Mosasaurs were the largest lizards that ever evolved and attained lengths of almost 60 feet with a skull 6 foot long! The Mosasaur was a powerful swimmer who spent its entire life in the sea. Mosasaurs had long and powerful bodies whose tails and limbs were adapted for swimming. They probably swam by moving their long body in a snake-like way, also using their finned tail to propel them for-wards. They steered with small, webbed feet. These reptiles lived during the latter part of the Cretaceous period of the Mesozoic Era (from about 100 million years ago to about 65 million years ago) Mosasaurs were carnivores eating fish, sea urchins, turtles, and shellfish. They lived at the same time as many of the dinosaurs, and like the dinosaurs became extinct during the Cretaceous-Tertiary mass extinction.