All dinosaurs in the game must defend themselves from predators, especially herbivores. That could mean running over the predator. Imagine for example a T.rex attacking a herd of Triceratops, the herd runs and one of the herbivores runs over and tramples the T.rex with its powerful horns. Parasaurolophus and Edmontosaurus must have the power to trample small and medium predators while running. Thus, hunting attempts would be more realistic, involving chances of success and failure and in a given case, the carnivore (large/medium/small) can be killed or go away injured in some situations.