Mosasaurs, giant marine reptiles that existed more than 66 million years ago, lived not only in the sea but also in rivers. This is shown by new research based on analyses of a mosasaur tooth found in ...

At the end of the Cretaceous Period, a type of giant reptile called mosasaurs occupied and dominated oceanic food webs. Mosasaurs had long bodies and were related to both snakes and monitor lizards.