This small freshwater turtle is the most endangered Australian reptile . The flattened carapace appears square from above  and varies in colour from yellow-brown to black depending on the area . The flattened head is covered by a single large bony plate, or scute . Unusually amongst turtles, the female is smaller than the male . The plastron, or undershell, of the western swamp turtle is paler than the carapace and extremely broad ; it often has a pattern of black spots on a yellow background . The short legs are covered with bony plates and the feet are clawed .