny then went on to UF where he received his B. S. in 1988 and M. S. in 1990, both in Geology while also working extensively at the FLMNH. For his Master's thesis Danny worked as one of MacFadden's students and collected Miocene mammals from the relatively poorly known clay mines in the Florida Panhandle and determined the age of these fossil localities using both paleomagnetic and Strontium dating techniques. During his field work, Danny was greatly aided by the help of a local collector, Jim Morris of Bainbridge, GA (In-kind donations).

After receiving his Ph. D. this past summer, Danny began a postdoctoral appointment as a research scientist in the Department of Geological and Geophysical Sciences at Princeton University. We wish Danny the best of luck with his career!

J. Daniel "Danny" Bryant (left) receives his Ph. D. from Columbia University.

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Bone Spotlight--Sesamoids: Those Forgotten Bones, by Dr. John Hermanson

(Editor's note: Dr. John Hermanson is an Associate Professor of Anatomy in the College of Veterinary Medicine at Cornell University, Ithaca, NY. John has a Ph. D. in Zoology from the University of Florida and has collaborated with the Editor on two professional papers dealing with the evolution of upright posture in fossil horses. John is the professor in charge of teaching horse anatomy to each years' new crop of veterinary students. When John is not studying horses, his other research interests include the mechanics of bat flight.)

Sesamoids are small, usually overlooked, accessory bones that frequently fossilize, but are not readily associated with the animals that had them in life (see for example, limb bone with sesamoid bones in illustration). The function of sesamoid bones is not certain, nor is it clear how sesamoids have come to be distributed at various locations of the body in many animals. Clearly, sesamoids are associated with the distribution or redirection of forces within tendons of specific muscles. Of these, the human patella (kneecap) springs most easily to mind. The patella is a bone located within the tendons of the knee extensor muscles. In this location, the patella increases the mechanical advantage (or the force generation) of these muscles in knee movements, an advantage resulting from the displacement of muscle action away from the center of joint rotation.

Horses exhibit a series of fascinating and important sesamoid bones in the limbs and digits. These include the proximal1 sesamoids (see illustration), which are paired and located at the junction of the wrist and fore-limb toes and ankle and hind-limb toes, and the distal2 sesamoids which are single and located between the toe bones (phalanges). Several functions are attributed to these sesamoid bones. For example, the proximal sesamoids form a pulley around the fetlock (anatomically equivalent to the knuckle at the base of your middle finger) joint. But these sesamoids are embedded in the tendon of the interosseous muscle (not really a muscle because no real muscle fibers can be detected in the adult "muscle"- but that's another story!). The anatomy of the proximal sesamoids is similar in both the forelimb and hindlimb. As the weight of the individual is applied to the limb, the fetlock joint yields to the weight of the animal and overextends or "sags." The interosseous muscle is the proximal part of a supporting system called the suspensory apparatus, which incorporates the proximal sesamoids and continues distally as a multi-ligamentous structure. The sesamoidean ligaments perform important roles which prevent overextension (collapse) of the digital joints. In life, the weight of the animal causes movement in these joints which causes the suspensory apparatus to stretch to a point of equilibrium, beyond which further collapse of the joints is not possible.

If you've ever looked closely at the limb posture of horses at the end of a long race, you may note a surprising amount of overextension of the fetlock joint, thought to result from exhaustion of the suspensory apparatus and associated supporting muscles. This is a complicated system and one that is often associated in breakdown at the racetrack, either through overextension of the fetlock and resultant poor placement of the proximal sesamoids (leading to fracture of these important bones), or actual tearing of the proximal bony attachments of associated muscles. As we reflect upon fossil horses and a time before veterinary medicine became adept at repair or prophylactic treatment of the equine athlete, how did the earliest single-toed horses prevail without injury to the digit? Perhaps further investigation of these small bones in fossil horses will shed light on this question and the adaptive value of sesamoids in more modern horses like Equus.

(Right) Side view of horse front foot showing position of proximal and distal sesamoid bones.

1, 2 Proximal and distal refer to anatomical positions that are respectively, closer to, and away from, the main body. In humans the thumb is distal to the wrist and the kneecap (patella) is proximal to the ankle. Also see Pony Express, vol. 1, no. 2, page 8 for discussion of anatomical positions.

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Reader's Forum

...about the Florida Museum of Natural History site on the World Wide Web: "It looks really good. You are to be commended. Information like the Pony Express newsletter [on the web], just outstanding. I would like to see the ability for greater depth into research articles." (Jim Radz, Longwood)

In-kind Donations

Thanks go out to:
Malcolm Stuart of Orlando, who donated a liquid propane tank and regulator for use at the Thomas Farm fossil site. Malcolm is a teacher in the Orange County School system.
Jim Morris of Bainbridge, GA, who donated a set of rare, fossil horse tooth illustrations originally used in scientific publications of Dr. Chester Stock of the California Institute of Technology. Jim (see photo) is a Chief Deputy sheriff in Bainbridge GA and an avid collector of Miocene fossils in the Florida panhandle. He also was instrumental in helping Danny Bryant (see "Local Boy Makes Good") find important fossil localities that were used for Danny's Master's thesis.

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The 1996 Thomas Farm dig
The 5th Annual Thomas Farm fossil dig is scheduled for two weekends in the Spring of 1996. If you have participated before, or you are a newcomer, you are cordially invited to attend this relaxing, rustic, and educational retreat at a famous 20-million-year old fossil site located in rural northern Florida. Your returning of the enclosed form is a non-binding statement of intent so that we can plan for the two sessions. We will contact you in early 1996 so that you may exercise your option to participate and at that time send in a deposit to reserve your place on the dig. Each session is limited to 15 participants.

Session I. Thursday evening, April 18, to Sunday (mid-day), April 21, 1996
Session II. Thursday evening, April 25, to Sunday (mid-day), April 28, 1996

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Pony Express--Statement of Purpose:

The purpose of this newsletter is to communicate news and information and disseminate knowledge about fossil horses, particularly in Florida, and to develop a state-wide constituency that will support and enhance the research, exhibition, and educational programs offered at the FLMNH that pertain to fossil horses. Contributions to the Fossil Horse Fund are deposited into an account at the University of Florida Foundation, Inc., a tax-exempt entity, and will be used for the purposes stated here.

1st-time Readers:
You can receive future issues of the Pony Express with a one-time new-member fee of $20 made payable to the Fossil Horse Fund

Contributions and Support:
All supporters and other horse enthusiasts receive Pony Express and invitations to related activities that promote the research, exhibition, and education about Florida fossil horses.

Support Categories--1995

Editorial Staff:

Direct all Correspondence to:
New-member fee and other contributions should be made payable to:
Fossil Horse Fund and sent to the address listed above

Editor's email address: bmacfadd@flmnh.ufl.edu

Pony Express
Florida Fossil Horse Newsletter
Volume 4, Number 2
2nd Half 1995
ISSN# 1065-285X; Indexed in the Zoological Record

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