All birds, even ones that perch in trees, may have descended from waterfowl. That is the conclusion of a study of well preserved 110-million-year-old fossils of the earliest known modern bird. The specimens were found in northwestern China.
U.S. and Chinese geologists dug up several nearly complete three-dimensional fossil imprints of uncrushed, loon-like birds called Gansus. They are named for the Gansu region, 2,000 kilometers west of Beijing, where they were found in rocks that used to be the muddy bottom of an old lake. Only the fossils' heads and upper necks are missing.
The remains show their structure in rich detail, leading one of the scientists to say that the birds' features are strikingly modern for 110-million years of age.
"No other fossil bird of this age, and even some fossil birds that are much younger than Gansus, has this same suite of modern style features," said Jerald Harris of Dixie State College in Utah, speaking at a Washington news briefing held by the journal Science, in which the study appears.
"Gansus is, therefore, the oldest known bird that is this modern in its anatomy," he said. "It helps us fill a gap in the evolutionary progression towards modern birds."
Harris says this is important because most of the birds from the age of the dinosaurs, when birds first appeared, were from species that have become extinct. Gansus is a link to those earlier groups.
The bird skeletons, although headless, offer plenty of evidence for an amphibious life. Their upper body structure shows that Gansus could take flight from water like a modern duck. The webbed feet and bony knees are clear signs that Gansus swam.
Co-discoverer Matthew Lamanna of the Carnegie Museum of Natural History in Pittsburgh says Gansus is not the only ancient member of this bird lineage to show aquatic features. Older fossils do, too.
"This observation significantly strengthens a long-standing hypothesis that the origins of all modern birds - every one of the 10,000 bird species living today - probably took place in aquatic environments," said Matthew Lamanna. "Every bird living today, from ostriches to eagles to hummingbirds, probably evolved from a Gansus-like ancestor."
Jerald Harris says Gansus might not have been as good a diver as modern birds, but probably could compete with them adequately.
"In terms of its actual behavior and abilities, I do not think it would have been very much different than some of the birds we see today," he said.