Sirenians

Once an order with five species, Sirenia now has four: three species of manatee (genus Trichechus) and one of dugong (genus Dugong). The fifth species, the Steller's sea cow, was hunted to extinction in the early 18th century.

Sirenians swim in the coastal waters of Central and South America, Asia, India and Africa. The dugong inhabits marine waters, while the manatee prefers freshwater coastal rivers and estuaries. Size is the only defense of sirenians: Adults range from 500 to 35,000 pounds (230 to 1,600 kg). The forerunners of sirenians are believed to have descended from an ancestor shared with elephants. Resembling a cross between a seal and a hippopotamus, the sirenian has a streamlined body with no external ears, or pinnae. Its nostrils are located on top of the head. Sensory bristles on its large upper snout are similar to those of a pig or a cow.

The Sirenian Family Tree

order: sirenia
(5 species)

family: dugongidae dugongs, sea cows
trichechidae manatees

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