leatherback, marine turtle, Dermochelys coriacea, found in tropical, subtropical, and temperate waters around the world. The largest of all turtles, it may reach a length of 71/2 ft (230 cm) and weigh 1200 lb (540 kg). Its shell, unlike that of most turtles, has no horny layer; the bone layer is covered with tough, leathery, black skin. Seven bony ridges running the length of the shell give this turtle its distinctive appearance. Highly pelagic turtles, leatherbacks have occasionally been seen as far N as Norway and as far S as New Zealand. They sometimes enter shallow coastal waters, but come ashore only to lay eggs. They are omnivorous feeders. Like other sea turtles, the leatherback is declining in numbers as a result of hunting and egg harvesting. It is classified in the phylum Chordata, subphylum Vertebrata, class Reptilia, order Chelonia, family Dermochelidae.