The leatherback sea turtle (Dermochelys coriacea) is an animal of extremes. The largest of the sea turtles, they can reach 2,019 pounds (916 kg), and the species comes from a different lineage than the other sea turtles alive today.
While other turtle species have a hard shell completely fused around the outside of their body for protection, the leatherback's shell is flexible and is covered in a layer of fat and skin.
As a reptile, you would expect the leatherback to be cold-blooded, but here it is also different from the norm! Because of its layer of fat, and its large size, the leatherback sea turtle is so well insulated that when it swims it generates enough heat to keep its body temperature above the temperature of the surrounding water. This means that, while other sea turtles are confined to warm tropical waters, leatherbacks can travel into cooler temperate areas -- such as off the coast of California -- where the waters are rich in nutrients and full of their favorite food, jellies.