Mosasaurus

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Mosasaurus
Fossil range: Late Cretaceous

Mosasaurus hoffmanni and Globidens aegypticus

Conservation status

Extinct (fossil)

Scientific classification

Kingdom:	Animalia
Phylum:	Chordata
Class:	Sauropsida
Order:	Squamata
Suborder:	Lacertilia
Family:	Mosasauridae
Genus:	Mosasaurus

Species

M. copeanus
M. crassidens
M. hoffmanni
M. meirsii
M. princeps
M. beaugei
M. conodon

Mosasaurus (IPA pronunciation: ['mozəˌsɔrʊs]) "lizard of the Meuse" was a genus of mosasaur, a carnivorous, aquatic lizard, somewhat resembling a flippered crocodile, with elongated heavy jaws. The genus lived in the Maastrichtian age of the Cretaceous period (Mesozoic era), around 70-65 millions years ago. The name means "Meuse lizard", because it was found in the Meuse River (Latin Mosa + Greek sauros lizard). As with all mosasaurs, their legs and feet are modified into paddle-like flippers, with the forelimbs larger than the hindlimbs. The first mosasaur ever discovered, Mosasaurus hoffmanni, was excavated in a mine near Maastricht, the Netherlands in the 1770s. The beast was later named for the nearby river Meuse. Like its relatives Tylosaurus and Hainosaurus, Mosasaurus reached lengths of about 15 metres. However, Mosasaurus was much more robust than tylosaurine mosasaurs, at some double the weight of a mosasaur of the same length. In life, a 10 m long Mosasaurus was as heavy as a 15 m long Tylosaurus.

Mosasaurus was among the last mosasaur genera, and among the largest, being smaller and shorter only than the mosasaurs of the genera Tylosaurus and Hainosaurus. The skull was more robustly built than 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. Because of its robust skull and tightly articulating jaws, Mosasaurus was unable to swallow prey-items whole in the manner of earlier mosasaurs, such as Tylosaurus. Instead, with the aid of its curved, knife-like teeth, Mosasaurus was able to tear its prey into more manageable pieces that could be more easily swallowed.

As mentioned before, Mosasaurus is named after the town of Maastricht, located at the most Southern tip of the Netherlands. The city is largely built with blocks of limestone from the town's quarry. In 1770, the local Dutch army physician, Dr Hoffmann, who had developed an interest in the strange bones that kept showing up in these blocks of limestone, paid the quarrymen extra to look out for especially large specimens. The best of these was found in 1774, and it was named Mosasaurus hoffmanni. It was a very controversial find, as the skull belonged clearly to a species that no longer existed on earth, and it raised the first speculations on the possibility of animal species going extinct. The idea of extinction paved the way for the theory of "several creations", one of the predecessors of the evolution theory. A few years after the find, the French armies occupied Maastricht and the fossil skull was taken to Paris, where it is still on display in the "Muséum National d'Histoire Naturelle",

In 1998, another, even bigger and more intact fossil Mosasaurus skull was found in the Maastricht limestone quarries. It was nicknamed " Ber" and it is currently on display in the Maastricht Natural History Museum,