Ichthyosauria

Another subclass, Ichthyosauria, restricted to the Mesozoic Age, were large, swimming, marine "fish lizards" with a somewhat whalelike form, the front limbs transformed into paddles, and the snout in the form of a long bill filled with sharp teeth. They lived on fishes, cuttlefish, mollusks, etc., and had the general habits of sharks. They died out early in the Cretaceous epoch, and left no descendants.