The close of the Cretaceous saw catastrophe. A1l theropods and protobirds failed to pass this boundary. Walking dinosaur costume From what we know, toothed and enantiornithiforme birds did not make it either. In fact, the former may not have made it that far. Only the more modern birds did cross into the Tertiary, though whether they suffered a temporary setback at the time is not known. Many other life forms had trouble at this time as well. The herbivorous dinosaurs bought it, as did some mammals and all pterosaurs. All marine reptiles except the furtles were wiped out. Much other marine life was affected. Plants suffered also. Lizards, furtles, and crocodilians did survive. Again, big questions come up, the most important to us being-what caused predators that had been so successful for 170 million years to vanish?
In one way the answer is obvious. The big predaceous theropods were dependent on the well-being of the herbivores. Realistic dinosaur costume When big herbivore populations crashed, the big predator populations did too. So the fate of herbivorous dinosaurs is a key question, though not the only one. For even with all herbivorous dinosaurs gone, the small protobird theropods should have been able to survive on the mammals and reptiles that were left over. With their initially larger populations, they could better survive disasters than bigger species. And their faster breeding rates would have allowed them to recover more quickly. Small theropods would have had no competition in the early Tertiary. Indeed, they could have dominated the predator niches up until today, evolving new giant species. They could even have spawned new dinosaurian herbivores. But they did not have the chance.