Nature magazine reports that the Aurornis xui specimen was technically discovered by a Chinese farmer several years ago. But it had remained unidentified until paleontologist Pascal Godefroit stumbled across the fossil last year in the museum at the Fossil and Geology Park in Yizhou.
“In my opinion, it's a bird,” Godefroit, who is at the Royal Belgian Institute of Natural Sciences in Brussels, told Nature. “But these sorts of hypotheses are very controversial. We’re at the origins of a group. The differences between birds and [nonavian] dinosaurs are very thin.”
Godefroit and his team of researchers have written a paper on the Aurornis xui that was published in the latest issue of Nature, where it is described as the "most primitive" bird specimen yet discovered.
So, why is there a debate on whether the specimen should be considered the world’s first bird?
First of all, the Aurornis xui, aka Aurora, most likely didn’t actually fly. Instead, it’s believed its four wings were used to help it glide through forests during the late Jurassic period about 150 million to 160 million years ago.
Luis Chiappe, director of the Dinosaur Institute at the Natural History Museum of Los Angeles in California, told Nature that he believes the Archaeopteryx is still the first known “bird” in history, describing Aurora as “something that’s very close to the origin of birds, but it’s not a bird.”
In addition, Paul Barrett of the Natural History Museum of London said for now it’s impractical to distinguish which of the two species were in fact birds.
"There's such a gradation in features between them that it's very difficult to tell them apart,” Barrett told Science News. Aurornis xui "is certainly an older member of the bird lineage than Archaeopteryx, and it's fair to call it a very primitive bird. But what you call a bird comes down to what you call a bird, and a lot of definitions depend on Archaeopteryx."
Nonetheless, Godefroit said the Aurora has hip bones that strongly resemble modern birds. And because the feather fossils are not well preserved, researchers cannot say for certain that the 3-foot-long Aurora was a glider rather than a full-fledged flier.
Its length puts it at about the same size as other modern-day pheasants. However, the Aurora is described as having razor-sharp teeth, claws and a long tail that make it sound far more formidable than your average bird.
In April 2012, the remains of a giant feathered dinosaur were discovered in China, marking it as the oldest known feathered dinosaur in history. It was estimated to have lived about 10 million years after Aurora.
In addition, Godefroit says Archaeopteryx is more closely related to nonavian dinosaurs, meaning that birds would have needed to experience two separate forms of evolution to become the flying creatures they are today.
Interestingly, the answer to the debate might lie in the same museum where Aurora was discovered. Godefroit says hundreds of unclassified fossils remain there and at other nearby institutions.
“The biodiversity of these small, birdlike dinosaurs was incredible,” he said.