A small group of marine reptiles forming part of the Sauropterygia, known only from deposits of Triassic age in Europe, the Near East (Israel), North Africa (Tunisia), and China. The earliest occurrence of placodonts is in the uppermost Lower Triassic (upper Buntsandstein) of Upper Silesia (Poland); their latest occurrence is in the very late Triassic (Rhaetian) of the Southern Alps. Placodonts are reptiles with a grossly specialized dentition—flat-crowned teeth located in both the upper and lower jaws and on the palate—that functioned as a crushing device for hard-shelled invertebrate prey such as brachiopods, gastropods, clams, and cephalopods (see illustration).