Placodus (from , "a plate" and , "tooth") is an extinct genus of marine reptiles belonging to the order Placodontia, which swam in the shallow seas of the middle Triassic period (). Fossils of Placodus have been found in Central Europe (Germany, France, Poland) and China.
Palaeobiology
thumb|left|Restoration
thumb|right|Skull ([[AMNH 4985)]]
thumb|left|upright|Under surface of the upper jaw and palate of Placodus gigas
Placodus had a stocky body with a long tail, and reached a total length of . It had a short neck, and a heavy skull. They were specialized for a durophagous diet of shellfish, such as bivalves. Chisel-like incisors protruded from the anterior margin of the snout, and were probably used to pluck hard-shelled benthic prey from the substrate. The back teeth were broad and flattened, and would have helped to crush the prey. Before the animals' anatomy was known, they were regarded as fishes' teeth. Similar smaller teeth were present on the palatine bones.
Placodus and its relatives were not as well-adapted to aquatic life as some later reptile groups, like the closely related plesiosaurs. Their flattened tails and short legs, which probably ended in webbed feet, would have been their main means of propulsion in the water.