musk ox, hoofed ruminant mammal, Ovibos moschatus, found in arctic North America and Greenland. The northernmost member of the cattle family (though it is not closely related to true cattle), the musk ox grazes on the stunted vegetation of the tundra. It was exterminated in Alaska about the middle of the 19th cent. but was later restored there on Nunivak island. Its stoutly built body, about 4 ft (120 cm) at the shoulder in the male, is covered by a long, shaggy, brown to black coat, which conceals the short tail and the upper part of the short legs. The male has a musky odor during the mating season. The horns are broad and flattened and nearly meet across the forehead at the base. They extend out from the sides of the head, curving downward and then upward in a hook. The hooves are very large and widely splayed, an adaptation to walking on snow. Musk oxen live in herds of 10 to 20 individuals in summer and up to 100 in winter. When in danger the herd forms a circle, horns pointing outward, with the young in the center. The chief enemy of the musk ox, besides Native Americans and Eskimos who hunt it for flesh and fur, is the wolf. The musk ox is classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Artiodactyla, family Bovidae.