All but the leatherback are in the family Chelonioidea. The leatherback belongs to the family Dermochelyidae and is its only member. The leatherback sea turtle is the largest, measuring six or seven feet (2 m) in length at maturity, and three to five feet (1 to 1.5 m) in width, weighing up to 2000 pounds (about 900 kg). Most other species are smaller, being two to four feet in length (0.5 to 1 m) and proportionally less wide. The flatback turtle is found only on the northern coast of Australia.