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CT Scans of Toothed Bird Fossils Lead to Startling Discovery | Fossils

CT Scans of Toothed Bird Fossils Lead to Startling Discovery | Fossils

Fossil experts have pegged the goose as a key tenet in bird evolution after finding a pre-modern bird from more than 65 million years ago that could move its beak like a modern bird.

The toothy animal was discovered in the 1990s by an amateur fossil collector in a quarry in Belgium and dates to about 66.7 million years ago – just before asteroid impact which wiped out the non-avian dinosaurs.

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

“If you imagine how we open our mouths, the only thing we can do is [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 palates, 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, can move both the lower and upper jaw independently of the rest of the skull and of each other.

This, Field says, makes the beak more flexible and dexterous, helping with cleaning, nest building and foraging. “It’s a really important innovation in the evolutionary history of birds. But it was always thought 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 typified by ostriches and their relatives simply because it looks simpler and more closely resembles non-avian reptiles,” Field added.

Birds with movable palates are called neognaths, or “new jaws,” while those with fused palates are paleognaths, or “old jaws.”

study, which was published in the journal Natureit is expected to ruffle feathers, not only because it suggests that a movable palate predates modern birds, but also that the immediate ancestors of ostriches and their relatives evolved a fused palate.

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

The discovery was made when Field and his colleagues examined the fossils using CT scanning techniques. Researchers discovered that a bone previously thought to be from the animal’s shoulder was actually from its palate.

Palace of Janavis finalidens compared to pheasant and ostrich. Photo: Dr Juan Benito and Daniel Field, University of Cambridge

The team tagged the newly discovered animal Janavis finalidens in relation to the Roman god who looked both backwards and forwards, and a nod to the animal’s place on the bird family tree. A portmanteau of the Latin words for “final” and “teeth” reflects existence Janavis not long before the toothed birds were wiped out in the mass extinction that followed.

The location of its discovery means that it lived around the same time and place as Toothless “wonderchicken”, the oldest known modern birdalthough it is 1.5 kg (3.3 lb), Janavis it would weigh almost four times as much.

Although the palate bones of the miracle chicken have not been preserved, Field said he is confident they would have been similar to those of Janavis. However, he added that the difference in the size of the creatures could explain why the miraculous chicken’s relatives survived the disaster 66 million years ago, but Janavis it is not.

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

Professor Mike Benton, a paleontologist at the University of Bristol who was not part of the research, said the study raised questions about the position on the bird family tree of three unusual, extinct groups that lived after the mass extinction, including the Dromornithidae, known as demon ducks, and the Gastornithidae. which are thought to be a type of giant flightless bird.

“If this feature of the palate is primitive, I can see it [these groups] could have an earlier origin and perhaps survive from the Cretaceous onwards,” he said.



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