Fossils from Montana show a small oviraptorosaur with a jaw that slid front to back, a feature shared with fruit-eating parrots.
Infernogallus jamesi, a small oviraptorosaur that roamed our planet near the end of the Cretaceous period, may have fed on fleshy fruit. Image credit: Funston et al., 10.1038/s41467-026-78343-w.
Infernogallus jamesi lived in what is now the United States during the latest Cretaceous, 68 to 66 million years ago.
The species belongs to Caenagnathidae, a group of toothless, feathered oviraptorosaurs whose diets have long puzzled paleontologists.
“Caenagnathids were a predominantly North American group of oviraptorosaurs distinguished by long, low edentulous mandibles that often bear complex ridges and grooves on their occlusal surfaces; elongate, gracile limbs; and highly pneumatized skeletons,” said Dr. Gregory Funston, a researcher at Stony Brook University, the Royal Ontario Museum and the University of California, Davis, and his colleagues.
“This combination of features selects against their preservation in many Late Cretaceous depositional systems in the Western Interior Basin, resulting in a fossil record dominated by fragmentary, isolated bones.”
“Although partial skeletons are known, none have yet enabled analysis of the mandibular adductor musculature, which would elucidate the functions of their unusual mandibles.”
The holotype specimen of Infernogallus jamesi — a nearly complete, articulated skull with part of the skeleton — was collected in 2011 from the Hell Creek Formation in Montana.
Additional material from Montana, South Dakota and North Dakota was also assigned to the species.
Bone sections showed the animal was at least 6 years old and fully grown, despite weighing an estimated 12 kg (26 pounds).
Using CT scans, the researchers reconstructed the jaw muscles and found that they pulled mostly front to back rather than up and down, which suggests a weak bite.
The jaw joint appears to have let the lower jaw slide forward and backward by up to about 15 mm.
The upper and lower jaws carried ridges and grooves that would have fit together as the jaw moved.
No stomach stones, which many plant-eating dinosaurs used to grind food, turned up in the specimen’s body cavity.
Together with the weak bite, this points to a diet of soft food that still needed a lot of processing, rather than tough, fibrous plants.
Among living animals, the closest match was the Pesquet’s parrot (Psittrichas fulgidus), a bird species that eats fruit by mashing the pulp and discarding the seeds.
The authors propose that Infernogallus jamesi and other caenagnathid oviraptorosaurs may have eaten fruit in a similar way.
Their evolutionary analyses suggest caenagnathids arose roughly 100 million years ago or more, soon after fleshy fruits appeared.
The most specialized members of the group emerged around the time fruits grew larger and more varied.
“Caenagnathids’ herbivorous diet likely consisted in large part of fleshy angiosperm fruits, which increased in size and diversity in concert with the radiation of oviraptorosaurs,” the paleontologists said.
“Caenagnathids thus provide one of the strongest candidates for angiosperm-based diet adaptations in dinosaurs, but their role in the Late Cretaceous proliferation of fruit — which shaped early Cenozoic flora — remains unclear.”
Infernogallus jamesi is described in a paper published this month in the journal Nature Communications.
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G.F. Funston et al. Fruit-eating adaptations in a Late Cretaceous oviraptorosaur (Theropoda). Nat Commun, published online October 10, 2026; doi: 10.1038/s41467-026-78343-w
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