Was meat, plant-based food or both on the menu? A study now sheds light on how the pioneers of the dinosaur era fed around 200 million years ago. Analysis of dental characteristics from early representatives of the main lineages of these animals shows that some of the later herbivores evolved from carnivores and omnivores. Even the ancestors of the long-necked sauropods appear to have been carnivores in the beginning. The ability to modify their diet early in their evolution may have played an important role in the dinosaurs' successful evolutionary trajectory, the paleontologists say.
They dominated terrestrial wildlife for an enormous period of time, until their violent end 66 million years ago: the dinosaurs were an extremely successful group of animals. In their long history of development, they produced many different groups and species, which shaped the Jurassic and Cretaceous periods in particular. Through many shapes, sizes and diets, they have been able to conquer numerous ecological niches in the world. But how did that start? According to fossil finds, the first dinosaurs appeared around 235 million years ago - during the Triassic period. These early representatives already possessed basic characteristics characteristic of their family, but appeared even more humble than many of the later dinosaurs. Because at the beginning of their evolutionary history, they were literally overshadowed by the crocodile-like reptiles that dominated the Triassic period.
Diet in the mirror of tooth characteristics
However, certain traits appear to have allowed dinosaurs to survive the Triassic-Jurassic boundary mass extinction event and subsequently flourish to become the dominant group for the remainder of the Mesozoic. Their adaptability to different diets may have played a role in this. "Soon after their emergence, dinosaurs exhibited an interesting variety of skull and tooth shapes. This has long led paleontologists to suspect that different species were already experimenting with different diets," says lead author Antonio Ballell of the University of Bristol.
Conclusions were already drawn based on the tooth characteristics, but questions remained unanswered. That's why Ballell and his colleagues have now taken this detection approach to a new level. Among other things, a form of artificial intelligence was used. "We used a number of new computational methods to capture the shape and function of early dinosaur teeth and compare them to modern-day reptiles, which have different diets. This included the mathematical modeling of their tooth shapes and the simulation of their mechanical reactions to biting forces using technical software,” explains the scientist.
Flexibility is evident
The scientists used this method in the case of the fossil teeth of dinosaurs, which are considered to be early representatives of important lineages: the theropods, which later included T. rex and Co., the ornithischians such as Tricertatops, and the sauropodomorphs, which eventually produced the long-necked giants . "With our toolkit, we were now able to numerically quantify how similar the characteristics of early dinosaurs were to those of modern animals, providing solid evidence for their diets," says co-author Mike Benton from the University of Bristol. It turns out that early theropod dinosaurs tended to have sharp, curved, and blade-like teeth with tiny prongs that resembled those of modern monitor lizards. They were therefore consistently classified as carnivores. In the case of the early Ornithischia and Sauropodomorpha, on the other hand, a more differentiated picture was reflected in the tooth characteristics.
"Our analyzes suggest that the Ornithischia - the group that includes many herbivorous species such as the horned dinosaurs, armored ankylosaurs and duckbilled dinosaurs - were initially omnivores," says senior author Emily Rayfield of the University of Bristol. In the case of the early Sauropodomorpha, it is becoming apparent that these ancestors of herbivorous long-necked dinosaurs such as Diplodocus were first carnivores and then switched to plants. "During the late Triassic and early Jurassic periods, they began experimenting with different diets," the researchers write. According to them, the later typical purely plant-based diet of the Ornithischia and the Sauropodomorpha was a relatively late evolutionary innovation. "It turns out that early dinosaur diets were quite diverse," Rayfield says.
On the importance of the insights into the diets of the early dinosaurs, Ballell concludes: "It seems that one aspect that made the first dinosaurs special was that they evolved different diets during the Triassic, and we think this is the key to their evolutionary and ecological success," says the paleontologist.
Source: University of Bristol, professional article: Science Advances, doi: 10.1126/sciadv.abq5201