Prehistoric Mosasaur Dinosaur Jaw Section with huge fossil teeth and full root matrix in the original jaw bone. Measures 7" inches. This is a rare full grown adult tooth and jaw section specimen. Globidens Mosasaur: Mosasaurs are an extinct group of large marine dinosaurs that probably evolved from an extinct group of aquatic lizards, aigialosaurs in the Early Cretaceous period, 100 million years ago, specifically during the last 20 million years of the Cretaceous period. After the extinction of ichthyosaurs & the decline of plesiosaurs, Mosasaurs became one of the most dominant marine predators. They breathed air & were powerful swimmers, living in the warm shallow inland seas during the Late Cretaceous & they gave birth to live young rather than returning to the shore to lay eggs. Mosasaurs ate mollusks, which were abundant in the Cretaceous seas, as well as fish, turtles & even sharks. They had double-hinged jaws & flexible skulls, resembling those of modern reptiles. Large mosasaurs were typically longer than 25 feet. Currently the largest Mosasaur skeleton in the world on display is just over 43 ft long.