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a family of large extinct aquatic lizards that lived in the Late Cretaceous period. They were similar to the monitors, which originated from the primitive Mosasauridae. Body length, 10–12 m. The head and body were long, the paired limbs were flipper-like with an increased number of phalanges, and the tail was long and laterally compressed. The animals had powerful jaws and large sharp teeth. These lizards were predators, feeding primarily on fish, mollusks, and echinoderms. They lived in shallow subtropical seas. The remains of Mosasauridae have been found in Upper Cretaceous deposits on all continents except Australia.