Archaeopteryx knocked off its perch as first bird

FOR 150 years Archaeopteryx has been iconic as the earliest bird. 

The fossil sports feathered wings but a dinosaur's teeth and tail. Now the discovery of a feathered dinosaur in China has prompted a reassessment that has left Archaeopteryx squarely in dinosaur territory.

The diminutive new fossil, Xiaotingia zhengi, recently acquired by the Shandong Tianyu Museum of Nature from a fossil dealer, was excavated from 160-million-year-old rocks in Liaoning province (see the fossil here). 

It shares several key anatomical features with Archaeopteryx, including a "killing claw" on its second toe, and long and robust arms that probably allowed it to glide.

However, a team led by Xing Xu at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing deemed it sufficiently distinct from birds to be classified as a theropod dinosaur known as a deinonychosaur - and because of the similarities with Archaeopteryx, Xu's team concluded that the "first bird" is a deinonychosaur too (Nature, DOI: 10.1038/nature10288).

"We used to think Archaeopteryx was so different from other dinosaurs that it was ancestral to birds, but recent discoveries show that this is no longer the case," says Xu. "Our main conclusion is that Archaeopteryx is no longer a bird."

Other palaeontologists give Xu's findings a cautious welcome. "I am not surprised," says Gareth Dyke of University College Dublin in Ireland. "Flight may have evolved many times among small bodied theropod dinosaurs."

If Xu's analysis holds up it will create quite a headache for taxonomists as Archaeopteryx is used to define the base of the birds. 

One solution would be to include deinonychosaurs in the birds, says Luis Chiappe of the Natural History Museum of Los Angeles County, California.