Florida Fossil Horse Newsletter
Volume 7, Number 1 1st Half 1998
News From Powell Hall
- Shovel tusked gomphotheres
- Wooly Mammoths from the last Ice-Age
- Dwarf elephants that stood just 3 feet high (see photo below)
- Dima, the baby mammoth frozen in the Siberian permafrost for the last 44,000 years
- Modern Asian and African elephants
- Bruce J. MacFadden Program Director
- Erika H. Simons, Editor and Program Coordinator
- Contributor $20-99
- Friend $100-249
- Sustainer $250-499
- Patron $500-999
- Benefactor $1000+
- Rooney, James R., Queenstown, MD
- GTE Foundation, Matching contribution to education
- MacFadden, Bruce J., Gainesville
- Ahern, Brian, Temple Terrace
- Ahern, Tom, Temple Terrace
- Brevard Museum, Cocoa
- Bridell, Albert, M., Sanibel
- Budiansky, Stephen, Leesburg, VA
- The Jacobsons, Tampa
- McPherson, Brad, Shreveport, LA
- The Toomeys, Sanibel
- Ward, Pat & Larry, Orlando
- Watabe, Mahito, Okayama, Japan
- Bergman, Henry C., Tallahassee
- Bowen, Anne B., New Port Richey
- Brooks, Joseph C., Gainesville
- Carter, Audrey, Winter Garden
- Cassady, Tim, Bascom
- Churchill, Raymond G., Zephyrhills
- Dayhuff, Becky, Tellico Plains, TN
- Fite, Barbara, Lutz
- Flanigan, Valerie L., Naples
- Garson, Deborah, Brooklyn, NY
- The Hargraves, Gainesville
- Hickey, John H., Tampa
- Jones, Richard, Waterville, ME
- Lamb, Barbara J., Ainsworth, NE
- McMaster-Carr Supply Co., Elmhurst, IL (matching gift)
- Miller, Robyn, Jacksonville Beach
- The Millers, Frostproof
- The Moreys, Longwood
- Morris, Jim, Bainbridge, GA
- Nichols, D. Jeff, Fayetteville, AR
- Novak, Darlene, Gainesville
- Ott, Edgar A., Micanopy
- Preator, Phyllis, Cody, WY
- Quina, Charlotte, Lakeland
- Rowe, Paula, Bensenville, MD
- The Sinibaldis, St. Petersburg
- Skinner, Shirley M., Ainsworth, NE
- Watanabe, Osamu, Tokyo, Japan
- Wright, Marcia, Winter Park
FLMNH to Build a Western US Fossil Mammal Collection
An Unexpected Bonus
News From the Prep-Lab
The Enigmatic Rhinos from Thomas Farm
Carnivores from Thomas Farm
The Elephants Are Coming!
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News from Powell Hall
Central Gallery at Powell Hall (Photo by Stan Blomeley)
Our new FLMNH exhibits and education center at Powell Hall opened to the public on 30 January 1998. During the first month of operation, almost 14,000 people visited the museum. Several new and exciting displays are available, with more planned for the next four years. Currently we have two fossil horse skeletons on exhibit in our Central Gallery: an 18 million-year-old Parahippus from Thomas Farm and a 1.5 million-year-old Equus from Leisey Shell Pit in Hillsborough County. We also are planning to have a skeleton of Thomas Farm Archaeohippus placed on exhibit this Spring. We hope that you all will have an opportunity to come and visit Powell Hall.
We have initiated several new programs at Powell Hall. One that we are very excited about is the Frequent Visitors Club. Visitors register (at no charge) to become members of the Frequent Visitors Club and each time they visit Powell Hall they are allowed to select a natural history object that they may take home with them (for keeps). The objects to choose from include a fossil shark's tooth, modern shell, fossil clam, squash seed, armadillo scute, and fossil plant. With almost 2,000 members signed up during the first month that Powell Hall
Bruce J. MacFadden
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FLMNH to Build a Western US Fossil Mammal Collection
The FLMNH has one of the largest fossil vertebrate research collections in North America. Consistent with our mission as the state museum, more than 90% of these collections are from Florida localities. Nevertheless, as we diversify our research and public outreach programs, it is time for us to develop collections from other regions as they pertain to current initiatives in our museum.
In June the Pony Express will sponsor its first western trip to visit museums and dig Oligocene fossils in western Nebraska. My preliminary visit to this region last summer indicated that this trip will have lots of attractions and excellent potential to find fossils. Accordingly, one of our goals for this new program will be for us to make precisely documented collections for the FLMNH from classic Oligocene exposures in this region of the west. These new collections are sure to include extinct mammals such as oreodonts, rhinoceroses, rodents, early lagomorphs (related to modern rabbits and their kin), camels, carnivores, and of course, fossil horses. With regard to the latter, the classic Oligocene western localities contain two genera of horses, Mesohippus and Miohippus. Interestingly, these same two genera of horses are the earliest known from Florida, about 28 million years old. Fragments identified as Mesohippus are known from the "I-75" locality uncovered during the late 1960s from just SW of Gainesville when the Interstate 75 was being built., On the other hand, Miohippus is known from a few fragments in our collection, but by far the most spectacular specimen of this horse is the individual collected from St. Petersburg and donated to the FLMNH by the Tampa Bay Fossil Club in 1995 (see Pony Express, vol. 4, no. 2, 2nd Half 1995).
After the scanty record during the early Miocene described above, extensive collections of Florida fossil horses come from the middle Miocene 18 million year old Thomas Farm locality. By this time the horses have evolved to include three genera, including the common three-toed Parahippus, the tiny Archaeohippus, and the very rare browsing Anchitherium. The specimens of Oligocene Mesohippus and Miohippus in our collections (whether they are from Florida and Nebraska) are about 10 million years older than the horses from Thomas Farm. With new Oligocene collections we therefore will have an enhanced understanding of the ancestry of fossil horses. For example, a horse skeleton collected by Tom and Brian Ahern last year from Nebraska has been prepared and is providing clues to the differences between Mesohippus and Miohippus (see Pony Express, vol. 6, no. 2, page 5 article by Jay O'Sullivan below). The addition of Oligocene collections will allow FLMNH and museum scientists, students, and visiting researchers to make comparisons of the characters that have changed through time documented by 28 million years of evolution, from the Oligocene until horses became extinct in Florida about 10,000 years ago.
Fossils acquired during the western field trips will also provide a broader diversity of possible
specimens to be placed on exhibit. We are very excited about a spectacular fossil Oligocene titanothere
("thunder-beast," an extinct family whose modern relatives include tapirs, horses, and rhinos) collected
from this region that will be loaned to us by Steve and Suzan Hutchens for display in our new museum
building at Powell Hall.
Bruce J. MacFadden
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An Unexpected Bonus
Watching the preparation of the donated Oligocene horse fossil filled me with the same sort of anticipation a child feels on Christmas morning. I could hardly wait to get my hands on it! But, wait I did. As the rock-hard wrapping came off, I grew to suspect that this gift was a more valuable addition to the museum's collection than had been expected originally.
Little horses such as this one that are recovered from the Early Oligocene of Nebraska usually are assigned to the genus Mesohippus. However, the slightly larger and more advanced horse Miohippus is also present in Oligocene sediments of Nebraska. The species Miohippus obliquidens is fairly abundant in the area. As the rock matrix was painstakingly removed from the fossil, I began to suspect that I was looking at a specimen of Miohippus, not Mesohippus.
The first clue was the length of the face and condition of the preorbital fossa (pit) of this specimen. Generations of paleontologists have sought an easy way to tell Miohippus from Mesohippus, with little success. They found that Miohippus is typically somewhat larger and looks slightly more like later horses than does Mesohippus. In particular, Miohippus has a longer face. The depression known as the preorbital fossa has a distinct indentation in front of the eye orbit, and tapers to a shallow groove towards the middle of the snout. Mesohippus has the shallow depression, but lacks the pinched look in front of the eyes. The donated horse specimen from Nebraska has the long face and pinched fossa of a Miohippus.
Although I had seen illustrations of complete skulls of Miohippus, there are only a few specimens of Mesohippus and no Miohippus in the collection of the FLMNH. Since my doctoral research on the Miocene dwarf horse Archaeohippus requires me to figure out to which species of Miohippus it is most closely related, it is very important that I learn to recognize Miohippus. The prospect that we now had a relatively complete specimen of Miohippus here at the museum was exciting, and warranted further investigation.
The most recent study of these horses offers only one (supposedly) unambiguous distinguishing character for Miohippus. The third metatarsal (toebone) has a small smooth facet (area) for articulation with the cuboid bone in the ankle. Evolutionarily, this is due to the broadening of the third metatarsal, as it becomes the primary (and eventually only) weight-bearing metatarsal (cannon bone). According to most authors, this articular facet is not found in Mesohippus. It is as prominent in the new specimen as it is in Archaeohippus and Parahippus. Unfortunately, every specimen I found in our collection labeled Mesohippus also appears to possess this cuboid-MTIII articular facet, though to a lesser degree. Now, this could be the result of mislabeling; as I said above, nearly everything that comes out of the Oligocene of the western United States is assumed to be Mesohippus. Or, it could be that the facet is weakly present in some specimens of Mesohippus. Unsatisfied, I sought more solid characters to differentiate these two very similar horse genera. I think I may have found some.
The lengthening of the horse face over evolutionary history includes the migration of the orbit (socket) of the eye further back on the skull. This can be measured by observing the location of the front border of the orbit in relation to the tooth row. In Mesohippus, the forward edge of the orbit can be even with the back half of the first upper molar (M1). In Miohippus, the orbit is even with the back half of the M2. (In Equus, the orbit has withdrawn to a position over the M3.) I had noted this condition only from photographs. Now, with the donated specimen, I can confirm that this is not the result of post-depositional deformation of the fossil. Looking at the underside of the skull, I noticed that the zygomatic arch (the cheekbone) is set back in Miohippus. The opening through which the cheek muscles pass extends to a point next to the M3 in Mesohippus, but is behind the tooth row in Miohippus. This arrangement of the teeth in relation to the jaw muscles affects the mechanics of chewing, and might indicate dietary differentiation between Mesohippus and Miohippus.
Using the location of the eye and cheekbone, I was able to go to our
small collection of Oligocene horses from the western United States and identify
some skull fragments to genus. Several specimens that are labeled Mesohippus
look like Miohippus to me. Without the addition of this wonderfully intact skull with
its associated postcranials, this would not have been possible. In a couple of months,
I will visit the American Museum of Natural History in New York to look at the collection
of Oligocene and Miocene horses there. Thanks to the generous donation of this
specimen of Miohippus, I feel that I will have a better understanding of this genus
and its contemporary, Mesohippus.
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News from the Prep Lab
(Photo by Erika H. Simons)
Being from Florida, I'm used to the sands, clays and creek beds found here. However, last year, a fossil horse from Nebraska was donated to the FLMNH (see page 3, this issue). It was encased in a fifty pound block of HARD clay held in a plaster jacket; much of it fractured into several big pieces. The jacket was made to include some extraneous rock on the underside for protection. This was removed the old-fashioned way, with a hammer and chisel. With such hard clay it is good to use fractures to your advantage, just be aware that often times fossils provide those cleavage points where the fractures occur. This can end in either perfect cleaving of the rock from the fossil, or regrettably a break, although clean, in the fossil itself. Little bone was in the extraneous rock, but once fossils began to appear, the block was prepared in detail in the lab.
The most valuable tool has been a pinvise for detail work; of course, an awl would suffice (dental picks used on softer matrices just wear down). A hydraulic Airscribe is invaluable, as it allows for detail work with lots of rock removal. The drawbacks of an Airscribe are threefold: the intense and loud buzzing makes it difficult to work for extended periods of time, the vibrations can cause brittle bones to crumble, and the dust produced. The dust isn't just messy, but it also contains silica, which is really NOT good to breathe, especially for extended periods, so WEAR A RESPIRATOR! If anything, at least get some of the disposable ones from a hardware store. As for glues, butvar is a good all-purpose hardener when thinned with acetone and a good glue for some of the more stable joints. Butvar can be dissolved with acetone, and hardener can be peeled off. Once bone is exposed, I clean and harden it. If later I want to get it cleaner, I just peel off the hardener and harden again. Cyanoacrylate glues are very useful, especially with the more brittle scapula and vertebrae. Vertebrae especially are difficult because the matrix fills the neural canal and surrounds all the protruding processes. If the rock fractures, so does the little process or fragile arch.
This was my first time working with such a hard matrix, so all I can say is, when in doubt,
rely on the pinvise. It may not save time, but it does save fossils. Patience and time are great
assets for this kind of preparation.
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The Enigmatic Thomas Farm Rhinos
Although abundant throughout the late Miocene into the early Pliocene in Florida, rhinos are rare in earlier times. With the exception of a few isolated specimens, the Thomas Farm fossil locality contains the best early record of rhinos in Florida. Remains of two rhino species, Menoceras barbouri and Floridaceras whitei, are found in the compact Thomas Farm clays and sands, but they are elusive in both fossil abundance and in what we know about them. Horace E. Wood described both species in 1964 from a collection of Thomas Farm fossils at Harvard University. (See: Wood, Horace E. 1964. Rhinoceroces from the Thomas Farm Miocene of Florida. Bulletin of the Museum of Comparative Zoology, Vol. 130, pp. 363-386.)
Menoceras barbouri was the older of the two species. Menoceras was a member of an extinct lineage of rhinos that is characterized by a unique set of double nasal horns. Living African rhinos have two horns, a large horn in front and a smaller one behind, but Menoceras had two equally sized horns positioned side by side. Unfortunately, the horns of extinct rhinos are not made of bone and do not preserve in the fossil record. Instead, they are made of keratin, much like your fingernail or the hoof of a horse, and grow throughout life. We can make some observations about the horns of extinct rhinos by the rugosities on their nasal bones. Rugosities are roughened areas where the horn attaches to the skull. hile no complete skull of Menoceras has ever been found at Thomas Farm, specimens from other fossil localities demonstrate that the females were hornless and only the males possessed these double horns. You can imagine that the males may have utilized these horns in a battering ram-like fashion, fighting other males for mates, or in territorial disputes. By rhino standards, Menoceras was small. It weighed much less than any of the living rhinos, was more slender and a quick and agile runner. The genus Menoceras migrated from Eurasia during the latest Oligocene time. The only other rhino living in North America at the time of this migration was another two horned rhinos named Diceratherium. Diceratherium never lived in Florida and was extinct by the very early Miocene, perhaps due to competition with Menoceras. As a result, Menoceras may have been the first rhinoceros to ever wander into Florida.
The second Thomas Farm rhino, Floridaceras whitei, was much larger, about the size of a modern black rhino. It was a true gargantuan for its time and it easily dwarfed the contemporary Menoceras and other North American rhinos that lived before it. Floridaceras belongs to a group of large hornless rhinos, known as the aceratheres (beasts without horns), that migrated to this continent during the earliest Miocene. While they lacked nasal horns, aceratheres retain a pair of tusk-like lower incisors that may have been used as defensive weapons. Three different genera of aceratheres lived in North America during the Miocene: Paraceras, Aphelops and Floridaceras. Paraceras is well known outside of Florida and Aphelops is very common throughout the late Miocene in Florida. Floridaceras was an early Miocene form and is the rarest of the three. In fact, Thomas Farm contains the only known record of this elusive rhino. With very few skeletal remains it is difficult to say much about it. Its skull and dentition are more primitive than the later aceratheres and Floridaceras probably browsed on soft forest leaves. Despite its great weight, Floridaceras had relatively long legs and was more slender than living rhinos. Floridaceras appears to have been able to achieve surprising speed when running. While most rhinos have three toes per foot, Floridaceras had four toes on its front feet. The loss of the most lateral digit occurs early in rhino evolution but for some reason, Floridaceras retained this primitive characteristic. Perhaps the extra digit aided Floridaceras in supporting its great weight and prevented it from sinking when running in mucky, swampy conditions.
Floridaceras and Menoceras died out before the late Miocene.
They were probably adapted to eating soft forest vegetation.
As the Miocene progressed, the North American climate became more arid.
Grasses and other tough plants spread across the continent and Menoceras
may have been outcompeted by horses that had evolved to eating these plants.
Likewise, Floridaceras was replaced by two other rhinos with more advanced
dentition. One of these was its close relative, Aphelops, and the other was
a short, squat rhino known as Teleoceras. Both of these died out about
5 million years ago and were the last rhinos to roam North America.
Matthew C. Mihlbachler
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The Carnivores of Thomas Farm
The Thomas Farm carnivores present an interesting snapshot of early Miocene times and early, modern carnivore evolution. As in most fossil assemblages, the carnivore material is relatively scarce, however, four families and nine genera of predators have been identified including five new, two western immigrant and two archaic species. The early Miocene represents an important transition from the late Oligocene primitive carnivores to the Miocene more advanced carnivores.
Three mustelids (weasels, skunks & relatives) have been found at Thomas Farm. Oligobunis floridanus is a remnant carnivore considered part of the stem mustelid radiation during the Oligocene and went extinct during the early Miocene. It is the largest mustelid at the site and is characterized by rather large lower fourth premolars and first molars. It is thought Oligobunis may have been a badger/wolverine-like animal that filled the scavenger niche, eating bones and carcasses. Miomustela sp. and Leptarctus ancipidens are part of the modern mustelid radiation, which also started in the late Oligocene. Miomustela is the smallest carnivore found at Thomas Farm and is represented by only a few fragmentary remains. Leptarctus is a relatively common western species and is approximately the same size as the modern weasels.
The dog family (Canidae) is represented by the largest number of fossil carnivore specimens from Thomas Farm. Canid evolution is highlighted by an early Miocene split of the primitive Hesperocyoninae into the two major groups of canids that lived during the later Tertiary. Osbornodon iamonensis (formerly Cynodesmus) is a basal ancestor of the modern dogs, subfamily Caninae, and most abundant predator of Thomas Farm. It was the largest canids and most gracile of the Thomas Farm predators. Tomarctus canavus is one of the earliest known members of the Borophaginae, a group of canids that evolved several different forms including the hyaena-like Osteoborus. The borophagine went extinct in the late Pliocene. Tomarctus is characterized by shorter, more robust limbs and shorter face than Osbornodon. Euplocyon spissidens was a small, rare canid and is characterized by having an extra cusp extending along the shearing length of the molar. This structure implies a more carnivorous lifestyle than its other canid counterparts.
Two bear-dogs, Amphicyon longiramus and Cynelos caroniavorus, are found at Thomas Farm. The Amphicyonidae is considered the most primitive of the "modern" carnivore families. They retained a full dentition including the upper third molar, which was lost in all other families. Bear-dogs did not survive beyond the Miocene in North America. Amphicyon is the largest and third most abundant predator at Thomas Farm. Cynelos is a smaller bear-dog and is only known from a few specimens. The primitive ursid (bear family) Phoberocyon (formerly Hemicyon) johnhenryi is of approximately equal size to Amphicyon but has more slender limbs. Phoberocyon evolved dental and locomotor adaptations equivalent to canids. This bear is known from only a few dental specimens and several post-cranial bones from Thomas Farm.
The two major dogs and Amphicyon represent most of the
Thomas Farm carnivores, while the remaining are known
form only a few specimens. There were at least 12 genera of
ungulates and three species of rodents present as potential food,
of which the horses Parahippus and Archaeohippus were probably the main prey.
The carnivores from Thomas Farm are unusual because they existed during
"the cat gap", a period in which "cats" (felids and nimravids) were absent from
the North American fossil record. Cat-like predators disappeared at the end of
the Oligocene and did not reappear for eight million years. The lack of these
meat-specialist carnivores probably had a major influence on the evolution of
the new genera present a Thomas Farm. The Thomas Farm carnivores represent
very general forms, which were neither as fleet runners nor as highly adapted to
eating meat compared to previous and subsequent specialized predators.
The mixture of ancestral and experimental predator forms portrays a transitional,
quickly evolving stock of predators. Although the animals are fairly generalized
in anatomical adaptations, they do show obvious differentiating features, which
fill the predatory, scavenging, and omnivorous roles within the ancient
Thomas Farm ecosystem.
Casey M. Holliday
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THE ELEPHANTS ARE COMING! THE ELEPHANTS ARE COMING!
In this informative and educational exhibit, mounted skeletons of modern elephants and their ancestors along with fossils and interactive exhibits will explore the evolution, ancestry, and relatives of the proboscideans, those unique mammals we call elephants. This amazing group of animals gets its name from its most defining and unusual feature - its trunk or proboscis in fact, the word "proboscidean" means "trunk bearer".
With the exception of Antarctica and Australia, fossil proboscideans have been found on every continent. The earliest ancestors of modern elephants appeared more than 50 million years ago in the early Eocene Epoch and had not yet developed recognizable trunks. They may have been similar in appearance to the "coney" or hyrax, a small tailless, short-nosed herbivore found in Africa and the Middle East.
Near the end of the Oligocene Epoch, about 30 million years ago, proboscideans possessing both trunks and tusks are found. In another six million years, early in the Miocene Epoch, Gomphotherium, an ancestor to modern elephants, appears. The exhibit ELEPHANTS! features a rare and nearly complete skeleton of a shovel tusked gomphothere found in Nebraska in 1993.
Mammoths, although now extinct since the end of the last Ice Age, 10,000 years ago, are the closest relatives to modern elephants. The exhibit ELEPHANTS! brings the mounted Hebior Mammoth to the Florida Museum of Natural History. Discovered in 1994 in Wisconsin, this woolly mammoth, standing 13 feet high is the largest and most complete ever found.
Dwarfing in elephants is seen more than once in the fossil record. In the exhibit ELEPHANTS! you can see one of the smallest known elephants, a mounted specimen from Sicily that stands no more than three feet high. Dwarf mammoths are also known from the Catalina Islands off the coast of California, and Wrangel Island in the Siberian straits where a dwarf mammoth is reported to have existed until about 3000 B.C.
While most of the fossils accompanying the ELEPHANTS! exhibit are skeletons, this exhibit has a body cast of Dima, the baby mammoth which was found frozen in the permafrost of Siberia. It is all the more remarkable for having preserved, not only the skeleton, but skin, stomach contents, and internal organs as well, to give us a rare glimpse into the past.
ELEPHANTS! also presents a mounted skeleton of a modern Asian elephant. Similarities and differences between modern elephants and fossil relatives are readily evident when all the mounted skeletons are viewed.
Modern mammals, such as manatees and hyraxes, although seemingly
quite different animals are nevertheless, close cousins of the elephants.
ELEPHANTS! explores these relationships and much more as it takes
us on a fascinating tour of proboscidean evolution, natural history, and folklore.
This educational journey is presented through the media of actual fossils,
photographs, video presentations, and text, as well as interactive
walk-throughs and hands-on exhibits.
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Pony ExpressFlorida Fossil Horse Newsletter
Volume 7, Number 1
ISSN# 1065-285X; Indexed in the Zoological Record
Direct all Correspondence to:Pony Express
Exhibits & Public Programs
Florida Museum of Natural History
Powell Hall -- P.O. Box 112710
Gainesville, FL 32611-2710
Phone: (352) 846-2000 extention 204
You can receive future issues of the Pony Express with a one-time new-member fee of $20 made payable to the UF Foundation
Contributions and Support: All supporters receive Pony Express and invitations to related activities that promote the research, exhibition, and education about Florida fossil horses.
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should be made payable to:
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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.
Donations to the Fossil Horse Fund -- 1997 - 1998
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