Vertebrate Zoology: A Study Guide - T. A. Dauda 2014

Metazoa
Infraclass Eutheria, or placental mammals
Order Perissodactyla

The order Perissodactyla comprises predominantly large animals of rather diverse body Structure (Fig. 67), typically featuring a well-developed third digit which forms the axis of the limb. This digit is encased in a rounded horny sheath (the hoof), while the remaining digits are less developed or vestigial. The limbs move in a single plane, and collarbones are absent. These animals are capable of rapid locomotion.

At present, only 15–16 species of perissodactyls survive, among which horses are the best known. This group includes Przewalski's horse, zebras, kulans, and donkeys. They possess a well-developed third digit, whereas the second and fourth digits are reduced to small bones hidden beneath the Skin. The tail is long and more or less hairy. These animals lead a gregarious lifestyle, grazing in open expanses where they feed on coarse plant matter. Their offspring are born precocial, capable of following the mother shortly after birth.

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Fig. 67 Perissodactyl mammals:

1 — Malayan tapir; 2 — Indian rhinoceros; 3 — zebra.

Today, Przewalski's horse is no longer found in the wild. Small groups are maintained across various zoos, with the total population not exceeding 200 individuals. Przewalski's horse served as the ancestor of various domestic horse breeds.

Relatively small equids still occur in the wild, such as the kulan, which inhabits southern Turkmenistan and certain other parts of Asia. In our country, this species is protected by law. Zebras are widely distributed across the African savannas.

Another well-known group of perissodactyls is the rhinoceroses, which have three-toed forelimbs and hindlimbs. They bear one or two horns on their frontal and nasal bones, while canines are absent. Africa is home to the white rhinoceros, whereas South Asia harbours the Indian rhinoceros. The latter is the largest land mammal after the elephant, standing about 2 m tall at the shoulder, exceeding 4 m in length, and weighing up to 2 t. Despite its bulk, it is quite agile and mobile—it jumps well, can run at speeds of 35-40 km/h, swims expertly, and spends a considerable amount of time in the Water.

Tapirs, found in South and Central America and Southeast Asia, are quite unique; they are roughly the size of an ox or occasionally smaller. Their forelimbs are four-toed, while their hindlimbs are three-toed. The Nose is fused with the upper lip to form a relatively short proboscis, which the animals use to probe objects, grasp them, and guide them into the Mouth.

Tapirs inhabit dense forests near water bodies, feeding on aquatic and riparian vegetation along the banks. Their overall population numbers are low, and they are in need of conservation.