decades, allowing for easy identification. The Florida manatee has three to four nails on each flipper. The West Indian manatee has a prehensile snout, like their relative the elephant, for grabbing vegetation and bringing it into their mouths. Manatees have six to eight molariform teeth in each jaw quadrant. These molariform teeth are generated at the back of the mouth and slowly migrate towards the front of the mouth, at a rate of 1–2 mm per month, where they then fall out. This tooth ‘conveyor belt’ provides unlimited tooth production which is beneficial for the manatee which feeds on vegetation four to eight hours per day and consumes 5-10% of its body weight per day. Manatees have 3–5 cm hairs that cover their whole body and provide somatosensory information. Manatee bones are dense and solid which allows them to act as ballast and promote negative buoyancy. This helps counteract the positive buoyancy which comes from their high fat content. These two buoyancy counterparts, along with air in the lungs, helps manatees achieve neutral buoyancy in the water. This makes breathing, foraging, and swimming easier for the manatee. Manatees are unique, compared to other mammals, in that they have a longitudinally oriented diaphragm that is split in half to form two hemidiaphragms. Each hemidiaphragm is capable of independent muscular contractions. Distribution and habitat The West Indian manatee inhabits mostly shallow coastal areas, including rivers and estuaries. Manatees can withstand large changes in salinity and are found in both freshwater and saltwater. Manatees' extremely low metabolic rate and lack of a thick layer of insulating body fat limits them to locations with warm waters, including tropical regions. The Florida subspecies is primarily found along the Florida coast, but has been spotted as far north as Dennis, Massachusetts, as well as along the Gulf Coast of Texas. Concerning their forays inland, a manatee was once spotted in the Wolf River (near where it enters the Mississippi) in Memphis, Tennessee, in 2006: a distance of over 700 river miles from the Gulf of Mexico. The Antillean subspecies has a sparse distribution throughout the Caribbean, ranging as far north as Mexico and as far south as Brazil. An analysis of mitochondrial DNA patterns indicates there are actually three primary geographic groups of the West Indian manatee: (i) Florida and the Greater Antilles; (ii) Mexico, Central America and northern South America; and (iii) northeastern South America.