Fossil experts have primed the goose for a key tenet of avian evolution after finding a premodern bird from over 65 million years ago that could move its beak like modern fowl.
The toothy animal was discovered in the 1990s by an amateur fossil collector at a quarry in Belgium and dates to around 66.7 million years ago – shortly before the asteroid strike that wiped out 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 are able to do is [move] our lower jaw. Our upper jaw is totally fused to our skull – it’s completely still,” said Dr Daniel Field, lead author of the University of Cambridge research.
Non-avian dinosaurs, including tyrannosaurs, also had a 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 their lower and upper jaws independently of the rest of the skull and each other.
This, Field says, makes the beak more flexible and dexterous, which helps with preening, building nests and finding food. “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 condition of all modern birds was that merged condition characterized by ostriches and their relatives simply because it looks simpler and more reminiscent of non-bird reptiles,” added Field.
Birds with mobile palates are called neognaths, or “new jaws”, while those with fused palates are paleognaths, or “old jaws”.
The study, which was published in the journal Nature, should ruffle feathers, not only because it suggests the movable palate predates the origin of modern birds, but that the immediate ancestors of ostriches and their relatives have continued to develop a fused palate.
“Why the ancestors of ostriches and their relatives would have lost this beneficial paddle conformation is, at this point, still a mystery to me,” Field said.
The discovery was made when Field and his colleagues examined the fossils using computed tomography techniques. Researchers have found that a bone previously thought to come from the animal’s shoulder actually came from its palate.
The team tagged the newly discovered animal Janavis finalidens in reference to the Roman god who looked both backward and forward, and a nod to the animal’s place in the bird family tree. The portmanteau of Latin words for “final” and “teeth” reflects the existence of Janavis shortly before the toothed birds were wiped out in the ensuing mass extinction.
The site of its discovery means it lived around the same time and place as the toothless “wonderchicken”, the oldest known modern bird, albeit at 1.5 kg (3.3 lb), Janavis would have weighed almost four times as much.
Although the bones from wonderchicken’s palace were not preserved, Field said he was confident they would have been similar to those of Janavis. However, he added that the difference in size of the creatures could explain why wonderchicken’s parents survived the disaster 66 million years ago, but those of Janavis not.
“We think this mass extinction event was very selective in terms of size,” he said. “Large-bodied animals in terrestrial environments resisted this mass extinction event terribly.”
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 family tree of birds from three unusual and extinct groups that lived after the mass extinction, including Dromornithidae, known as demon ducks and Gastornithidae, considered a type of giant flightless fowl.
“If this feature of the palate is primitive, I see that [these groups] could have had older origins and possibly survived from the Cretaceous,” he said.
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