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.