Small Dinosaur Had Parrot-Like Jaws for Eating Fruit, Fossils Reveal

Fossils from Montana show that the small oviraptorosaur Infernogalus jamesi had jaws that slid back and forth—an unusual feeding adaptation shared with fruit-eating parrots.

A toothless dinosaur with unusual jaws

Infernogalus jamesi lived in what is now the United States during the Late Cretaceous Period, between 68 and 66 million years ago.

The species belongs to Caenagnathidae, a group of toothless, feathered oviraptorosaurs whose diets have long puzzled paleontologists.

“Caenagnathids are a group of oviraptorosaurids primarily found in North America, characterized by long, low edentulous jaws that often have complex occlusal ridges and grooves, elongated, sinuous limbs, and a highly pneumatized skeleton,” said Dr. Gregory Funston, a researcher at Stony Brook University, the Royal Ontario Museum, and the University of California, Davis, with his colleagues.

“This combination of features precluded preservation in many Late Cretaceous sedimentary systems in the Western Interior Basin, resulting in a fossil record dominated by fragmentary and isolated bones.”

“Although a partial skeleton is known, there is nothing yet that allows analysis of the adductor muscle structure of the mandible to elucidate its abnormal mandibular function.”

Fossils from Montana reveal a sliding bite

The holotype specimen of Infernogalus jamesi—a nearly fully articulated skull with partial skeletons—was collected in 2011 from the Hell Creek Formation in Montana.

Additional fossils from Montana, South Dakota, and North Dakota were also assigned to the species.

Bone sections revealed that the animal was at least 6 years old and fully grown, despite weighing an estimated 12 kg.

Using CT scans, the researchers reconstructed the dinosaur’s jaw muscles. Their analysis found that the jaws moved primarily backward and forward rather than up and down, indicating relatively weak bite forces.

The temporomandibular joint appears to have allowed the lower jaw to slide back and forth by up to approximately 15 mm. Ridges and grooves on the upper and lower jaws fit together as the jaws moved.

Did this dinosaur eat fruit?

The researchers found no bezoars inside the specimen’s body cavity. Many herbivorous dinosaurs used these stones to help grind food.

The absence of bezoars, combined with the dinosaur’s relatively weak bite, suggests that Infernogalus jamesi consumed soft foods that still required extensive processing rather than hard, fibrous plants.

The closest comparison among living animals was the Pesquet’s parrot (Psittrichas fulgidus), which eats fruit by grinding the pulp and discarding the seeds.

The authors suggest that Infernogalus jamesi and other caenagnathid oviraptorosaurs may have processed fruit in a similar way.

Fruit-eating adaptations evolved alongside flowering plants

The researchers’ evolutionary analysis suggests that Caenagnathidae arose shortly after the emergence of fleshy fruits, approximately 100 million years ago.

The most specialized members of the group appeared around the same time that fruits became larger and more diverse.

“The herbivorous diet of caenagnathids likely consisted mostly of fleshy angiosperm fruits, which increased in size and diversity with the oviraptorosaur radiation,” the paleontologists said.

“Thus, caenagnathids are one of the strongest candidates for angiosperm-based dietary adaptations in dinosaurs, but their role in the late Cretaceous fruit proliferation that formed the early Cenozoic flora remains unclear.”

The findings are described in a paper published in Nature Communications.

Read the research paper.

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G. F. Funston et al. Fruit-eating adaptation of Late Cretaceous oviraptorosaurs (theropods). Nature Communications, published online October 10, 2026. doi: 10.1038/s41467-026-78343-w.