HONG KONG (Reuters) - Chinese researchers have unearthed the fossil of a bird-like dinosaur with four wings in northeastern China, which they suggest is a missing link in dinosaurs' evolution into birds.
In a paper in the journal Nature, they said they found the well-preserved fossil of the "Anchiornis huxleyi," which roamed the earth some 160 million years ago, in a geological formation in China's northeastern Liaoning province.
About the size of a chicken, the fossil has a total body length of less than 50cm (20 inches) and a skull about 6cm long, lead researcher Xing Xu at the Chinese Academy of Science in Beijing told Reuters in an email.
"This finding suggests that birds are likely to be descended from a kind of small-sized four-winged dinosaur about 160 million years ago," Xu said.
"It is a link between more typical theropods (dinosaurs which moved around with two rear limbs) and birds. It lived around a time period ... that we expected for birds' ancestor."
In a statement, the researchers said: "Long feathers cover the arms and tail, but also the feet, suggesting that a four-winged stage may have existed in the transition to birds."
The transition from dinosaurs to birds is still poorly understood because of the lack of well-preserved fossils, and many scientists say bird-like dinosaurs appear too late in the fossil record to be the true ancestors of birds.
The Chinese researchers believe the fossil is the oldest bird-like dinosaur reported so far, and older than Archaeopteryx, the earliest known bird.
"The presence of such a species at this time in the fossil record effectively disputes the argument that bird-like dinosaurs appeared too late to be the ancestors of birds," they wrote.
(Reporting by Tan Ee Lyn; Editing by Jerry Norton)