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CT scans of toothed bird fossil lead to stunning discovery | fossils

Fossil experts have cooked the goose of a key tenet in bird evolution after finding a premodern bird more than 65 million years ago that could move its beak like a modern fowl.

Discovered by an amateur fossil collector in a quarry in Belgium in the 1990s, the toothy animal dates to around 66.7 million years ago — just before asteroid impact wiped out the non-bird dinosaurs.

While the fossil was first described in a study about 20 years ago, researchers who reexamined the specimen say they made an unexpected discovery: the animal had a movable palate.

“If you imagine us opening our mouths, that’s all we can do [move] our lower jaw. Our upper jaw is completely fused to our skull – it’s completely immobile,” said Dr. Daniel Field, senior author of the study from the University of Cambridge.

Non-avian dinosaurs, including tyrannosaurs, also had fused palate, as did a small number of modern birds such as ostriches and cassowaries. In contrast, the vast majority of modern birds, including chickens, ducks, and parrots, are able to move both their lower and upper jaws independently of the rest of the skull and each other.

That, Field says, makes the beak more flexible and dexterous, aiding in preening, nest-building, and foraging. “This is a really important innovation in the evolutionary history of birds. But it was always assumed to be a relatively recent innovation,” he said.

“The assumption has always been … that the ancestral state for all modern birds was this fused state, typical of ostriches and their kin, simply because it appears simpler and more reminiscent of non-avian reptiles,” Field added.

Birds with a movable palate are called neognathic or “new jaws”, while birds with a fused palate are palaeognathic or “old jaws”.

The study, published in the journal Natureis expected to ruffle feathers, not only because it suggests that the mobile palate predates the origin of modern birds, but that the immediate ancestors of ostriches and their relatives evolved fused palates.

“Why the ancestors of ostriches and their relatives lost this advantageous palette conformation is still a mystery to me at this point,” Field said.

The discovery was made when Field and colleagues examined the fossils using CT scanning techniques. The researchers discovered that a bone thought to have come from the animal’s shoulder actually came from its palate.

Palate of Janavis finalidens compared to that of a pheasant and an ostrich.
palace of Janavis finalidens compared to that of a pheasant and an ostrich. Photo: dr Juan Benito and Daniel Field, University of Cambridge

The team labeled the newly discovered animal Janavis finalidens in an allusion to the Roman god who looked both backwards and forwards, and an allusion to the animal’s place in the bird family tree. The portmanteau of the Latin words for “end” and “teeth” reflects the existence of Janavis just before toothed birds were wiped out in the subsequent mass extinction.

The place of its discovery means that it lived around the same time and place as the Toothless”Wonderchicken”, the oldest known modern birdalthough at 1.5 kg (3.3 lb), Janavis would have weighed almost four times as much.

While Wonderchicken’s palate bones have not survived, Field said he was confident they would have been similar to Wonderchicken’s Janavis. However, he added that the difference in size between the creatures could explain why Wonderchicken’s relatives survived the 66 million-year-old cataclysm, but those of Janavis Not.

“We think this mass extinction was very size selective,” he said. “Large-bodied animals in terrestrial environments have weathered this mass extinction terribly.”

Prof Mike Benton, a University of Bristol paleontologist who was not involved in the research, said the study raises questions about the position of three unusual extinct groups in the family tree of birds that lived after the extinction, including Dromornithidae as demon ducks and Gastornithidae, believed to be a species of giant flightless fowl.

“If that palate feature is primitive, I can see that [these groups] may have had earlier origins and perhaps survived from the Cretaceous,” he said.

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