When did birds first emerge from among the dinosaurs? It’s an argument that has plagued paleontologists and cast a shadow over the reputation of Archaeopteryx, a feathered dinosaur that has long been considered the earliest known bird.
Now, scientists say they found an even older feathered dinosaur – one that reestablishes Archaeopteryx as part of the bird lineage even as it may simultaneously dethrone Archaeopteryx as the earliest known "bird." The study, published online in the journal Nature, provides a key link in the evolutionary chain of events that led from dinosaurs to birds.
"It pushes [back] the origins of birds — or origin of animals that are very closely related to the bird," said Luis Chiappe, a vertebrate paleontologist at the Natural History Museum of Los Angeles who was not involved in the paper. "And that’s quite exciting."
But some say the fossil may just represent a bird-like dinosaur, not a true bird — and in any case, could have been altered before scientists had a chance to study it.
The new find, christened Aurornis xui, was discovered in northeastern China in the Liaoning Province. The 20-inch, chicken-sized fossil is estimated to be about 160 million years old, about 10 million years older than Archaeopteryx.
After a thorough examination of the fossil researchers from Europe and China constructed a computer-generated family tree that puts both Aurornis and Archaeopteryx in the Avialae family – the group of dinosaurs whose only living representatives are birds.
"Around the origin of birds 160 million or so years ago, there were many fossils that were experimenting with birdness — getting more and more bird-like," Chiappe said. "What exactly the line is that made it to birds is not entirely clear … and this is just one candidate."
The study authors argue that Aurornis represents the earliest known bird, but other scientists say it could be part of a group of bird-like dinosaurs that were developing feathers and bird-like features but never quite got off the ground, evolutionarily speaking.
"You’re looking at an animal that is either a very primitive bird or something very closely related to birds," Chiappe said. "I tend to think that it’s not a bird, but that it’s one of those true very close ancestors of bird."
In any case, it’s possible the fossil has been altered because it seemed almost too good to be true – too perfectly preserved, Chiappe said. He noted that as many as 80% of fossils in Chinese museums are thought to be artificially "enhanced" in some way.
"I’d like to see the animal at some point," Chiappe said, referring to the fossil.
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