The Proportion of Herbivorous Dinosaurs Compared to Carnivorous Dinosaurs
Palaeontologists can determine what a long, extinct dinosaur ate if cranial material such as jaw bones and teeth are found in association with other skeletal material. Of the twelve hundred or so known species described to date, more plant-eating dinosaurs have been identified than meat-eating ones. It has been suggested that basal members of the Dinosauria were all bipedal, cursorial carnivores and plant-eating was a later adaptation as this group of reptiles diversified. If this is the case, then it suggests that the Saurischian dinosaurs came first with the first Ornithischian members of the Dinosauria evolving later.
Of all the dinosaur discoveries made to date, it has been estimated that around 65 percent of all the specimens represent plant-eating dinosaurs. Some scientists have speculated that if they were able to describe every species of dinosaur that had ever lived, the ratio of plant-eating dinosaurs to meat-eating dinosaurs would actually be higher. A ratio in excess of 70:30 in favour of herbivorous (or semi-herbivorous) has been suggested.