Seaturtles: Cheloniidae

The seaturtles are large animals that live in the ocean. Their upper shell, or carapace (KARE-a-pays), is quite flat rather than highly rounded. The lower shell, or plastron (PLAS-trun), is a bit smaller than in most turtles and attaches to the upper shell by tough but flexible tissues called ligaments (LIH-guh-ments), rather than the bony bridge common to land turtles. Seaturtles are excellent swimmers, gliding through the water with sweeps of their large, broad, and powerful front limbs, which look like flippers or paddles. Unlike many other turtles, they cannot retract, or pull back, their limbs or heads into their shells. The largest members of the family, the leatherback seaturtles, tip the scales at half a ton (454 kilograms) or more. The leatherbacks have a carapace that measures 6 to 7 feet (1.8–2.1 meters) in length.