Introduction:
This group of reptiles is unusual because its skeleton forms a protective box around its soft body tissues. The exoskeleton (outer layer) consists of a shell covered with a horny layer or turtle shell. The endoskeleton (inner skeleton) is bony and the ribs, backbone, pectoral girdle (shoulder blade) and pelvic (hip) girdle are fused to the inner layer of the exoskeleton. The overall body is shortened and broadened when compared to other reptiles.

In sea turtles, the front limbs are specially adapted for swimming and are paddle like. The hind limbs also show some adaptation for swimming but are mainly used for steering. Unlike their close relative, the tortoise, a sea turtle cannot withdraw its head into its shell.