A relative of the elephant, manatees are totally aquatic, herbivorous mammals of the family Trichechidae. This group arose 15–20 million years ago during the Miocene period, a time which also favored the development of a tremendous diversity of aquatic plants along the coast of South America. Manatees are adapted to both marine and freshwater habitats and are divided into three distinct species: the Amazonian manatee (Trichechus inunguis), restricted to the freshwaters of the Amazon River; the West African manatee (Trichechus senegalensis), found in the coastal waters from Senegal to Angola; and the West Indian manatee (Trichechus manatus), ranging from the northern South American coast through the Caribbean to the southeastern coastal waters of the United States. Two other species, the dugong (Dugong dugon) and Steller's sea cow (Hydrodamalis gigas), along with the manatees, make up the order Sirenia. Steller's sea cow is now extinct, having been exterminated by man...