This lineage shows that the ancestors of C. diegosuarezi were likely carnivores. As for why some of them switched to an all-plant diet, Baron explained that during the Late Triassic–Early Jurassic period, Earth’s single continent Pangea was starting to break up.
“When this break up happened, new shallow seas spread between the newly created continents, and so more moisture reached what used to be inland areas,” Baron said. “As a result, more plant life started to appear and spread around the world. I think that this increase in plant life drove the evolution of, and increase in, herbivory in the dinosaur groups.”
“Many predators no doubt preyed upon this increased number of herbivores too," he added, "and we also see an increase in the body size and diversity of the theropod (meat eating) dinosaurs.”
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By the late Cretaceous, the “king of dinosaurs” — Tyrannosaurus rex — had evolved, to feast on many of the herbivores.
Paleontologists still debate what the first ever diet was for all dinosaurs. In other words, they still are not sure whether or not the first dinosaur was an herbivore or a carnivore. It could be that, even though the ancestors of C. diegosuarezi were carnivores, their even earlier ancestors might have been plant eaters.
Today’s dinosaurs, birds, perhaps reflect this mixed-up diet. Many modern birds, like humans, have evolved the ability to process both certain meat, and/or fish, and plant materials.
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