Meet Infernogallus jamesi: the 'hell chicken' that may be the first fruit-eating dinosaur

Sixty-six million years ago, while Tyrannosaurus rex and Triceratops roamed a subtropical floodplain, a feathered, turkey-sized creature with a parrot-like beak was quietly munching on fruit. Scientists have now formally described that creature — Infernogallus jamesi, the 'hell chicken' — and argue it represents the first known dinosaur specialized for eating fruit.

The fossil, discovered in the Hell Creek Formation in July 2011, is remarkable for what it preserved: nearly the entire skeleton, minus the tail, and crucially, the only intact skull ever found for its family, the Caenagnathidae. Caenagnathid skulls are so delicate that they almost never survive fossilization, leaving scientists guessing for decades about what these animals ate. Infernogallus changes that.

Its skull fits in the palm of your hand. You can clearly see the beak; you can see where the eye used to be. It's astonishing.— Dr Tom Dudgeon, study author

The skull presented its own challenges: the lower jaw bones had been crushed. Gregory F. Funston at Stony Brook University and colleagues used CT scans to digitally separate and reconstruct individual bones, stitching together three overlapping scans because the specimen was slightly larger than the scanner's field of view. The effort revealed details of the palate invisible from the surface — details that proved decisive.

It was tougher than usual to work with the CT scans because although the specimen is pretty complete, it's so fragile that every little crack showed up in the scans. But it was worth it – we got details of the palate that we couldn't see from the surface, and they're what helped us interpret the unusual jaw musculature of Infernogallus.— Dr Greg Funston, Stony Brook University, study author

What those details showed was a jaw built for a very different purpose than tearing or crushing. Rather than a strong up-and-down bite, the muscles were arranged to slide the lower jaw backward and forward. The palate arches downward rather than upward as seen in other species. Ridges and grooves inside the mouth appear to have acted like a mortar and pestle to mash soft food, according to the study published in Nature Communications. The fossil beak also bears notches similar to those found on modern fruit-eating species, and its closest resemblance is to fruit-eating parrots and the beaks of herbivorous sea turtles.

We can tell from the skull of Infernogallus, specifically how its muscles are arranged for a front-to-back chewing motion, that it would have been pretty good at chewing its food, which is helpful for fruits with a soft flesh around a central pit (think cherries). We know from the fossil record that these kinds of fruits show up just before caenagnathids evolved, and then they got really big and abundant when caenagnathids were most abundant late in the Cretaceous.— Dr Greg Funston, Stony Brook University, study author

The fruits in question — known as drupes, resembling modern peaches and cherries — were among the first complex fruits produced by the flowering plants that were spreading across Cretaceous landscapes. The researchers argue that oviraptorosaurs, the wider group that includes caenagnathids, diversified in step with those plants, evolving better fruit-chewing abilities roughly when fruits were getting bigger and more complex.

The absence of stomach stones — rocks many plant-eating dinosaurs swallowed to help grind food — in the body cavity further supports a soft-food diet, since an animal processing pulpy fruit would have little use for them, according to phys.org.

There's truly nothing else like Infernogallus, but if I had to pick, I'd say a cassowary with the head of a parrot. If it were alive today, we might struggle to distinguish it from a big flightless bird, because it had a parrot-like head with a toothless beak and big eyes, and would have been covered in feathers. However, when we look at the details of how it chewed its food, it's closest to a specific species called the vulturine parrot, which only eats fruit. Based on these biomechanical similarities, we think Infernogallus likely had a similar diet.— Dr Greg Funston, Stony Brook University, study author

The name Infernogallus combines the Latin for 'hell' — a nod to Hell Creek — with gallus, meaning chicken. The species name jamesi honors James William Boyd, the grandfather of one of the study authors, who sparked his interest in palaeontology, according to IFLScience. The Hell Creek Formation, which stretches across parts of Montana, South Dakota, and North Dakota, is one of the world's richest fossil sites and dates to the very end of the dinosaur era.

Caenagnathids had long puzzled scientists, with proposed diets ranging from eggs and insects to strict plant-eating. Because their skeletons are lightly built and their skulls especially fragile, complete specimens are extraordinarily rare. Infernogallus provides the first intact cranium for the entire family, giving researchers an unprecedented window into how these animals fed.

Open questions remain. Whether Infernogallus and its relatives actively helped spread seeds and shaped early plant evolution is unresolved. 'Their role in the Late Cretaceous proliferation of fruit — which shaped early Cenozoic flora — remains unclear,' the researchers write. What the find does establish is that, at least by 66 million years ago, some dinosaurs had evolved a feeding system sophisticated enough to process the same kinds of fleshy fruits that birds and mammals would later come to depend on.

Why it matters — Infernogallus is the first dinosaur identified as specialized for eating fruit, suggesting that the co-evolution of fruiting plants and fruit-eating animals — a relationship central to modern ecosystems — began tens of millions of years earlier than previously known.

Reported by reuters.com, phys.org, iflscience.com