Leatherback turtles (Dermochelys coriacea) are the largest sea turtles, growing as long as six and a half feet (2 m) and weighing some 2,000 pounds (900 kg). They’re unlike the other marine turtles in two important ways: they have a thick leathery carapace (outer covering) instead of a hard bony shell, and can survive in colder waters, allowing them to feed closer to the North and South poles where other turtles can’t survive. Their jaws are too weak to eat hard-bodied prey, so they mostly eat jellyfish and salps.