These incredible dinosaurs lived during the Late Cretaceous period , about 70-66 million years ago. Most of the fossils from the Mosasaurus were found in Europe and North America. The powerful carnivores that reached lengths of up to 56 feet roamed the oceans near the surface where they would hunt their prey of ammonites, birds, fish and turtles. Mosasaurus Tooth will measure between 25mm and up to 30mm in length.