The reptiles who returned to the sea are from the group including fish-shaped ichthyosaurs and long-necked, spindle-shaped plesiosaurs, as well as turtles and lizards.Among them, the ichthyosaurs four legs and tail became like fins, and assumed a form suited for ocean life. Also, the four legs and long tails of the relatives of the lizards adapted to the seas and are believed to have evolved into fins.