The most distinctive feature of the aptly named big-headed turtle (Platysternon megacephalum) is its enormous, triangular head, which is so large in proportion to its body that it cannot be withdrawn into the shell for protection. Instead, the top and sides of the turtle’s head are covered with a large bony ‘roof’ that acts as armour and, unlike most turtles, the skull is solid bone. The upper jaw is hooked and the edges of both jaws are lined with another tough horny covering, leaving only a narrow band of unprotected skin on the cheeks and running from the turtle’s eyes to the corners of its mouth. Together with an oversized head, this odd-shaped turtle can be recognized by its exceptionally long, thin tail and particularly flattened shell, which is somewhat rectangular, being squared-off at the front and more rounded at the back. While the upper shell (carapace) is yellow to dark brown, occasionally with a darker radiating pattern, the lower shell (plastron) is usually yellow, although this varies between the five subspecies. The legs are covered in large scales, as is the long, thin, muscular tail, which is often used to support the animal’s weight like an additional limb.