Dinosaurs > Mosasaurus

Mosasaurus, meaning “lizard of the Meuse River”, is a genus of mosasaur, carnivorous, aquatic lizards, somewhat resembling flippered crocodiles, with elongated heavy jaws. The genus existed during the Maastrichtian age of the Cretaceous period (Mesozoic era), around 70–66 million years ago in the area of modern Western Europe and North America. The name means “Meuse lizard”, as the first specimen was found near the Meuse River.

As with most mosasaurs, their legs and feet are modified into hydrofoil-like flippers, with the forelimbs larger than the hindlimbs. Mosasaurus reached lengths of about 18 metres (59 ft), somewhat longer than its American relatives Tylosaurus and Hainosaurus. However, Mosasaurus was more robust than the somewhat smaller sized tylosaurine mosasaurs.

Mosasaurus was among the last mosasaur genera, and among the largest. The skull was more robustly built than in other mosasaurs, as the mandibles articulated very tightly with the skull. It had a deep, barrel-shaped body, and with its fairly large eyes, poor binocular vision, and poorly developed olfactory bulbs, experts believe that Mosasaurus lived near the ocean surface, where it preyed on fish, turtles, ammonites, and possibly smaller mosasaurs. The animal remained near the surface and although it was able to dive, it evidentially did not venture into deeper waters.

The skull of Mosasaurus tapered off into a short, conical process, and the jaws were armed with massive, sharp, conical teeth. Their paddle-like limbs had five digits in front and four in back. The trunk terminated in a strong tail which, together with serpentine undulation of the whole body, contributed far more to the animal’s locomotion than did the limbs.


Clade: Reptilia
Suborder: Squamata
Family: Mosasauridae

Size: 18 m (59 ft) long

Weight: 15 metric tons

When: Cretaceous Period
70 to 66 million years ago

Where: North America, Western Europe

Diet: Carnivore

The family Mosasauridae is split into several subfamilies, with Mosasaurus being placed within Mosasaurinae. This subfamily, in turn, is further split into smaller tribes, with Mosasaurus being grouped with Clidastes, Moanasaurus, and Liodon in the tribe Mosasaurini.

Since the genus was first named in the early 19th century, numerous species have been assigned to Mosasaurus. However, only five are currently recognized as valid by most researchers: M. hoffmannii Mantell, 1829 (the type species), M. conodon Cope, 1881, M. lemonnieri Dollo, 1889, M. missouriensis (Harlan, 1834), and M. beaugei Arambourg, 1952.

Mosasaurs probably evolved from semiaquatic squamates known as aigialosaurs, which were more similar in appearance to modern-day monitor lizards, in the Early Cretaceous. During the last 20 million years of the Cretaceous period (Turonian-Maastrichtian), with the extinction of the ichthyosaurs and decline of plesiosaurs, mosasaurs became the dominant marine predators.

Source: Wikipedia