Mosasaurus, the "Lizard of the Meuse River," was amongst the last of the  mosasaurs before the Cretaceous- Paleogene mass extinction event. With the largest species being up to seventeen meters long, Mosasaurus  was a force of nature within the  oceans of the Cretaceous. Mosasaurus was more robustly built compared to  its tylosaurine relatives. Its  strong tail provided propulsion in the water while its stiff body  reduced drag. It suffered from poor  binocular vision and smell, which  meant it likely lived near the ocean  surface where there is more light  and less pressure instead of in deeper waters.  Policing the waters of North America and Western Europe, Mosasaurus was  an undisputed king of the seas. As  an apex predator, all trembled in its presence. Armed and dangerous, it was a carnivore and piscivore, feeding upon marine reptiles and various fishes in the Cretaceous  Period with its massive, conical  teeth. It preyed upon turtles and  ammonites in addition to plesiosaurs  and smaller fellow mosasaurids and   at the surface of the ocean. With  its paddle-like fins and strong  tail, the water was almost always  bloody in the world of the  Mosasaurs.