Placochelys and Cyamodus. Psephoderma had a flattened skull and a narrow, straight rostrum. Inside this skull, embedded in the jaws, were rounded teeth specialized for crushing the shellfish it ate. Unlike most placodonts, Psephoderma had a carapace that was divided into two pieces, one on the shoulders and back, another on the rear end. Psephoderma grew to 180 cm long and lived in the Late Triassic (Norian), about 210 million years ago. It was one of the last placodonts to live.