Pe·ris·so·dac·ty·la (pai’ris-oh dak ti’lah)
From Greek perissos, strange, of numbers odd; daktulos, a finger or toe.
Orden Perissodactyla – First described in 1848 by Anatomist Sir Richard Owen (1804-1892)
Odd-toed” or “odd-hoofed”mammals make up the Perissodactyla. Like the “even-toed”Artiodactyla, perissodactyls are unguligrades; that is, they walk on the terminal bones of the toes and have enlarged toenails forming hoofs. Unlike artiodactyls, perissodactyls have a mesaxonic foot structure (the symmetry of the foot passes through the third digit, bearing the animal’s weight)
Rhinos, tapirs, many extinct horses, and other extinct groups walk on three toes, whilst in recent horses the mesaxonic foot have evolved so that the non-weight bearing digits have atrophied away, while the third toe has enlarged, so that modern equines have only one toe.
Perissodactyls have a mesaxonic foot and a unique ankle joint, where two of the ankle bones (the astragalus and the navicular) are articulated via a saddle-shaped joint.
The extant perissodactyls are a diverse group, with no generalized appearance. At one extreme you find lithe and graceful horses; on another, huge, tank-like rhinoceroses; and in between, the vaguely pig-like tapirs.
Perissodactyls have a simple stomach, in contrast to the chambered structure of most artiodactyls. Their cecum is enlarged and sacculate, and in it some bacterial digestion of cellulose takes place.
The link below takes you to the Abstract:
Nutritional Basis for Food Selection by Ungulates. (1982) THOMAS A. HANLEY
Adaptations of digestive systems in non-ruminant herbivores (1988) DAVID J . CHIVERS
