Order Perissodactyla


The extant perissodactyls include the various species of horses (Equidae, Equus), the rhinoceroses, and the tapirs. Although all have a strong fossil presence in North America (and horses had most of their evolution in North America), only the tapirs survive in the New World. The rhinos disappeared by about the end of the Pliocene, but horses were common until about the end of the Pleistocene.

In our region, most large fossil faunas have three species of Equus represented, with sometimes a fourth. All were gone by early Holocene times, as were other species of horses in the New World, including those of South America.

The modern domestic horses (Horse, Burro) are introductions from the Old World. The Horse (Equus caballus) is feral in a number of places in our region, and the poor condition of them on White Sands Missile Range a few years ago hit the papers frequently. The Burro (Donkey, Ass: Equus asinus) likewise has a number of feral population in the region. Horses are highly cursorial, with only one toe per foot. The single weight-bearing metapodial (metapodial III) often is called a cannonbone (as are the fused third and fourth metapodials of camels and ruminants).The teeth of Equus are unmistakable; examples of uppers and lowers are shown in menu item "Dentition 2".

Tapirs (Tapirus) survived into the late Pleistocene locally, but now are (in the New World—the Old World has one species in Southeast Asia) limited to southern Mexico south into South America as far as Paraguay. Three species are extant in the Western Hemisphere.


Last Update: 26 Jan 2008

Centennial Museum and Department of Biological Sciences, The University of Texas at El Paso