Order Artiodactyla


There are four living families of ruminants, so-called because of the complex food-processing system. Plant material is taken into the multi-chambered stomach and stored in the rumen. Later, the food is regurgitated, rechewed (chewing the cud), and reswallowed, eventually passing from the rumen through the reticulum, omasum, and abomasum (all parts of the stomach) and into the small intestine. In these chambers, microorganisms process the plant material, breaking down cell walls and allowing digestible material to be attacked. The process is highly efficient, allowing less bulk and more selectivity than among the perissodactyls where microorganisms do not get a shot at the ingested material until after it leaves the stomach.

McKenna and Bell (1997) subdivide the ruminants into three superfamilies (Cervoidea, Giraffoidea, and Bovoidea). Within our region, the Cervoidea contains the Antilocapridae (pronghorns) and the Cervidae (deer).

Cervoidea: Pronghorn and Deer


The Antilocapridae sometimes are placed in the Bovidae, but McKenna and Bell don't even put them in the same superfamily. Pronghorns are represented by only one living species, Antilocapra americana, the Pronghorn. Often called antelope in the USA, this is inappropriate since none of the species of antelope occur in the New World; slightly better, though seldom used, is Pronghorn Antelope. Although only the Pronghorn survives, a number of genera are known from the later Tertiary and the Quaternary. Pronghorns occur throughout the Great Plains and through the desert Southwest and northern Mexico. Although the hypsodont teeth would suggest they are primarily grazers, they rely heavily on browsing. Pronghorns are the fastest terrestrial North American mammals and have extraordinary physiological adaptations for efficient oxygen utilization. Both sexes have horns, and the taxon is the only artiodactyl whose horns are shed periodically (a new sheath grows beneath the old, forcing it off; the bony horn core is not shed). This also is the only artiodactyl with a branched horn.

Smithsonian Field Guide: Antilocapridae.


Deer are characterized by the possession of antlers, bony projections of the frontal bones that are shed periodically. Although often these are called horns in common parlance, horns consist of horn (a keratinous structure) over a bony horn core. This is quite different from an antler which has a dermal covering (the velvet) during antler growth that is shed when the antler reaches maturity. Thereafter, the antler consists of naked bone. In most species, only the male possesses these (caribou is an exception, with both sexes having them). As in the other ruminants, there are no upper incisors and the lower canines are incisiform, so that it appears that they have four lower incisors on each side. Cheek teeth are brachyodont.

The local El Paso cervid is the Mule Deer (Odocoileus hemionus), with a small population in the Franklin Mountains and with populations spread widely throughout the region. In the eastern portion of the region, and in the southwest, the White-tailed Deer (O. virginianus) occurs. Where the two occur in the same area (as in southwestern New Mexico), the White-tailed Deer tends to be in the montane and riparian situations and the Mule Deer in more open or arid country.

Also native to the region is Cervus elaphus, the Wapiti ("Elk"—the common names tend to be confusing, because the Elk of the Old World is the Moose of the New World, and the "Elk" of the New World is the Red Deer of the Old). The original populations (described as Cervus merriami) of the Southwest were eliminated by over-hunting, and present populations have been introduced from elsewhere. Long known as C. canadensis, the animal is another example of conspecificity with the Old World form and a late-comer to the continent.

Smithsonian Field Guide: Cervidae.

Giraffoidea: Giraffes and Okapis

The Giraffoidea consists of a single living family, the Giraffidae, whose members include the Giraffe and the Okapis. These are limited to Africa. Hornlike structures are present in both sexes of giraffes and in male Okapis—the structures are unique in consisting of a bony core covered by hair-covered skin. The bony core (ossicone) forms as cartilage, separate from the skull bones, that ossifies and eventually fuses to the skull bones; it continues growth throughout life (in the Giraffe, there are paired horns over the anterior part of the parietal with eventually the anterior base growing over the parietal-frontal suture; there is a third, medial horn that develops over the front part of the frontals and the rear of the nasals).

Bovoidea: Bovids

The Bovoidea includes only the family Bovidae. However, this is an extremely large and successful family (about 44 genera and 111 species), including such taxa as cattle, bison, goats, sheep, antelopes, and mountain goats. The true antelopes (Antelopinae) are native to the Old World, with only the Saiga making it briefly into the New World in Alaska during the Pleistocene. Locally, Oryx (Oryx gazella) have been introduced into the White Sands area and have adapted well (perhaps too well).

Caprinae: Sheep and Goats

The Caprinae includes the sheep and goats. The Bighorn Sheep (Ovis canadensis) is native to our region, with surviving Desert Bighorn in the San Andres and the Big Hatchet mountains. Almost eradicated from the Southwest, they now are protected and populations being reestablished by introduction (including into the Big Bend area). It was a late Pleistocene arrival in the Southwest, and other caprines (and late-arriving bovids in general) in North America are northern animals. These include the Musk Ox (Ovisbos moschatus), Dall Sheep (Ovis dalli), and Mountain Goat (Oreamnos americanus). The latter, however, had a late Pleistocene representative (O. harringtoni) into the Southwest. Barbary Sheep (Ammotragus lervia) has been introduced into northern New Mexico, and Ibex (presumably Capra aegagrus) into the Florida Mountains near Deming, NM. The domestic sheep and goats (Ovis aries and Capra hircus) are Old World taxa.

Bovinae: Bison and Cattle

Bison arrived in the New World from the Old during the Pleistocene, and there were several now-extinct species. The bison are closely related to cattle, and many modern mammalogists seem to be considering them as congeneric, in the genus Bos. Most paleontologists, such as myself, tend to preserve the genus Bison as a matter of convenience, clearly separating Bison from Cattle. The surviving North American species is Bison bison (the European species is B bonasus) and occurred in the millions on the Great Plains when first encountered by Europeans. During the Holocene, our area appears to have been marginal to Bison populations, with the main populations to the east of the eastern mountain ranges; however, small populations may have moved through the area (there are archaeological and paleontological remains in southwestern New Mexico).

Cattle, of course, are introduced from the Old World. Most are Bos taurus, but cattle from the subcontinent of India are Bos indicus. Many Southwestern cattle are various degrees of hybrids between the two (the Indian form being more adapted to heat). Cattle and Bison can be most easily told apart by the horns (or horn cores): in cattle (of our breeds), the horns curve out and anteriorly, whereas in Bison, they curve out and posteriorly. Less usefully, the nasal extension of the premaxilla contacts (or nearly so) the nasals in cattle, but not in Bison. Post-cranial elements are difficult to discriminate.

Smithsonian Field Guide: Bovidae.


Last Update: 27 Jan 2008