The Amazonian manatee is a species of manatee of the order Sirenia. It is found living in the freshwater habitats of the Amazon Basin in Brazil, Peru, Colombia, Ecuador, Guyana, and Venezuela. Though, it is estimated if current harvest levels are mainainted in Ecuador, it will be gone within 10-15 years. Its color is grey, but sometimes appears to be a brownish grey. It has thick, wrinkled skin, and is almost hairless, but has "whiskers" around its mouth. It also has a distinct white breast patch, with fine hairs scattered over its body. It lacks significant predation, other than being occasionally hunted by humans, usually with harpoons. The manatees themselves feed on a variety of aquatic macrophytes, including aroids, grasses, bladderwarts, hornworts, water lilies, and particularly, water hyacinths.
An almost unique feature of the manatee is the constant replacement of molar teeth; new teeth enter at the back of the jaw and replace old and worn teeth at the front. The order's closest relatives, the elephants, also have teeth that get replaced, but have only a limited set of these replacement teeth.
The Amazonian manatee is the second-smallest species of manatee after the recently discovered dwarf manatee. It may reach a length of 2.8 m . Females are typically larger than males, and can weigh 360 to 540 kg . Unlike the ), it lacks nails on the end of most flippers.
Recently, a closely related, but far smaller species, the dwarf manatee , has been described from Brazil by Marc van Roosmalen. Called the ''peixe-boi anão'' in Brazilian Portuguese, it is about 130 cm long and lives in fast-flowing streams. Its validity has later been questioned, with some believing it to be an immature Amazonian manatee.