(cohort Ferungulata, superorder Paraxonia)
The even-toed ungulates, an order of mammals that includes the camels, pigs, and ruminants, together with numerous extinct varieties. They are the most successful of the hoofed animals. They are descended from the Condylarthra, and underwent a spectacular burst of adaptive radiation in Eocene and early Oligocene times. They are terrestrial or amphibious herbivorous mammals. Except for the camels the gait is unguligrade. The axis of the foot is paraxonic; the first digit is absent, the second and fifth often reduced or lost. The digits terminate in hoofs, the third and fourth of equal size, usually flattened on the inner and ventral surfaces. The dentition is specialized; the upper incisors are lost in some species, the lower incisors biting against the hardened gum of the premaxilla; the canines may form tusks; the premolars are not molarized (i.e. adapted for grinding, as in many Perissodactyla), elongated hypsodont molars providing grinding surfaces, the four cusps often being developed into longitudinal ridges. The tongue is large, mobile, protrusible, pointed, and the papillae are often horny. The stomach is elaborate. The brain is moderately well developed in later forms, although the cerebral hemispheres only partly cover the cerebellum, and in early and some modern forms (e.g. hippopotamus and pig) the brain is small. The olfactory sense is important. Visual, auditory, olfactory, and tactile signals are important in communication.
Subjects: Zoology and Animal Sciences.