Nothosaurs were probably rather like seals in their habits. Placodonts had much more chunky proportions, with some developing very turtle-like proportions. One of the more generalized forms was Placodus which probably ate mollusks. Placodonts were probably similar to walruses and marine turtles in their habits. Nothosaurs and placodonts became extinct at the end of the Triassic.
Ichthyosaurs appear in Early Triassic marine deposits.
They had very porpoise-like proportions and presumably ecological requirements. Lizards evolved in the Triassic and became quite common by its end. Some early forms evolved into gliding forms such as Kuehnosaurus from England and Icarosaurus from New Jersey. Both had a gliding membrane supported by vastly expanded ribs. The Triassic forms died out at the end of the Period.