Found before the dinosaurs
A huge skull was dug out of a chalk mine at Maastricht in the 1770s, long before any dinosaur was named.
In the sea · Sea reptiles
Mosasaurus
Lizard of the Meuse · MOE-za-SORE-us
A gigantic swimming lizard with a long head, four flippers and a tail with a fluke like a shark's.
- Size
- About 12 to 15m long
- Lived
- About 70 to 66 million years ago
- Found in
- The Netherlands; also North America, Africa and beyond
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To scale
How big was it?
The bars are drawn to the same scale. On these pages the animals are sized in proportion to each other as far as a screen allows: the giants are shrunk a little and the smallest are enlarged, so that you can see them all.
Good to know
Six things about the mosasaurus
A giant lizard
Its closest living relatives are monitor lizards and snakes.
Two sets of teeth
It had a second row of teeth on the roof of its mouth, to stop prey escaping.
A tail like a shark's
Fossils with skin show that the tail bent downwards and carried a fluke.
As long as a bus
It was one of the largest sea reptiles of all time.
A prize of war
The Maastricht skull was seized by French soldiers in 1794 and is still in Paris.
The real thing
Photos of the mosasaurus
Photos are from Wikimedia Commons, used under the free licences shown. They have been resized, and cropped where they appear in link previews.
What it ate
Fish, sharks, turtles, sea birds and other mosasaurs.
How we know
Bite marks on ammonites and turtle shells match its teeth.
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