The first Chinese discoveries of these feathered limbs were made at the turn of this century in dinosaur species named Microraptor and Sinornithosaurus. It is widely accepted that the large leg feathers in Microraptor were used in aerial locomotion, either in powered flight or merely gliding between trees or parachuting to the ground.

Although the new findings confirmed the presence of four-feathered wings early in the bird lineage as well, the Chinese scientists conceded that the aerodynamic function of this configuration remains debatable. Yet the research team, led by Zheng Xiaoting, of the Shandong Tianyu Museum of Nature, wrote that the stiff vanes and curving feathers in certain dinosaurs and the basal birds were “aerodynamic in function, providing lift, creating drag and/or enhancing maneuverability, and thus played a role in flight.”

The research team, which also included Xu Xing, a prominent dinosaur investigator at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, examined fossils found in Liaoning Province in northeastern China, a mother lode of remains from the early Cretaceous period. The work on the 11 basal bird specimens, which included several Sapeornis, Yanornis and Confuciusornis species, was conducted mainly at the Shandong Tianyu Museum of Nature.

Dr. Zheng’s group acknowledged that the way many of the specimens were preserved, revealed only in two dimensions, made it difficult to reconstruct the precise location and orientation of the leg feathers. Each skeleton, for example, is preserved either with the legs splayed outward or with the legs in a crouched position under the body. Nevertheless, the researchers wrote, “there is circumstantial data that might be useful in inferring the distribution and orientation of leg feathers.”

Generally, the leg feathers of modern birds, if they exist at all, are less developed than the arm feathers. They are usually small and fluffy, as in some chickens and pouter pigeons. They presumably serve to protect and insulate the legs, not to help in flight.