Pliosaurs were relatives of the plesiosaurs, but they had shorter necks and massive skulls armed with enormous teeth. They were the largest and most powerful predators ever known. Some types, such as Liopleurodon, reached a length of 13 m. The head of another species, called Kronosaurus, was nearly 2.4 m long. These pliosaurs played a similar role in the seas to that of modern killer whales.
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