Dozens of fossils of an ancient loon-like creature that some say is the missing link in bird evolution have been discovered in northwest China.
The remains of 40 of the nearly modern amphibious birds, so well-preserved that some even have their feathers, were found in Gansu province, researchers report in Friday's issue of the journal Science. Previously only a single leg of the creature, known as Gansus yumenensis, had been found.
"Gansus is a missing link in bird evolution," said Matt Lamanna of the Carnegie Museum of Natural History in Pittsburgh.
"Most of the ancestors of birds from the age of dinosaurs are members of groups that died out and left no modern descendants. But Gansus led to modern birds, so it's a link between primitive birds and those we see today," Lamanna, a co-leader of the research team, said in a telephone interview.
It was about the size of a modern pigeon, but similar to loons or diving ducks, he explained, and one of the fossils even has skin preserved between the toes, showing that it had webbed feet.
"We were lucky far beyond our expectations" in finding these fossils, Hai-lu You of the Chinese Academy of Geological Sciences said at a briefing Thursday.
"A world lost for more than 100 million years was being revealed to us," he said.
Previously there was a gap between ancient and modern species of birds, and "Gansus fits perfectly into this gap," added Jerald D. Harris of Dixie State College in Utah.
"Gansus is the oldest example of the nearly modern birds that branched off of the trunk of the family tree that began with the famous proto-bird Archaeopteryx," said Peter Dodson of the University of Pennsylvania, a co-author of the paper along with Lamanna, You and others.
The remains were dated to about 110 million years ago, making them the oldest for the group Ornithurae, which includes all modern birds and their closest extinct relatives. Previously, the oldest known fossils from this group were from about 99 million years ago.