A new dinosaur fossil unearthed in China chips away at the long-held theory… (Chinese Academy of Sciences )
The famous winged and feathered fossil Archaeopteryx has been knocked off its perch as the oldest known bird, according to new research. Instead, it was most likely a dinosaur.
Archaeopteryx, discovered in Germany in 1861, lived during the late Jurassic period — about 150 million years ago. On the basis of its part-bird, part-reptile features, paleontologists placed it in the avialan family, which includes the earliest ancestors of birds. Avialans are related to deinonychosaurs, bird-like dinosaurs such as Anchiornis and Microraptor that lived during the late Jurassic and subsequent Cretaceous.
The new report, authored by Xing Xu, a paleontologist at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, and colleagues, described the anatomy of a newly found fossil dubbed Xiaotingia zhengi, a two-pound creature with feathers, sharp claws, fewer than 10 teeth and a small shallow snout like Archaeopteryx. It may have lived in northeastern China's Liaoning province during the late Jurassic period, the authors reported online Wednesday in the journal Nature.
The paleontologists then built a family tree by comparing anatomical features of Archaeopteryx, Xiaotingia, other avialans and deinonychosaurs. They noted that the skulls of Archaeopteryx and Xiaotingia were far more similar to those of deinonychosaurs than to those of the other avialans. Based on this and an analysis of other traits, such as structure of the pelvis, toes and legs, they concluded that Archaeopteryx was a deinonychosaur, not an early bird.
This new ordering of the family tree only came out if the scientists included Xiaotingia in the comparison.
This is not the first time Archaeopteryx's place in bird evolution has been questioned. All of its bird-like features — its plumage, wishbone and three-fingered hands — also have been found in non-bird dinosaurs. And a 2010 study suggested that its metabolism was similar to a velociraptor's and that its heavy bones may have impeded it from flying.
But other experts said the case for shifting Archaeopteryx from bird to dinosaur status is not yet written in stone.
"We're still figuring things out," said Julia Clarke, a paleontologist at the University of Texas in Austin, who was not involved in the study.
Added Luis Chiappe, the director of the Dinosaur Institute at the Natural History Museum in Los Angeles, "I'm not 100% convinced of the results. We need to be cautious about embracing this proposal." Some of the fossils used to build the new tree are very fragmented, he said: Xiaotingia's remains, for example, were spread across five broken slabs of shale.
Also, the fossil's exact origins are hazy. The specimen — the only one of its kind — was bought from a dealer who could not provide accurate information about where it was found. The authors, however, wrote that the color, texture and size of the bones suggest they all belonged to the same animal and that the fossil is not a forgery.