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(platy sternum megacephalum), a reptile of the family Platysternidae, suborder Cryptodira (turtles). It is characterized by a flat, broad shell and by a very large head which cannot be drawn under the shell and is protected by a compact, horny shield. The tail is very long and covered with large scales. Color on top is olive-brown; beneath, yellowish. Total body length is up to 40 cm. It is found mainly in mountain streams of the less-populated part of the Indochinese Peninsula but is everywhere relatively rare. The big-headed turtle swims well in search of food or of the warmth of the sun, and it climbs easily onto shore rocks or tree stumps. It feeds on small marine and terrestrial animals: fishes, mollusks, worms, and the like.