Life reconstruction of the Hell Chicken Infernogallus munching on early fruit, while a T. rex lurks in the background.
© Danielle Dufault, 2025
A dinosaur nicknamed the “hell chicken” might sound like an especially unpleasant predator, but its remarkable skull suggests rather different eating habits. Infernogallus jamesi, a turkey-sized dinosaur from the approximately 66-million-year-old Hell Creek Formation of North America, appears to have specialised in processing soft plant foods, probably including fleshy fruit. Behind the entertaining name lies a useful illustration of evolution: a lineage descended from carnivorous ancestors acquiring a feeding apparatus suited to a very different diet.
The discovery is described in a paper in Nature Communications by Gregory Funston and colleague. Infernogallus belonged to the caenagnathids, a group of toothless, feathered oviraptorosaurs whose feeding habits have been difficult to establish. Its unusually complete skull has now provided evidence that isolated bones could not supply.
Using CT scans and anatomical reconstruction, the researchers investigated how its jaws would have worked. The arrangement of the palate and jaw muscles indicates that the lower jaw could move backwards and forwards, while opposing ridges and grooves helped process food inside the mouth. Rather than an apparatus for tearing flesh, this was suited to mashing softer material. Particularly revealing is the resemblance to feeding adaptations in living fruit-eating parrots: an example of convergent evolution, in which similar functional demands produce comparable adaptations in separate evolutionary lineages.
There is an important distinction here between reconstructing a feeding mechanism and finding the remains of an animal’s last meal. The evidence supports specialised herbivory and makes fleshy fruit a strong candidate, but it does not establish an exclusively fruit-based diet. Nor does it demonstrate that these dinosaurs dispersed seeds or drove the evolution of fruit. The authors identify a potentially significant relationship between dinosaur feeding specialisations and the diversification of flowering plants, while acknowledging that the ecological details remain uncertain.
For creationism, the difficulty extends beyond the familiar problem of a dinosaur living tens of millions of years before the supposed biblical Creation Week. This animal belongs within an evolutionary history of changing anatomy, changing diets and changing ecosystems. Its feeding apparatus was built from the inherited structures of a theropod skull, modified for a new way of obtaining food. Calling it a separately created “kind” supplies neither an explanation for those anatomical relationships nor a testable account of how its specialisations arose.
What makes this discovery especially interesting is the glimpse it offers of an ecological role that has been easy to overlook. The world of the last non-avian dinosaurs contained more than enormous predators and bulk-feeding herbivores. It also supported smaller animals with specialised ways of exploiting plant foods — a diversity that science can reconstruct, cautiously and progressively, from the evidence preserved in their bones.
How can we tell what an extinct dinosaur ate? We cannot watch an extinct dinosaur feeding, but its fossils can preserve several kinds of evidence about its diet. Palaeontologists combine these clues to distinguish what an animal could process, what it probably ate, and, in exceptional cases, what it actually swallowed.The published paper is accompanied by a Royal Ontario Museum news release:
Skulls and jaws: reconstructing the feeding apparatus
The shape of a skull, the surfaces of its teeth or beak, and the position of its jaw joints constrain how an animal could bite and process food. Muscle attachment sites help researchers reconstruct the arrangement and action of muscles that have long since disappeared. CT scans can reveal otherwise inaccessible structures and help scientists reconstruct fragile or distorted fossil bones.
These reconstructions allow researchers to investigate questions such as whether a jaw was suited to forceful biting, slicing, crushing or repeated movements that mashed food. However, a feeding apparatus rarely identifies a single food with certainty: several foods can have similar mechanical properties.
Living animals provide comparisons
Animals whose diets and feeding movements can be observed provide a way to interpret fossil anatomy. If an extinct animal possessed a feeding mechanism resembling that of a living fruit-eater, fruit becomes a plausible dietary candidate. The comparison becomes stronger when several relevant features agree, rather than just the overall appearance of the beak.
This does not mean that the extinct animal necessarily ate exactly the same foods. Similar structures can serve more than one purpose, and living species may vary their diets with season, age or availability.
More direct evidence: meals and droppings
Even a preserved meal is only a snapshot. One animal’s last meal does not establish the complete diet of its species.
- Gut contents: Food remains preserved within an animal’s digestive tract can provide unusually direct evidence of a meal. Such finds are rare, and researchers must distinguish genuine gut contents from material introduced during burial.
- Coprolites: Fossilised faeces may contain fragments of bone, plant tissues, seeds or other dietary remains. These can reveal what was eaten, although identifying the animal that produced a particular coprolite can be difficult.
- Tooth wear: Where teeth are present, patterns of wear can help identify how food was processed and the kinds of material encountered. They do not necessarily identify particular food species.
What does this mean for the “hell chicken”?
In Infernogallus jamesi, the reconstructed jaw musculature and opposing ridges and grooves indicate a mechanism for processing soft food through backwards-and-forwards movements of the lower jaw. Comparisons with fruit-eating parrots support the interpretation that fleshy fruit formed an important part of its diet.
The conclusion is therefore an inference from functional anatomy and comparison with living animals, rather than the identification of fruit in preserved gut contents. It supports probable fruit-eating, but does not establish an exclusively fruit-based diet.
Eating fruit is not the same as dispersing seeds
A fruit-eater might swallow seeds, discard them, or destroy them while feeding. Effective seed dispersal requires seeds to survive and reach places where they can germinate. Evidence that an animal could process fruit therefore does not, by itself, demonstrate that it dispersed seeds or influenced the evolution of fruit-bearing plants.
Recognising these distinctions is part of the strength of palaeontology: researchers can propose a well-supported explanation while identifying which parts remain open to further evidence.
Rare fossil discovery reveals new dinosaur species that were specialized fruit-eaters
Among the ravenous carnivores and lumbering herbivores that roamed the Cretaceous landscape, another kind of dinosaur was evolving that started to eat something else: the plants that began to flower and produce fruit.
The discovery by paleontologists from Stony Brook University, Royal Ontario Museum (ROM), and the North Dakota Geological Survey reveals a new species, Infernogallus jamesi – a type of small oviraptorosaur – had chewing muscles for mashing soft food, making it the first known dinosaur that specifically ate fruit.
Led by Dr. Greg Funston, Assistant Professor in the Department of Anatomical Sciences at Stony Brook University, the research – which analyzed the chewing muscles of the new species, showing that it had a unique arrangement only seen in fruit-eating parrots today – was published in the journal Nature Communications.
We knew dinosaurs evolved to fill so many different roles in ecosystems in the Cretaceous, but we never expected to discover fruit-eating dinosaurs. For more than 100 years, we didn’t know what the skulls of these animals looked like. Now, we know they were even weirder than we could have predicted.
Assistant Professor Dr. Greg Funston, lead author
Department of Anatomical Sciences, Stony Brook University Stony Brook, NY, USA.
Infernogallus, meaning “hell chicken,” was so named because the fossils – including a nearly complete, articulated skull and partial skeleton, currently on display at the Royal Ontario Museum – were found in the Hell Creek Formation in the U.S. (stretching across Montana, North Dakota, South Dakota, and Wyoming), where it would have lived alongside T. rex and Triceratops.
Belonging to a group of toothless, feathered dinosaurs called caenagnathids, Infernogallus was a small dinosaur the size of a turkey, and would have weighed about 12 kg (25 lbs) – making it one of the smallest members of its group even as a fully grown adult.
Curiously, Infernogallus and its relatives evolved from the meat-eating side of the dinosaur tree. Detailed analysis of its chewing mechanics shows that its skull was specialized for mashing stone fruits to remove the flesh from the main seed. This came as a surprise, because paleontologists had previously struggled to show any clear links between dinosaur diversity and the evolution of flowering plants. However, this discovery underscores parallels between the evolutionary radiations of caenagnathids and fruit, with caenagnathids evolving their specialized chewing capabilities as fruits became bigger and more common.
Infernogallus’s ability to chew fruit can be seen in the adaptations to its palatal bones – the parts of the skull that make up the roof of the mouth. Using CT scans to reconstruct the skull, the researchers found that these bones arched downwards into the mouth itself, which made certain muscles face front-to-back instead of up and down. This would have enabled a chewing motion where the beak slid back and forth, like in a human, instead of the rigid vertical bite of T. rex and other dinosaurs.It’s pretty rare for animals to become specialized for a diet of fruit, so when it happens, it comes with some remarkable adaptations. The anatomy of Infernogallus is bizarre among dinosaurs, and we quickly realized that we were dealing with something special.
Dr. Thomas Dudgeon, co-author
Department of Natural History
Royal Ontario Museum
Toronto, ON, Canada.
These forward-facing muscles are rare in the animal kingdom – though are present in mammals like humans who demonstrate complex chewing, and in some birds that specialize in fruit-eating, like the Vulturine Parrot (Psittrichas). The uniqueness of this muscle organization led the researchers to conclude that these adaptations likely evolved for the same reason: processing soft foods – such as fruit – in the mouth instead of the gut.
The revelation that Infernogallus was a fruit-eating dinosaur is additionally significant, as the discovery suggests that dinosaurs may have had an unrecognized impact on the evolution of flowering plants as seed-dispersers – an important role filled by birds, reptiles, and small mammals today. During the Cretaceous period, flowering plants took over from cone-bearing plants as the major vegetation on land – as seen in the fossil record, which includes fossilized fruits.
Complete remains of small dinosaurs like Infernogallus are very rare in the fossil record. The strange skull of Infernogallus is an exciting find because it reveals surprising insights into dinosaur evolution and feeding specialization. This discovery shows that we still have a lot to learn about the world of T. rex, and about dinosaurs more generally.
Professor Dr. David Evans, senior author
Department of Natural History
Royal Ontario Museum
Toronto, ON, Canada.
Recognizing that this species may have played a new ecological role during this period also indicates that we might not yet appreciate the full diversity of dinosaur species and behaviours at the end of the Cretaceous era – adding to the scientific debate about whether dinosaurs were in decline before their extinction.
Publication:
Infernogallus jamesi illustrates how the Theory of Evolution provides a framework for understanding a discovery. Its unusual skull is placed within a family tree, compared with the anatomy of its relatives, and examined for changes in the function of inherited structures. Its probable fruit-processing adaptations make sense as modifications within a theropod lineage whose distant ancestors were carnivorous. The resemblance to fruit-eating parrots supplies a further evolutionary comparison: separate lineages arriving at similar functional solutions.
That framework also allows scientists to investigate a wider ecological question. Could the evolution of specialised fruit-eating dinosaurs have been associated with the increasing availability and diversity of fleshy fruits produced by flowering plants? The researchers identify a possible connection between the diversification of these dinosaurs and that of an increasingly important food resource. This is precisely the sort of relationship evolutionary theory leads scientists to investigate: changes in one group of organisms creating opportunities and potentially altering selection pressures in another.
However, a correlation is not, by itself, proof of a particular causal relationship. Fruit-bearing angiosperms might have provided opportunities that favoured dietary specialisation among dinosaurs, while fruit-eating animals might, in turn, have influenced plants through their feeding behaviour. Demonstrating reciprocal evolutionary change would require further evidence. In particular, the ability to process fruit does not establish that Infernogallus dispersed viable seeds, still less that it drove the evolution of larger or fleshier fruits. The study opens these questions to investigation rather than declaring them settled. Co-evolution does, however, offer a plausible explanation for the rise of fleshy-fruit bearing plants before the evolution of fructivorous birds and mammals. This distinction between an explanatory framework and a predetermined answer is central to science. Evolutionary theory helps researchers formulate questions, compare alternatives and identify evidence that could support or challenge their interpretations. Uncertainty about the precise diet or ecological role of one dinosaur is an invitation to further research. It is not evidence that the evolutionary relationships revealed by its anatomy disappear whenever a detail remains unresolved.
For young-Earth creationism, meanwhile, the chronological problem remains unavoidable: this specialised animal inhabited a complex ecosystem approximately 66 million years ago. For intelligent design, simply attributing its feeding apparatus to a designer adds no testable explanation for its inherited anatomical relationships or its resemblance to independently evolved feeding mechanisms. Science can use those relationships to reconstruct a changing world and investigate how its inhabitants influenced one another. Creationism supplies a conclusion in advance; the fossils supply an evolutionary history.
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