The earliest dinosaurs included carnivorous, omnivorous and herbivorous species, according to a team of paleobiologists at the University of Bristol.
By studying the shape of the earliest dinosaurs' teeth and modeling their function using computer simulations, experts were able to compare them with living reptiles and their diets.
Their findings, published in the journal Science Advances, show that many groups of herbivorous dinosaurs were originally omnivores and that the ancestors of our famous long-necked herbivores, such as Diplodocus, ate meat. This ability to diversify their diet early in evolution probably explained their evolutionary and ecological success.
"Teeth can give good clues about what an animal eats because they are our tools to break down food," said Antonio Ballell Mayoral, the study's lead author and a senior research associate in the School of Earth Sciences at the University of Bristol. "As such, it's expected that different tooth shapes will be efficient at processing different kinds of food items."
The research team studied the shaping and functioning of the dinosaurs' teeth and made computer models of how stress would be distributed among the teeth when biting. The results were then processed through machine-learning algorithms based on the dental features and diets of 47 living reptiles, the report added.
Researchers suggested that early dietary diversity of dinosaurs played a key role in their rise and later dominance. It allowed them to adapt to changing climates and food resources.
"This study is the first one to demonstrate with modern statistical methods that early dinosaurs explored different kinds of diets and were ecologically diverse," said Ballell. "Our research supports that two of the three main dinosaur lineages, which adapted to a diet of plants, did not start off as herbivores."