The reptiles not only dominated the land, but some even returned to live in the sea. In the Triassic and Jurassic periods, two important groups of marine reptiles, the plesiosaurs and the ichthyosaurs, evolved. These reptiles were well adapted to a seagoing life with their streamlined shape and paddle-like limbs. They existed mainly on a diet of fish and ammonites but often fed on one another.
(A) FISHLIKE REPTILES
Ichthyosaurs were the most fishlike reptiles. Ichthyosaurus looked somewhat like a shark or even a dolphin.
(B) LONG NECKS
Elasmosaurs, such as Cryptoclidus, were long-necked plesiosaurs.
(C) SHORT NECKS
Pliosaurs, such as Peloneustes, were short-necked, big-headed, whalelike plesiosaurs.
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