London, May 3 : A well preserved Chinese fossil of an ancient bird might be the missing link between the oldest known bird, Archaeopteryx, and more advanced birds.
According to a report in New Scientist, the newly discovered fossil is of an ancient bird known as Eoconfuciusornis, which scientists have speculated to be the link between Archaeopteryx, and more advanced birds that have been discovered in the Yixian geological formation in China.
The Yixian deposits have yielded remarkably diverse fauna that have revolutionised avian palaeontology, but they are limited to a period from 125 to 120 million years ago - too narrow a time span to show much evidence of evolution within bird lineages.
A huge interval separates the Yixian birds from Archaeopteryx, which lived about 150 million years ago, leaving a gap in scientists' knowledge of bird evolution over this period.
But, Eoconfuciusornis was found in different deposits, known as the Dabeigou formation, and falls within the gap - radiometric dating providing evidence that it lived 131 million years ago.
The new find is closely related to Confuciusornis - the most abundant Yixian fossil bird, with thousands of examples known. The two share skeletal features, as well as toothless horny bills and distinctive long paired tail feathers.
According to Mike Benton of the University of Bristol, UK, co-author of a description of Eoconfuciusornis, "The new discovery gives us a span of 11 million years of history for the Confuciusornis family, long enough to show patterns of evolution."
Avian evolution made important advances between Archaeopteryx and the Yixian birds.
"Archaeopteryx was an efficient powered flapping flyer, but lacked many of the adaptations of the skeleton seen in modern birds - especially fusions of bones that support flight muscle and reduce length of the tail," Benton told New Scientist.
On the other hand, Confuciusornis was a strong flyer, with flight muscles anchored on the wing by a large ridge of bone known as the deltopectoral crest, and on the body by a large fused sternum.
With a pair of separate sternal plates and a smaller deltopectoral crest, Eoconfuciusornis is more advanced then Archaeopteryx, and the most primitive, as well as the earliest, member of the Confuciusornis family.
According to Larry Martin, a palaeontologist at the University of Kansas, Lawrence, US, "I think they are dead-on, absolutely correct in placing the new fossil in the crucial gap."