Turkey-Sized 'Hell Chicken' Dinosaur Ate Fruit, Jaw Scans Suggest

A newly described dinosaur nicknamed the hell chicken appears to have been among the first known dinosaurs specialized for eating fruit, according to a study in Nature Communications. Called Infernogallus jamesi, it was roughly turkey-sized, weighing around 12 kilograms (26 pounds), and lived alongside Tyrannosaurus rex and Triceratops, ScienceAlert reported.

Researchers from the U.S. and Canada formally named the animal based on five specimens. Its skull and jaw muscles point to a diet of soft food rather than tough plants, nuts or seeds.

What the skull reveals about its diet

Infernogallus had a curved beak, similar to that of a modern parrot or turtle. But the researchers found its bite force was much weaker than in comparable animals, so it was unlikely to have cracked hard nuts, seeds or shells.

It also seems not to have eaten fibrous plants such as ferns, as some plant-eating dinosaurs did. It lacked teeth suited to grinding such material, and the most complete specimen showed no sign of gizzard stones in its gut, according to the report.

CT scans showed that the jaw muscles ran front to back rather than up and down. That means the jaws probably moved forward and backward during chewing. ScienceAlert noted that this arrangement is relatively rare, found mostly in animals with complex jaws, such as humans and parrots that eat almost only fruit.

The palate offered another clue. Instead of teeth, the dinosaur had a pair of bony surfaces with ridges and grooves. The authors wrote that these textured surfaces would have worked like a mortar and pestle on soft food.

Based on these features and the similarities to living parrots, the team hypothesizes that Infernogallus favored drupes, fruits such as peaches and cherries that have one large seed surrounded by soft flesh. That is an inference from anatomy, not a direct observation of what the animal ate.

Thomas Dudgeon, an evolutionary biologist at the Royal Ontario Museum in Canada, said the anatomy is “bizarre among dinosaurs,” and that the team quickly realized it had found something special.

A timing match between fruit and dinosaurs

Infernogallus belongs to a family called caenagnathids. The team traced the family's origin to around 107 to 118 million years ago. Based on earlier data, the first drupes appeared toward the older end of that range.

Early caenagnathids, such as Microvenator, began developing features that could have helped them exploit fruit. By the time Infernogallus appeared, around 68 to 66 million years ago, it was fully equipped for the diet. The researchers described a lock-step pattern between caenagnathid adaptations and the diversification and growth in size of fruiting flowering plants. They said this is consistent with fruit being a significant part of the family's diet.

Why a specialized diet may have been a risk

Infernogallus had several traits associated with the bird lineage that survived the asteroid impact that killed off the non-avian dinosaurs: small body size, a probable bird-like metabolism and a plant-based diet.

The authors speculate, however, that its specialization may have worked against it. Their analyses suggest it relied largely on sporadic or seasonal foods, such as fruit flesh, rather than lasting ones, such as the seeds inside. Earlier work suggests that access to lasting food sources was likely a key factor in survival when the base of land food webs collapsed at the end of the Cretaceous. This part of the study is presented as speculation.

Why it matters

The finding does not change anything in daily life, but it adds detail to the picture of what dinosaurs ate and how they lived. It suggests that fruit eating, which is rare among animals, evolved in a dinosaur family tens of millions of years before the extinction, and that it tracked the rise of fruiting plants. It also shows how a narrow diet can bring both success and vulnerability, a question the authors raise for this species while stressing the uncertainty.

What researchers want to study next

The team said future work could examine whether these dinosaurs helped spread plant seeds by eating fruit, as modern fruit eaters do. For now, that question remains open.

Read next
115-Million-Year-Old Dinosaur Bone From Brazil Holds Traces of Blood Molecules
Possible Red Blood Cells Found in a 115 Million-Year-Old Dinosaur Bone
Armored Amphibian Fossils From China Suggest a Creature That Never Left the Sea

Around Prague, based on reporting by ScienceAlert