Late Cretaceous, ~80–66 million years agoReputable sourceWell documented
Mosasaurs, the Last Sea Monsters
On the timeline · around Late Cretaceous, ~80–66 million years ago · The Cretaceous
What happened
As the ichthyosaurs faded, giant marine lizards called mosasaurs rose to rule the Late Cretaceous oceans. Powerful swimmers related to today's monitor lizards and snakes, they were the top predators of the seas.
Why it matters
Mosasaurs dominated the oceans for the final tens of millions of years of the Mesozoic and then vanished in the same mass extinction that ended the dinosaurs.