A carnivorous marine mammal (family Phocidae) that has no external ears, a small tail, and hindlimbs that cannot be turned forwards to aid movement on land. The forelimbs are used for steering. Seals feed mainly on fish and invertebrates, but some species eat marine plants and the leopard seal (Hydrurga leptonux) feeds on penguins. There are 15 extant genera of 18 species found in all oceans and in the Caspian Sea and Lake Baikal.