66 million years ago, a small dinosaur could probably feed on fruit by using its jaws like a parrot.
Dinosaurs were not limited to large hunters armed with teeth. Some had beaks and mainly ate plants. This was the case with an animal recently described from fossils found in the Hell Creek Formation, in North America, near the end of the age of the dinosaurs.
Reconstruction of Infernogallus jamesi, a small beaked dinosaur that lived at the end of the Cretaceous.
Illustration: Connor Ashbridge, CC BY 4.0, Wikimedia Commons.
Researchers named it Infernogallus jamesi. This bird-like dinosaur weighed about 12 kg, roughly the weight of a small dog. It belonged to a family of beaked dinosaurs related to the ancestors of modern birds. Its nearly complete skull made it possible to understand how its mouth worked.
The most surprising detail is not visible only in the beak. The bones of its skull show that the muscles responsible for closing the jaw were arranged in an unusual way. They may have allowed forward and backward movements, rather than simply opening and closing the mouth.
A comparable mechanism can be found in some fruit-eating parrots. These birds can manipulate and crush their food between the parts of their beak. In Infernogallus, opposing ridges in the jaws may have helped grind food before it was swallowed.
This resemblance interests paleontologists because flowering plants diversified greatly during the Cretaceous. Their fruits also became more varied. This small dinosaur may therefore have benefited from a food resource that was taking up an increasingly important place in the landscape.
The study does not, however, demonstrate that it ate fruit exclusively. No fossilized meal was found in its stomach. The conclusions are based on the shape of the skull and on how the muscles may have worked. They mainly indicate an animal well adapted to a plant-based diet, probably rich in fleshy fruits.
For the researchers, this discovery adds a new piece to the history of relationships between plants and animals. Fruits did not feed only the ancestors of birds or mammals: some non-avian dinosaurs may already have developed ways to exploit them effectively.
Future fossils will help determine whether other closely related species had the same adaptations. Paleontologists are particularly seeking to establish when this way of eating appeared, and whether it evolved in parallel with the growing abundance of fruit.