Fossil named 'Attenborough's strange bird' was the first of its kind without teeth

No birds alive today have teeth. But that wasn't always the case; many early fossil birds had beaks full of sharp, tiny teeth. In a paper in the journal Cretaceous Research, scientists have described a new species of fossil bird that was the first of its kind to evolve toothlessness; its name, in honor of naturalist Sir David Attenborough, means "Attenborough's strange bird."

"It is a great honor to have one's name attached to a fossil, particularly one as spectacular and important as this. It seems the history of birds is more complex than we knew," says Sir David Attenborough.

All birds are dinosaurs, but not all dinosaurs fall into the specialized type of dinosaurs known as birds, sort of like how all squares are rectangles, but not all rectangles are squares. The newly described Imparavis attenboroughi is a bird, and therefore, also a dinosaur.

Imparavis attenboroughi was a member of a group of birds called enantiornithines, or "opposite birds," named for a feature in their shoulder joints that is "opposite" from what's seen in modern birds. Enantiornithines were once the most diverse group of birds, but they went extinct 66 million years ago following the meteor impact that killed most of the dinosaurs. Scientists are still working to figure out why the enantiornithines went extinct and the ornithuromorphs, the group that gave rise to modern birds, survived.

"Enantiornithines are very weird. Most of them had teeth and still had clawed digits. 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 it would raise its wing, and you would realize that it had little fingers," says Alex Clark, a Ph.D. student at the University of Chicago and the Field Museum and the paper's corresponding author.

But "Attenborough's strange bird" bucked this trend.

"Scientists previously thought that the first record of toothlessness in this group was about 72 million years ago, in the late Cretaceous. This little guy, Imparavis, pushes that back by about 48 to 50 million years. So toothlessness, or edentulism, evolved much earlier in this group than we thought," says Clark.

The specimen was found by an amateur fossil collector near the village of Toudaoyingzi in northeastern China and donated to the Shandong Tianyu Museum of Nature. Clark's advisor and co-author on the paper, Field Museum associate curator of fossil reptiles Jingmai O'Connor, first noticed something unusual about this fossil several years ago, when she was visiting the Shandong Tianyu Museum's collections.

"I think what drew me to the specimen wasn't its lack of teeth— it was its forelimbs," says O'Connor. "It had a giant bicipital crest—a bony process jutting out at the top of the upper arm bone, where muscles attach. I'd seen crests like that in Late Cretaceous birds, but not in the Early Cretaceous like this one. That's when I first suspected it might be a new species."

O'Connor, Clark, and their co-authors in China, Xiaoli Wang, Xiangyu Zhang, Xing Wang, Xiaoting Zheng, and Zhonghe Zhou, undertook further study of the specimen and determined that it did indeed represent an animal new to science.

The unusual wing bones could have allowed for muscle attachments that let this bird flap its wings with extra power.