Taking place from 145 million to 65 million years ago, the Cretaceous period marked the end of an era. For many millenia, the dinosaurs ruled the Earth. But now, their run was nearing it's end, as at the end of the Cretaceous, a massive asteroid struck the planet, killing not just the dinosaurs, but also the pterosaurs and giant marine reptiles. That said, however, the Cretaceous still had a massive variety of amazing creatures, and for millions of years, these animals still ruled the world.