It was a type of pliosaur, or short-necked plesiosaur. Pliosaurs are a group of plesiosaurs.
Plesiosaurs are one of a type of reptiles that returned to the sea.
It had four large paddle-shaped limbs, which made it a powerful swimmer. At almost 25 m long Liopleurodon was the biggest carnivore that ever existed. It had an enormous 3 metre long mouth which contained teeth twice as long as those of Tyrannosaurus . These were arranged in a distinctive rosette at the end of its snout. The remains of Liopleurodon attacks are also preserved in the fossil record.