Sirenia

Sirenia, order of aquatic herbivorous mammals, including the dugong, the manatee, and the extinct Steller's sea cow. The term sea cow is also popularly used for the dugong and the manatee; they attain a length of 2.4 to 4.5 m (8 to 15 ft) and superficially resemble the walrus. The dugong has a bilobed tail fin; that of the manatee is broad and rounded. The dugong inhabits the Red Sea, the Indian Ocean, and the coastal waters north of Australia. Manatees are found in the warm waters of the Atlantic Ocean off the American and African coasts. Both dugongs and manatees may also be found far from the ocean in inland rivers and lakes. Steller's sea cows inhabited the Bering Sea.