Psittacosaurus dinosaurs trapped in mudslide triggered by a volcanic eruption, illustration. Events such as this led to the formation of fossils that were uncovered millions of years later. These dinosaurs were herbivores, and their parrot-like beaks may have been used to crack nuts. The even depicted here occured in what is now China. Psittacosaurus existed from 123 to 100 million years ago, during the Early Cretaceous.