Trichechus
A genus of the order Sirenia comprising what are commonly called manatees. The distinguishing characteristics include a tail that is not notched, a short nasal cavity, the absence of nasal bones, and enamel-covered teeth. Members of this genus are found in marine bays and/or sluggish rivers, usually in turbid water. (From Scott, Concise Encyclopedia Biology, 1996)
Trichechus inunguis
Trichechus manatus
Sirenia
An order of heavy-bodied, slow-moving, completely aquatic, herbivorous mammals. The body is fusiform, plump, and hairless, except for bristles on the snout. Hindlimbs are absent, the forelimbs are modified to flippers, and the tail is a horizontal fluke. (From Scott, Concise Encyclopedia Biology, 1996)
Dugong
A genus of the order Sirenia characterized by a notched tail, the presence of nasal bones and a long nasal cavity, and large columnar teeth lacking enamel. Dugongs inhabit the coastal waters of the Indian Ocean, Red Sea, and the Malay Archipelago. (From Scott, Concise Encyclopedia Biology, 1996)