Taxonomic Description of the White Springs Oreodont

Oreodonts, an extinct group of extinct hoofed mammals most closely related to sheep, were very common in the western United States 35 to 20 million years ago (late Eocene through early Miocene). Some of the first fossils collected out west during the 1850's were oreodonts. Around the Big Badlands of South Dakota and adjacent Nebraska, extensive "oreodon" beds are replete with these mammals. Oreodon fossils are conserved and exhibited in many U. S. natural history museums. Consisting of an overall diversity of about 50 species, oreodonts were mostly small dog- to large pig-sized herbivores, feeding predominantly on leafy vegetation.

Despite the fact that oreodonts were very common out west, they are exceedingly rare in Florida. Prior to 1990, our entire knowledge of Florida oreodonts was known from only a handful of teeth and bone fragments from a few sites. Then, an extraordinary locality was discovered along a river in N Florida that has since yielded a fantastic collection of fossilized skulls, jaws, and limb bones. This underwater locality is still under excavation by FLMNH scientists. Ironically, it is one of the earliest known terrestrial sites in Florida, when it was first emerging as an island, 30 million years ago. This new collection of Florida oreodonts is currently under study by Bruce J. MacFadden, FLMNH curator and Gary S. Morgan, vertebrate paleontology curator at the New Mexico Museum of Natural History.

After comparison with other oreodonts from all around the U. S. in the American Museum of Natural History collections, MacFadden and Morgan have determined that this Florida oreodont represents a new species of Mesoreodon that lived about 25 million years ago. The genus Mesoreodon is otherwise best known from 25-million-year-old localities in South Dakota and Nebraska. It lived alongside a few different species of camels, horses, rodents, and bats, all natives to ancient Florida, as well as marine mammals closely related to modern-day sea cows.

Taken together, the various bones, skulls, and jaws of Florida Mesoreodon were sufficient to reconstruct a "composite" (i.e., taken from several individuals) skeleton for exhibition in the Hall of Fossil Hall at the FLMNH. It is currently on display in the FLMNH Skeletons temporary exhibit. Late Oligocene-early Miocene land mammal fossils are rare in Florida, so Mesoreodon will be a focal-point for our transition from the late Oligocene to early Miocene time.

Bibliography

Non-technical

Benton, M. J. 1991. The Rise of Mammals. Crescent Books, New York.

Osborn, H. F. O. 1910. The Age of Mammals. Macmillan. New York.

Savage, R.J. G and M. Long. 1986.. Facts On File Publications, New York.

Technical

MacFadden, B. J. 1980. An early Miocene land mammal (Oreodonta) from a marine limestone in northern Florida. Journal of Paleontology 54:93-101.

Schultz, C. B. and C. H. Falkenbach. 1968. Phylogeny of oreodonts. Bulletin of the American Museum of Natural History 139:1-498.

Simpson, G. G. 1945. The principles of classification and a classification of mammals. Bulletin of the American Museum of Natural History 85:1-350.

Stevens, M. K. and J. B. Stevens. 1996. Merycoidodontidae and Miniochoeridae, p. 498-580. In D. R. Prothero and R. J. Emry (eds.), The Terrestrial Eocene-Oligocene Transition in North America. Cambridge University Press, New York.