UINATHERES

Uintatheres were rhino-like animals of Eocene age. The genus with the best fossil record is Uintatherium, a name derived from the Unitah tribe of indigenous native Americans that lived in the region now known as Utah. There is one known species: Uintathere anceps (Marsh, 1871) of early to middle Eocene age (56-38 million years ago) from the western United States. There are also a few species belonging to two other genera of uintatheres from this region.

Uintatherium anceps was 4 m (13’) long, 1.7 m (5.6’) high, weighed up to two tons, and had with robust legs with hooves. Uintatherium resembled a rhino, but the sternum of Uintathermum is quite different. Also the skull of Uintaterium is flat and concave, both of which are rare features not found in any other animal, except the extinct brontotheres.

Uintatherium anceps had a skull adorned with three pairs of bony protuberances. The posterior pair was the largest (up to 25-cm-long). The males had a pair of 15-cm-long sabre-like upper canines. Rhinos, giraffes, deer, and cattle have also have skull protuberances but lack sabre canines, except some antlerless deer, which have very large canines.

Genus Uintatherium is classified commonly as belonging to order Dinocerata, family Uintatheriidae, and subfamily Uintatheriinae. Genus Uintatherium was named by Leidy in 1872 for fossil material found in Bridger Basin near Fort Bridger, southwest Wyoming. Since that time, there have been discoveries of at least two other genera in the western United States. There have also been discoveries of closely related fossil material in Asia, namely in Mongolia, Kygyzstan, Kazakstan, and in the People’s Republic of China. The geologic age of these fossils is generally Eocene but might be late Paleocene in a few cases. Although the discoveries in Asia have been assigned to the same family as Uintatherium, some paleontologists place these Asian uintatheres in different subfamilies and in various genera (e.g. subfamily Gobiatheriinae/genus Gobiatherium). One of these species, G. inseperatus, is of middle to late Eocene age (48 to 34 mya) from Henan in east-central China (south of Beijing). More research is probably needed to sort out all the morphologic details as to how these Asian and western United States uintatheres differ.

The paleobiogeographic distribution of uintatheres is indicative of the presence of a former land bridge between North America and Asia. As I discussed recently in one of my previous blogs concerning Cenozoic land bridges, the Eocene land bridge between these two continents is known as “Beringia 1.” 

Useful Reference:

Wheeler, W.H. 1861. Revision of the unitatheres. Peabody Museum of Natural History Yale University, Bulletin 14, 93 pp., 14 pls.