Family Trichechidae - Manatees (3 species in 1 genus)
Manatees are found in tropical and subtropical areas and are very sensitive to cold. They are characterized by a horizontally flattened, rounded tail (as opposed to the whale-like flukes of dugongs). With only 6 cervical vertebrae, manatees are among the few groups of mammals that diverge from the normal mammalian number of 7. They are also unique in that their teeth are replaced throughout life with new ones from the rear of the mouth.
Genus Trichechus containing 3 species:
Trichechus inunguis (Amazonian manatee)
Trichechus manatus (West Indian manatee)
Trichechus senegalensis (West African manatee)