What is the Cretaceous Period?
The Cretaceous Period lasted from 144 to 65 million years ago. It was the final period of the Mesozoic Era, the “Age of Dinosaurs.” In the Late Cretaceous Period, animals like Triceratops and T. rex roamed what is today North America. Mammals were also present, but none grew much larger than an opossum. The end of the Cretaceous Period is marked by a mass extinction that wiped out all of the dinosaurs and many other kinds of animals, including mosasaurs (giant swimming reptiles) and pterosaurs (flying reptiles).
