Liopleurodon

Liopleurodon was an enormous "Pliosaur" from the Jurassic period, living between 165–150 million years ago. It is the only Mesozoic marine reptile to be close to matching the largest whales of today. Its teeth were twice as long as those of Tyrannosaurus rex. They reached sizes of 15 m (50 ft). Exaggeration by the media caused them to be viewed as almost 80 feet (25 meters) in length, an error which was perpetuated in Walking With Dinosaurs. It is still debatable as to how heavy it might have been, but estimates are that it weighed around 150 tons.

About the Liopleurodon in Walking With Dinosaurs

In the popular CGI documentary its food consisted of anything from Ophthalmosaurus to Cryptoclidus.