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Mosasaurus

The Mosasaurus is an extinct species of huge carnivorous aquatic lizards. The meaning of the name Mosasaurus, "Lizard of the Meuse", refers to the place where the very first specimens of this dinosaur were found: the river Meuse in Europe. This marine reptile lived in the Upper Cretaceous period, between 70 and 65 million years ago, in the vast majority of the world's oceans but mainly in the seas of Europe and North America.

Jurassic World greatly exaggerated the proportions of the Mosasaurus

Like the Velociraptor, the proportions of the Mosasaurus have been greatly exaggerated in the film Jurassic World where it is possible to observe the latter swallowing a large white shark and dragging a gigantic Indominus Rex in the waters. The real Mosasaurus, which weighed about 15 tons, was much less impressive than its cinematic depiction. But where does the sensationalism in Hollywood end?

Curious mixture between a fish and a snake

It is to Georges Cuvier that we owe the honor of having established that this formidable giant marine reptile of nearly 50 feet long (approximately 18 meters) belonged to the family of mosasaurs. These dinosaurs are recognizable by the look of their heads which is rather broad and resembles that of a crocodile and by the shape of their bodies which is a curious mixture of fish and snake. As with many other mosasaurid species, the legs and feet of the Mosasaurus were modified into hydrodynamic fins that allowed it to navigate effortlessly through the waters at high speeds. Since the Mosasaurus was carnivorous, his jaw was very powerful and filled with razor sharp teeths. These teeths could eviscerate everything that this animal wanted to eat.

Although Mosasaurus was suitable for aquatic life, he was able to breathe in the open air.

First discoveries

The earliest remains of Mosasaurus were discovered long before society was educated on evolution, dinosaurs and marine reptiles. In the late 18th century, a fragment of skull was found in a chalk quarry on a hill near Maastricht in the Netherlands. A few years later the fossil was collected by Lieutenant Jean Baptiste Drouin. It was first thought that these fossils probably came from fish, whales or even crocodiles. The closest assumption, however, was made by the naturalist Aadrian Camper, who assumed that these were monitor lizard bones. More fossils eventually begin to quietly emerge and some 60 years later Gideon Mantell officially named the marine reptile Mosasaurus.

The discovery of Mosasaurus is a major scientific breakthrough in history since it was when Georges Cuvier realized that this fossil belonged to an aquatic lizard that he understood that other species now extinct had already lived on Earth at a certain time. This kind of notion went against the dominant religious thought of the time and was very controversial.

Lars the Mosasaurus hoffmannii

Skeleton fossil of Mosasaurus hoffmannii
Mosasaurus hoffmannii

More recently, a 14-year-old amateur paleontologist and his father discovered a fossil of Mosasaurus hoffmani near Maastricht. The fossil has been named Lars (referring to the discoverer Lars Barten) and is exhibited at the Museum of Natural History of Maastricht.

Ancestors

Galapagos Islands Marine Iguana
Galapagos Islands Marine Iguana

The ancestors of the Mosasaurus were probably similar to the marine iguanas of the present Galapagos Islands; they were earthly creatures but went to the ocean to feed. These aquatic lizards gave birth to mosasaurs about 90 million years ago in waters already dominated by sharks that were then at the top of the aquatic food chain.

Mosasaurus is responsible for the disappearance of the Ginsu Shark

Requin ginsu

Over the millennia, the Mosasaurs have grown enormously (reaching more than 50 feet) and caused the disappearance of the Ginsu Shark (Cretoxyrhina mantelli), which was comparable in size to the Great White Shark. The reign of the Mosasaurus, however, was short-lived since it disappeared along with all the other dinosaurs during the Cretaceous-Tertiary extinction.

Related to Komodo Dragon

Komodo Dragon

The mosasaurs were only distant relatives with the pliosaurs and plesiosaurs that preceded them and supplanted them for the dominance of the oceans at the time of the Upper Cretaceous. Evolutionary biologists believe that the Mosasaurus is close relatives of modern snakes and monitor lizards like the Komodo Dragon.

Evolution

In the space of 27 million years, these predators have transformed themselves from terrestrial animals with limbs to aquatic lizards. Studies using anatomical comparisons with sharks and ichthyosaurs have shown that changes in the tail, which became more powerful and more flexible, as well as modifications to the extremities that turned into paddles have allowed the Mosasaurus to adapt and conquer this new environment. The tail of the mosasaurs was very similar to that of whales, sharks and ichthyosaurs (another aquatic lizard that disappeared from the Cretaceous oceans before the arrival of the Mosasaurus).

Habitat and food

The Mosasaurus is thought to have been hunting near the surface of the water and feeding mainly on seabirds, sharks, large fish, seafood, squid, plesiosaurs, pterosaurs and even other mosasaurs. In general, it is conceivable that this apex predator of the prehistoric depths feasted on almost anything living in the ocean. The Mosasaurus had a second set of teeth in his upper palace that ensured preys it was trying to swallow had no chance of escaping. It is interesting to note that although Mosasaurus lived alongside dinosaurs, it technically wasn’t one but an aquatic lizard.

Classification

The Mosasaurus is part of a family of giant marine reptiles related to monitor lizards and snakes. It is frequently confused with plesiosaurs and ichthyosaurs or considered a dinosaur.

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