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A strange fossil has helped scientists discover an unusual bird that lived among dinosaurs 120 million years ago, and the find is changing the way researchers think about bird evolution.
The previously unknown species was named Imparavis attenboroughi, Latin for “Attenborough’s strange bird”, in honor of British naturalist Sir David Attenborough.
All birds are descended from dinosaurs, and some of the oldest birds resemble them. But Imparavis, which belongs to a diverse group of birds called enantiornithines, was probably more similar to the birds we’re familiar with today, according to a new study published Tuesday in the journal Cretaceous Research.
Enantiornithines are called “antagonistic birds” because they have a very different shoulder joint feature than today’s birds.
“Enantiornithines are very strange. Many of them had teeth and still had clawed fingers,” said study lead author Alex Clark, a doctoral student at the University of Chicago and the Field Museum of Natural History. “If you were to go back 120 million years in northeast China and walk around, you’d see something that looked like a thrush or a cardinal. “You might have seen it, but then it would open its mouth and it would be full of teeth, and when it lifted its wing, you could tell it had little fingers.”
However, according to the study, Imparavis was the first bird of its kind known to be toothless in a landscape full of toothed birds.
“Before Imparavis, toothlessness in this group of birds was known to have occurred approximately 70 million years ago,” Clark said. “It turns out this happened in Imparavis about 48 million years ago. Not all birds today have teeth. But in the Mesozoic, small-toothed mouths were the norm. It would be weird if you saw one without teeth, and Imparavis was that.”
Finding a strange fossil
The fossil was first discovered by an amateur collector near the village of Toudaoyingzi in northeastern China and donated to the Shandong Pingyi Tianyu Nature Museum. The fossil caught the attention of Jingmai O’Connor, the Field Museum’s assistant curator of reptile fossils, when she visited the Shandong museum’s collections a few years ago.
“I think what attracted me to this specimen was not its lack of teeth, but its front legs,” O’Connor, one of the study’s authors who is also Clark’s consultant, said in a statement. “The upper part of the humerus had a giant bicipital crest, which is a bony process that protrudes where the muscles attach. I’ve seen crests like this in Late Cretaceous birds, but not in Early Cretaceous birds. “That’s when I first suspected this might be a new species.”
Clark, O’Connor and their colleagues began examining the fossil in early 2023 and were surprised by the bird’s lack of teeth as well as its absence. unusual forelimbs or wing bones.
Clark said Imparavis had large attachment points for muscles in its wing bones, indicating that it could generate a lot of power with its wings and had a powerful downward wing stroke, like doing a giant aerial push-up.
“We’re looking at potentially really powerful wing beats. Some of the features of the bones are similar to modern birds like gulls or puffins, which can flap their wings crazy fast, or quails and pheasants, which are large little birds but produce enough force to launch almost vertically in an instant when threatened,” Clark said.
While the forelimbs of modern birds are fused together, the “little fingers” on the wings of enantiornithines could still move independently.
“Most of the ‘hand’ was covered in tissue to help form the wing, but the small claws (and yes, they had small claws) may have been used to handle food, help climb, or other things not yet thought of. -your behavior,” Clark said.
Mysteries of bird evolution
Clark and his colleagues can’t say for sure what kind of food Imparavis ate or exactly why it was toothless. The features of the bird’s hind legs indicate that it foraged on the forest floor, possibly looking for fruit, seeds or insects.
The bird, like other enantiornithines, did not have a digestive organ called a gizzard, which helps modern birds break down their food for easier digestion. enantiornithines like Imparavis,” Clark said.
As other birds lost their teeth over time, they swallowed stomach stones, creating a stomach grinder to help crush the food they ate. But Imparavis did not act this way. Until scientists find more specimens of Imparavis, what the bird eats and how it digests food remains a mystery.
Imparavis could probably be seen hopping and walking on the ground like modern thrushes, Clark said.
“Most enantiornithines appear to be arboreal, but differences in Imparavis’s forelimb structure suggest that although it was probably still living in trees, it may have ventured down to the ground to feed, which may mean it had a unique diet compared to other enantiornithines, which explains why it retained its teeth.” can explain his loss,” O’Connor said.
One of the most important questions remaining among researchers about bird evolution is why more diverse enantiornithines went extinct along with the dinosaurs 66 million years ago, while another group, called ornithuromorphs, survived and allowed modern birds to evolve.
“Some thought this was because ornithoromorphs were more commonly associated with water/river systems, others thought maybe there were different metabolisms, and others thought maybe there were differences in nesting or raising young,” Clark said in the statement. “This is where more fossil samples and more statistical models will come into play in the future, so stay tuned!”
Understanding endangered species
Clark is currently investigating new specimens that show both surprising similarities and differences between ancient and modern birds, revealing what “little paradoxical creatures” they can be.
Clark credits his interest in natural sciences to watching Attenborough’s nature documentaries, hence the name of the new fossil.
“It is a great honor to have your name on a fossil, especially one as magnificent and important as this one. It appears that the history of birds is more complex than we know,” Attenborough said in a statement.
However, according to researchers, studying extinct animals not only sheds light on the past but also increases awareness of the future.
“Learning about enantiornithines like Imparavis attenboroughi helps us understand why they went extinct and why modern birds survived, which is really important for understanding the sixth mass extinction we’re in right now,” O’Connor said. “The greatest crisis facing humanity is the sixth mass extinction, and paleontology provides the only evidence we have of how organisms respond to environmental changes and how animals respond to the stress of other extinct organisms.”
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