The leatherback sea turtle, sometimes called the lute turtle or leathery turtle, is the largest of all living turtles and is the fourth-heaviest modern reptile behind three crocodiles. It is the only living species in the genus Dermochelys. It can easily be differentiated from other modern sea turtles by its lack of a bony shell. Instead, its carapace is covered by skin and oily flesh. D. coriacea is the only extant member of the family Dermochelyidae.
Relatives of modern leatherback turtles have existed in some form since the first true sea turtles evolved over 110 million years ago during the Cretaceous period. The dermochelyids are close relatives of the family Cheloniidae, which contains the other six extant sea turtle species. However, their sister taxon is the extinct family Protostegidae which included other species not having a hard carapace.
Leatherback turtles have the most hydrodynamic body design of any sea turtle, with a large, teardrop-shaped body. A large pair of front flippers power the turtles through the water. Like other sea turtles, the leatherback has flattened fore limbs adapted for swimming in the open ocean. Claws are absent from both pairs of flippers. The leatherback's flippers are the largest in proportion to its body among extant sea turtles. Leatherback's front flippers can grow up to 2.7 m in large specimens, the largest flippers of any sea turtle.
Leatherback turtles are one of the deepest-diving marine animals. Individuals have been recorded diving to depths as great as 1,280 m. Typical dive durations are between 3 and 8 minutes, with dives of 30–70 minutes occurring infrequently.
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