Dugongs are born a pale cream color, but they darken with age to a deep slate gray dorsally and laterally. The short hair is sparsely distributed over the body, save the bristles on the muzzle. The skin is thick, tough and smooth. The front-limbs have evolved into flippers that are 35-45 cm long. These are used for propulsion by young, but the adults use the fluke-like tail for locomotion, using the flippers for steering. Despite its diet, the dugong ha s a relatively simple stomach. The muscular upper lip is cleft and protrudes over the down turned mouth. The lower lip and distal parts of the palate have horny pads used to grasp vegetation, which is then uprooted with the strong upper lip. The dental formula is 0/0 0/0 0/0 2-3/2-3, for a total of 10-14 teeth in adults. The molars are rootless, circular in cross-section and lack enamel. The premaxilla is enlarged and downturned, the nasal bones are absent, the braincase is small and the zygomatic arch is thick and deep. The bones of the skeleton are pachyostotic, which is to say extremely thickened and dense. Adults range in length from 2.4 to 4 m. Sexual dimorphism is either absent or females may slightly outsize males.