HONG KONG (Reuters) - Archaeologists in China have discovered fossils of a pigeon-sized feathered dinosaur which they believe to be an ancestor of birds.

Its remains were found 90 percent complete, preserved in a slab of rock in Inner Mongolia’s Ningcheng county in northern China, the researchers wrote in an article in Nature.

Its four limbs lacked contour feathers for flight and it probably lived from the Middle to Late Jurassic periods, or 176 to 146 million years ago.

This means it is older than the Archaeopteryx, which lived around 155 to 150 million years ago.

Feathered but flightless, the small creature weighed just 164 grams and had buck teeth resembling that of carnivores.

But scientists have no clue what it ate.

“Insects? Other reptiles or amphibians? Or plants?” Professor Fucheng Zhang of the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences wrote in reply to a question from Reuters regarding its diet.

Named the Epidexipteryx, it had four long and thin tail feathers and a short tail.

The scientists said it belonged to a different group from the Microraptor, which had flight feathers and which some scientists believe flew sometimes in addition to gliding.

But like the Microraptor -- which lived in a later period 130 to 125 million years ago -- it gave important evidence about the evolutionary relationship between birds and dinosaurs.

“You could say it was a link between dinosaur and birds. It was very close to the ancestor of birds,” Zhang wrote.

“This new fossil adds yet more complexity to the early history of evolution from dinosaurs to birds.”