Fossil experts have uncovered a key principle in bird evolution after finding a pre-modern bird from more than 65 million years ago that could move its beak like modern birds.
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, shortly before the asteroid strike that wiped out the non-avian dinosaurs.
While the fossil was first described in a study some 20 years ago, researchers who re-examined the specimen say they made an unexpected discovery: The animal had a mobile palate.
“If you imagine how we open our mouths, the only thing we are capable of doing is [move] our lower jaw Our upper jaw is totally fused with our skull, it is completely immobile,” said Dr. Daniel Field, lead author of the research from the University of Cambridge.
Non-avian dinosaurs, including tyrannosaurs, also had a fused palate, as did a small number of modern birds, such as ostriches and cassowaries. By contrast, the vast majority of modern birds, including chickens, ducks, and parrots, can move both the lower and upper jaws independently of and from the rest of the skull.
That, Field says, makes the bill more flexible and dexterous, which helps with grooming, nest building and finding food. “That’s a really important innovation in the evolutionary history of birds. But it was always thought of as a relatively recent innovation,” she said.
“The assumption has always been … that the ancestral condition of all modern birds was this fused condition typified by ostriches and their relatives just because it seems simpler and more reminiscent of non-bird reptiles,” Field added.
Birds with a mobile palate are called neognaths, or “new jaws,” while those with a fused palate are paleognaths, or “old jaws.”
The study, which was published in the journal Natureit is expected to ruffle the feathers, suggesting not only that the mobile palate predates the origin of modern birds, but that the immediate ancestors of ostriches and their relatives developed a fused palate.
“Why the ancestors of ostriches and their relatives would have lost that beneficial blade 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. The researchers discovered that a bone previously thought to be from the animal’s shoulder was actually from its palate.
The team has tagged the newly discovered animal Janavis Finalidens in reference to the Roman god looking both backwards and forwards, and a nod to the animal’s place in the bird family tree. The portmanteau of the Latin words for “end” and “teeth” reflect the existence of Janavis shortly before the toothed birds were wiped out in the ensuing mass extinction.
The site of his discovery means that he lived at the same time and place as the toothless.Wonderchicken”, the oldest known modern birdalthough at 1.5 kg (3.3 lb), Janavis it would have weighed nearly four times as much.
While the Wonderchicken’s palate bones have not been 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 relatives survived the catastrophe 66 million years ago, but those of Janavis Nope
“We think this mass extinction event was highly selective in size,” he said. “Large-bodied animals in terrestrial environments did terribly well during this mass extinction event.”
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 in the bird family tree of three unusual and extinct groups that lived after the mass extinction, including the Dromornithidae, known as demons. ducks and Gastornithidae, which is believed to be a type of giant flightless bird.
“If this characteristic of the palate is primitive, I see that [these groups] it could have had earlier origins and perhaps survived from the Cretaceous onwards,” he said.
