Lots of dinosaurs had feathers. But only a handful developed those feathers to fly. In fact, determining which feathered dinosaurs flew and which did not has historically posed a problem for paleontologists. However, a new study suggests that the problem is not as complicated as previously thought.
In the study, published in PNAS, a pair of paleontologists exhibit a variety of traits that, they say, all feathers are built to share flight. Based on the feathers of the dinosaurs’ only surviving descendants, birds, these traits could shed light on which dinosaurs developed the ability to fly and when.
“Theropod dinosaurs, including birds, are one of the most successful vertebrate lineages on our planet,” said Jingmai O’Connor, one of the study’s authors and a paleontologist at the Field Museum in Chicago, in a Press release. “One of the reasons they are so successful is their flight. One of the other reasons is probably their feathers, because they are very versatile structures. “Therefore, any information that can help us understand how these two important characteristics co-evolved (…) is really important.”
Feathers, flight and becoming birds
Not all dinosaurs developed feathers and not all developed flight, but some dinosaurs in the theropod family did. both. Although most of the family, including the tyrannosaurs and the velociraptors, Bursting into feathers with their feet firmly planted, a small subset of theropods evolved feathers that took them to the skies some 230 million years ago. (It was among these feathered flying beasts that the first birds became birds.)
Of course, paleontologists can’t just look out the windows to see which ancient dinosaurs evolved feathers for flight. Instead, they typically look to theropod fossils for clues (including the size and shape of arm bones, wings, and forks) to determine which feathered dinosaurs were also flying dinosaurs.
In the recent study, O’Connor and Yosef Kiat, another paleontologist at the Field Museum in Chicago, focused on the structure of the feathers of birds, the only surviving descendants of dinosaurs and the only surviving theropods in the world today. By investigating the distribution of their feathers and other feathery features, the pair found several traits that all flying birds seem to share.
According to the team, these traits date back to the ancient ancestors of birds (appearing in the fossilized feathers of flying theropods) and therefore function as an indicator of which feathered dinosaurs flew and which did not.
Read more: Did all dinosaurs have feathers?
What is the difference between flying and flightless feathers?
To reach their conclusions, the team studied the feathers of more than 340 species of flying and flightless birds, from pelicans to penguins. By comparing and contrasting the feathers of fliers with those of non-fliers, the team identified several traits shared among bird species that take to the skies.
For example, according to paleontologists, the primary feathers along the tips of a bird’s wings are always asymmetrical in flying birds and symmetrical in flightless ones. And, in addition to feather distribution, the pair discovered that the number of primary feathers in flying birds is always between 9 and 11, while the number of primary feathers in flightless birds is all over the place, between 0 and 11. Over 40.
“They all share the trait of having between 9 and 11 primary feathers,” Kiat said in a press release. “I was surprised that no one seemed to have found this before.”
Why are flying and flightless feathers so important?
Testing their findings further, O’Connor and Kiat identified the flight abilities of 35 different species of fossil theropods, thanks to their shared set of feather traits.
“Basically, you can look at the overlap of the number of primary feathers and the shape of those feathers to determine whether a fossil bird could fly and whether its ancestors could,” O’Connor said in a news release.
Evaluation of fossil theropods Archeopteryx and microraptorFor example, they found that both had between 9 and 11 primary feathers, asymmetrical and suitable for flight. Alternatively, they found that Caudipteryx It had 9 primary feathers in a symmetrical arrangement, suggesting that the theropod remained terrestrial.
According to the team, the findings could solve some of the biggest mysteries about dinosaur feathers and flight. “There have been debates about whether flight evolved in dinosaurs just once or several different times,” O’Connor said in a news release. “Our results here seem to suggest that flight only evolved once in dinosaurs, but we have to really recognize that our understanding of flight in dinosaurs is just beginning.”
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