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A peculiar fossil has helped scientists discover an unusual bird that lived among the dinosaurs 120 million years ago, and the find is changing the way researchers think about bird evolution.
The previously unknown species has been named Imparavis attenboroughi, which means ‘Attenborough’s strange bird’ in Latin, in honor of British naturalist Sir David Attenborough.
All birds are descended from dinosaurs, and some of the earliest birds looked like them. But Imparavis, which belonged to a diverse bird group called enantiornithines, probably looked more like the birds we know today, according to a new study published Tuesday in the journal Cretaceous Research.
Enantiornithines are known as ‘opposite birds’ because they had shoulder joint function very different from that of modern birds.
“Enantiornithines are very strange. Most of them had teeth and still had clawed fingers,” lead study author Alex Clark, a doctoral candidate at the University of Chicago and the Field Museum of Natural History, said in a statement. “If you were to go back in time 120 million years in northeastern China and walk around, you might have seen something that looked like a robin or a cardinal, but then it would open its mouth and it would be filled with teeth, and he would lift his wing, and you would realize he had small fingers.
But according to the study, Imparavis was the first known bird of its kind to be toothless in a landscape full of birds with teeth.
“Before Imparavis, toothlessness was known to have occurred in this group of birds about 70 million years ago,” says Clark. “With Imparavis it turns out that it took place almost 48 million years earlier. Nowadays all birds have no teeth. But in the Mesozoic era, small toothed mouths were the norm. If you saw one without teeth, it would be the odd one out – and that was Imparavis.”
Found a strange fossil
The fossil was first discovered by an amateur collector near Toudaoyingzi village in northeastern China and donated to the Shandong Pingyi Tianyu Nature Museum. When Jingmai O’Connor, the Field Museum’s associate curator of fossil reptiles, visited the Shandong museum’s collections a few years ago, the fossil caught her attention.
“I think what attracted me to the specimen was not the lack of teeth, but the forelimbs,” co-author O’Connor, who is also Clark’s advisor, said in a statement. “It had a giant bicipital crest – a bony protrusion that extended from the top of the upper arm bone, where the muscles attach. I have seen such crests in Late Cretaceous birds, but not like these in the Early Cretaceous. That’s when I first suspected that it might be a new species.”
Clark, O’Connor and their colleagues began studying the fossil in early 2023 and were surprised by the bird’s lack of teeth, in addition to the unusual forelimbs or wing bones.
Imparavis had large attachment points for the muscles in its wing bones, indicating that it could generate a lot of force with its wings and had a strong downward wing beat, kind of like doing a huge air push-up, Clark said.
“We may be looking at very strong wing beats. Some features of the bones resemble those of modern birds, such as puffins or murres, which can flutter insanely fast, or quail and pheasants, which are sturdy little birds but produce enough force to launch almost vertically in an instant if they are threatened,” Clark said.
While modern birds have fused the digits of the forelimbs, enantiornithines still had independent movement in the ‘pinky fingers’ on their wings.
“Most of the ‘hand’ would have been encased in tissue to help form the wing, but the small claws (and yes, they had small claws) could have been used to manipulate food, aid in climbing, or other things not yet thought of. -of behavior,” Clark said.
The mysteries of bird evolution
Clark and his colleagues can’t say for sure what type of food Imparavis ate or exactly why it was toothless. Features of the bird’s hind legs indicate that it probably foraged on the forest floor, perhaps looking for fruit, seeds or insects.
The bird, like other enantiornithines, lacked a digestive organ called a gizzard, which helps modern birds grind their food for easier digestion. “So the evolutionary pressures that led to toothlessness in other groups of dinosaurs were probably not the same for enantiornithines like Imparavis,” Clark said.
As other birds lost their teeth over time, they swallowed stomach stones to create a stomach mill that helped grind the food they ate. But Imparavis didn’t behave like that. Until scientists find more examples of Imparavis, the mystery of what the bird ate and how it digested food remains.
Imparavis could probably be seen jumping and walking on the ground like modern robins, Clark said.
“It appears that most enantiornithines were quite arboreal, but the differences in the structure of the forelimbs of Imparavis suggest that although it was probably still arboreal, it may have ventured to the ground to feed, and that could mean he had a unique diet. compared to other enantiornithines, which could also explain why he lost his teeth,” O’Connor said.
One of the key remaining questions among researchers about bird evolution is why the 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 might be because ornithuromorphs were more commonly associated with water/river systems, others might think they had different metabolisms, and still others might still think about differences in nesting or rearing young,” Clark said in the statement. “This is where more fossil specimens and more statistical modeling will come into play in the future – so stay tuned!”
Understanding extinct species
Clark is currently researching new specimens that show both the surprising similarities and differences between ancient and modern birds, and reveal what “little paradoxical creatures” they may be.
Clark attributes his interest in the natural sciences to watching Attenborough’s nature documentaries, hence the new fossil’s name.
“It is a great honor to attach your name to a fossil, especially one as spectacular and important as this. It appears the history of birds is more complex than we knew,” Attenborough said in a statement.
But studying extinct animals not only sheds light on the past, but also raises awareness for the future, the researchers said.
“Learning about enantiornithines like Imparavis attenboroughi can help us understand why they went extinct and why modern birds have survived, which is very important for understanding the sixth mass extinction we are now in,” says O’Connor. “The greatest crisis facing humanity is the sixth mass extinction, and paleontology provides the only evidence we have for how organisms respond to environmental change and how animals respond to the stress of the extinction of other organisms. ”
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