Cervidae—Deer // Antilocapridae—Pronghorns // Bovidae—Bovids
Ruminants are artiodactyls that have the stomach divided into several chambers (commonly four), and food processing occurs in a series of operations, including regurgitation and chewing the partially processed plant material a second time ("chewing the cud"). By the time the food enters the small intestine, it has been thoroughly processed mechanically, chemically, and by bacterial biochemical action. This preprocessing before entry of the food into the primary absorption region breaks down many of the plant toxins that are a normal part of plant defenses, as well as synthesizing amino acids, vitamins, and other useful chemicals. Guthrie (1984) has hypothesized that this preprocessing as opposed to the later processing by microorganisms seen in the perissodactyls and proboscideans (the monogastrics) may be involved in the different extinction rates at the end of the Pleistocene.
The ruminants are highly successful and form the bulk of medium to large terrestrial herbivores. The pronghorns are (and were) an endemic North American group with considerable earlier diversity, but now survive as a single species (Antilocapra americana). The bovids are the most successful of the artiodactyls and include such forms as sheep, goats, antelope, bison, and muskoxen, among others. Distribution is primarily Holarctic, and several taxa successful in North America entered relatively late in geologic time; the bison and sheep are included in this group. The North American cervids of the Pleistocene are descendents of taxa that evolved in the Old World (Kurtén and Anderson 1980). Some, such as Cervus elaphus (the American "Elk"; European "Red Deer") and Rangifer tarandus (Caribou, Reindeer), are judged to belong to the same species in both the Old and the New World.
Ruminants lack upper incisors; instead, a firm pad of connective tissue allows a firm grip between lower incisors and the pad. A slight movement of the head is then sufficient to sever the plant material. In the lower jaw, the canine is incisiform, forming with the lower incisors a battery of eight incisor-like teeth. Cheekteeth are selenodont.
Guthrie 1984; Kurtén and Anderson 1980.
Last Update: 5 Dec 2008