​The Cretaceous Period (145–66 million years ago) was the last part of the Mesozoic Era. The climate was hot and humid, with lush forests and no polar ice. This period was dominated by iconic dinosaurs like T. rex and Triceratops. Pterosaurs soared above oceans filled with large creatures like Mosasaurus and Plesiosaurus. It ended with a huge asteroid impact, wiping out the dinosaurs and many other species.