The Amazonian manatee (Trichechus inunguis) is a species of manatee that lives in the Amazon Basin in Brazil, Peru, Colombia and Ecuador. It has thin, wrinkled brownish or gray colored skin, with fine hairs scattered over its body and a white chest patch. It is the smallest of the three extant species of manatee. Taxonomy The specific name, inunguis is Latin for "nailless." The genus name Trichechus, comes from Latin meaning "hair", referencing the whiskers around the manatee's mouth. Physical characteristics The Amazonian manatee is the smallest member of the manatee family and can be distinguished by its smoother rubbery skin and lack of vestigial nails on its flippers. Ranges of body weight and size observed are and for captive males, and for captive females, and and for free-ranging manatees, respectively. The maximum actual Amazonian manatee weight reported is . Calves of the species are born weighing and long. The Amazonian Manatees increase in length approximately 1.6-2.0 mm per day. This length is measured along the curvature of the body so absolute length can differ between individuals. As calves, they gain an average of 1 kilogram per week. Amazonian manatees are large, cylindrically shaped mammals, with forelimbs modified into flippers, no free hind-limbs, and the rear of the body in the form of a flat, rounded, horizontal paddle. The flexible flippers are used for aiding motion over the bottom, scratching, touching, and even embracing other manatees, and moving food into and cleaning the mouth. The manatee's upper lip is modified into a large bristly surface, which is deeply divided. It can move each side of the lips independently while feeding. The general coloration is grey, and most Amazonian manatees have a distinct white or bright pink patch on the breast. Amazonian manatees, similar to all living manatee species in the family Trichechidae, have polyphyodont teeth. Their teeth are continuously replaced horizontally from the caudal portion of the jaw to the rostral portion throughout the manatee's life, a unique trait among mammals. Only the closest living relative of order Sirenia, elephants, show a similar characteristic of teeth replacement, but elephants have a limited set of these replacement teeth. As the teeth migrate rostrally in the manatee, the roots will be resorbed and the thin enamel will wear down until the tooth is eventually shed. Referred to as cheek teeth, differentiation of manatee teeth into molars and premolars has not occurred, and