A small, toothless dinosaur with a parrot-like head may be the earliest known dinosaur to specialize in eating fruit, according to a study published in Nature Communications. Named Infernogallus jamesi, it lived about 66 million years ago and was roughly the size of a turkey.

Fossils found in Montana and North Dakota indicate that the animal was about 1.5 metres long and weighed around 10 kilograms. Its beak and jaws were adapted to crush soft foods, including fruit. The remains include a nearly complete skeleton and separate jaw and palate bones, but no feathers were preserved. Researchers infer that it was feathered based on fossils of related animals.

The species’ name means “hell chicken,” referring both to its bird-like appearance and to the Hell Creek rock formation where its fossils were discovered. The formation, which extends across Montana, North Dakota, South Dakota and Wyoming, has yielded remains of several well-known dinosaurs. Infernogallus shared its habitat with animals including Tyrannosaurus, Triceratops and Ankylosaurus.

Researchers point to three features that support a fruit-based diet: jaw muscles that enabled forward-and-back chewing, a movable joint that let the lower jaw slide forward, and ridges and grooves on the beak that helped cut and grind soft plants. Paleontologist Greg Funston of Stony Brook University, the study’s lead researcher, said the combination indicates a high degree of dietary specialization.

Infernogallus belonged to the theropod group, which includes Tyrannosaurus rex, other meat-eating dinosaurs and the lineage leading to birds. Most plant-eating theropods swallowed stones, known as gastroliths, to help grind food. Infernogallus and other members of a group called caenagnathids instead chewed their food.

The fruits available to the dinosaur may have included berries and drupes, a category that today includes fruits with a central stone, such as peaches and cherries. Co-author Thomas Dudgeon, a postdoctoral researcher at the Royal Ontario Museum, said fruit-eating had previously been suggested for some dinosaur groups, but evidence had been lacking.

Fruit-eating animals can help flowering plants spread by dispersing their seeds. Funston said caenagnathids may have played that role, but added that more evidence is needed to establish the connection with confidence.

Sources: Folha Ciência.