Hoof

A hoof (plural hooves or hoofs) is the tip of a toe of an ungulate mammal, strengthened by a thick and horny keratin covering.

Artiodactyls are even-toed ungulates, meaning that these species have an even number of digits on each foot. Ruminants, with two main digits, are the largest group. Examples include deer, bison, cattle, goats and sheep, Perissodactyls walk on an odd number of toes. Examples of perissodactyl mammals are horses, rhinoceroses and tapirs.

Hooves are generally cited as limb structures restricted to placental mammals, which unlike other mammal groups undergo prolonged pregnancies. However, the marsupial Chaeropus had hooves.