Extinct aquatic mammal (Hydrodamalis gigas) that lived around islands in the Bering Sea. It was discovered in 1741 and described by a member of Vitus Bering's expedition. At least 24 ft (7.5 m) long, it had no teeth, a small head, and a broad, horizontal, forked tail fluke; its dark brown skin was sometimes streaked or spotted with white. It browsed on seaweed. Russian sealers hunted it for food and fur; by 1768 the entire population, estimated at about 5,000, had been exterminated. The term also refers to dugongs and manatees.