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Mosasaurs, giant marine reptiles from prehistoric times, also lived in rivers. A team of Dutch, American and Swedish researchers discovered this when analyzing a tooth from such a mosasaur.
The mosasaur was a prehistoric reptile with a long tail, small fins and a large mouth full of sharp teeth. The beast could grow up to 11 meters long. Until now, it was thought that this species could only be found in the sea.
But the research team, including Dutch paleontologist Melanie During, showed that mosasaurs adapted to freshwater in the last million years before their extinction.
The mosasaur – also called the Maas lizard – was found in many places in the world, but was named after the Latin name for the Maas. Dozens of remains have been found in the Maastricht area. Between 70 and 66 million years ago, there was a subtropical Cretaceous Sea in South Limburg in that area where mosasaurs also swam around.
Chemical composition
The tooth was discovered three years ago in a river deposit in the US state of North Dakota. It lay near, among other things, a T. rex tooth and a piece of the jaw of a freshwater crocodile.
“That was just in the middle of the continent at the time,” During explained in the radio program Early Birds. “There were some rivers, but there was no sea. So we thought: what is that tooth doing there?”
The chemical composition of tooth enamel was compared in a laboratory at the Vrije Universiteit Amsterdam, the study states. “I measured the tooth geochemically in many different ways,” says During. “Everything points to freshwater.” Two other mosasaur teeth were also examined. These were found nearby at slightly older sites in North Dakota. There they saw similar traces of freshwater.
Last year, a gigantic skeleton of a mosasaur was exhibited in the Maastricht Natural History Museum. It is 66 million years old.
The constructed skeleton is the first and only full-size in the world:
Mosasaurus Bèr can be seen in full size in Maastricht
