Dinosaurs are divided into two groups, Saurischians and Ornithischians, based on their pelvic structure. Saurischians included carnivorous theropods and herbivorous sauropodomorphs, while Ornithischians included various herbivores. Both groups evolved around 230-225 million years ago and only became prominent after the Permian-Triassic extinction event. All non-avian dinosaurs went extinct 65 million years ago, leaving no living […]