Ungulates are animals with hooves. Creatures such as bison and deer are the even-toed ungulates, because they have either two or four functional toes per foot. Technically, these form the taxonomic order Artiodactyla as opposed to the Perissodactyla—horses, rhinoceroses, and tapirs—who have an odd number of toes.
Both groups were well represented in North America until extinctions at
the end of the ice age. Deer belong to the family Cervidae and are characterized by
having antlers—bony projections of the skull that are shed annually. Bison and
relatives belong to the Bovidae, characterized by having horns—tough, never-shed
coverings over bony projections of the skull. The Pronghorns (often miscalled antelope)
belong to a family—the Antilocapridae—differing from the bison family in that the horn
is shed. A new horn grows beneath the old and pushes it off. The horn also is unique in
being branched. Only these three families of ungulates survived the mass extinction of
some 11,000 years ago. The native camels, horses, and tapirs have disappeared into the
mists of the past.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.