A “bat-wing” dinosaur found in Jurassic rocks near Beijing has up-ended theories of the evolution of flight.
The discovery of the previously unknown species, which lived about 160 million years ago, suggests birds’ ancestors experimented with gliding long before they settled on powered flight.
Chinese researchers have dubbed the creature Yi qi — Mandarin for “strange wing” — after concluding that rod-shaped wrist bones helped the creature to fly. But although Yi qi also had feathers, they were too narrow to support flight.
Rather, the rat-sized animal flew using membranes like those on today’s bats and sugar gliders.
Scientists have long known that late species of “theropod” dinosaurs evolved into birds, with both groups possessing flight feathers. The new discovery, reported this morning in the journal Nature, suggests more primitive theropods — previously considered ground-dwellers — had taken to the air in a different way.
Lead author Xing Xu, of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, said Yi qi appeared to have evolved the same sorts of wings seen around a hundred millions years later in mammals. “No other bird or dinosaur had a wing of the same kind,” Professor Xu said.
University of California palaeontologist Kevin Padian said new feathered dinosaurs were discovered every month or so. “But things have just gone from the strange to the bizarre,” he wrote in a companion article in Nature.
“A feathered dinosaur from a completely unexpected branch of the dinosaur tree … sports a never-before-seen skeletal element that the authors think may be related to flight.”
Professor Padian said the evidence suggested the creature was incapable of powered flight because it could not flap its wings. At best, it glided like North America’s flying squirrels.
But he said flight was the only plausible explanation of the wrist bone’s function. And the theory was reinforced by remnants of “membranous tissue” near the wrists.
Makoto Manabe, of the National Museum of Nature and Science in Tokyo, said it was the first discovery of a dinosaur with membranous tissue.
Dr Manabe said flying membranes had evolved separately, tens of millions of years apart, in pterodactyls, dinosaurs and mammals. “The discovery shows that the evolution of flight is not as simple as previously thought.”
Tatsuya Hirasawa, of RIKEN Evolutionary Morphology Laboratory in Kobe, said the “incredible discovery” would force a rethink of the evolution of bird wings. “(It) will open doors to new and intriguing research topics.”