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Skeleton at the Academy of Natural Sciences, Philadelphia

Mosasaurus, meaning "Muese (river) lizard" is a huge type of marine lizard that ruled the seas during the last age of the dinosaurs, about 70 million years ago.

What was their body shape?[edit | edit source]


Tyrannosaurus Rex

A drawing of a Mosasaurus

Mosasaurus was a type of marine reptile related to monitor lizards. It used its four flippers and shark-like tail to pursue fast-moving prey like turtles, and snapped them up in its immense jaws, before swallowing them whole. It had an average length of 12-15 metres, although a big one could reach over 17 metres.

What did they eat?[edit | edit source]

Mosasaurus was the apex predator of its time, so it feared nothing, except other mosasaurs. Its long jaws were studded with more than 70 razor-sharp teeth, along with an extra set in the roof of its mouth, meaning that there was no escape for anything that crossed its path. We don't know for sure, but it may have had a forked tongue. Its diet included turtles, large fish, other mosasaurs, and it may even have been a cannibal. It also attacked anything that entered the water; even a giant dinosaur such as T. rex would be no match for it.

When did they live?[edit | edit source]

Mosasaurus lived about 70 to 65 million years ago during the late Cretaceous period.

What was their habitat?[edit | edit source]

Mosasaurus called the Western Interior Seaway its home, and probably favored the warmer climates of North America. The coral reefs would have been the perfect place to ambush fish and other food items.

How were they discovered?[edit | edit source]

An important discovery

The first Mosasaurus fossils were found in 1764, and were thought to come from a whale. In 1778 the remains were identified by physician Johann Hoffman as being from a crocodile. In 1798 a scientist, Adriaan Camper finally identified it for what it was, a giant monitor lizard. In 1808 the well-known George Cuvier recognized the fossil as that of an extinct creature, named "The Great Fossil Animal of Maastricht". In 1829, famous anatomist Richard Owen classified it as Mosasaurus hofmannii.

We know more about Mosasaurus now than we used to 200 years ago. Recently, we have found fossilized skin, an imprint of a tail fluke and even the bony rings of the animal's throat. The tiny scales on the animal's skin are roughly diamond-shaped.

In popular culture[edit | edit source]

Mosasaurus makes an appearance in the film Jurassic World (2015), where it is fed a great white shark as part of a SeaWorld-style feeding show. It is shown as being twice its real size, and with crocodilian back ridges. It also features in the sequel, Jurassic World: Fallen Kingdom(2018), attacking a mini-sub. It is also shown in documentaries and on postage stamps.

What do we need to know?[edit | edit source]

  • What color were they?

We know from pigments that the top was a darker shade than the bottom, but not exactly what color.

  • How fast did it swim?
  • Was it really the biggest predator?