The period known as the Cretaceous Period ended 65 million years ago with the extinction of the dinosaurs and many, many other prehistoric life forms. No one knows exactly what brought on this disaster. One theory is that a huge asteroid hit the Earth, while another is that there was a rapid increase in volcanic activity. There were severe climate changes, and the Age of the Reptiles came to an end, to be followed by the Age of Mammals.
Crocodiles and other members of the crocodile family were however, able to survive the disaster. One explanation for their survival is that, crocodiles belong to the community of freshwater vertebrates whose food chain was not so severely affected, since they did not depend on marine plankton or flowering plants that had completely disappeared. Whatever the reason, the fact remains that while huge dinosaurs were wiped off the face of the Earth, the hardy crocodile adjusted to the new conditions on Earth, and survived.