The New Student's Reference Work/Ungulates

Ungulates (ŭn′gū̇-lā̇ts), the name for an order of hoofed mammals. The larger proportion of mammals belong to this interesting order, which embraces the species useful to man, as the horse, ox, sheep, camel, pig and deer. They all walk, so to speak, on the tips of their toes, each toe at the end being incased in a horny hoof. They are naturally divided into two groups: the odd-toed and the even-toed mammals. The former includes the horses (q. v.) with a single hoof, the rhinoceroses with three toes on each foot and the tapirs with three toes on the hind feet and four (one of which is not used) on the fore feet. The odd-toed mammals (Perissodactyla) have had a long geological history, and many modifications can be traced through those found in the rocks. The horse, for example, sprang from ancestors with five toes, and between those remote ancestors and the modern horse with a single toe lie more than two and one half million years (see Evolution). The even-toed forms (Artiodactyla) include all those with cloven hoofs, as cattle, deer, sheep, goats, swine and the like. The hippopotamus has four toes on each foot. The swine has four toes, but the two outer are lifted above the ground and not of use in progression, and the cud-chewers have the toes reduced to two. These even-toed mammals likewise have a long history, and in the rocks are forms which lead up to those now existing.