Chinese paleontologists have discovered the fossil of an extraordinary, previously unknown four-winged dinosaur, throwing fresh kindling on a smouldering century-old debate about the origin of birds.

The discovery represents a remarkable posthumous vindication for the legendary American naturalist William Beebe, who in 1915 proposed that today's flying birds evolved through a stage of gliding dinosaurs with feathers on all four limbs. More than 40 years after Beebe's death, that is exactly what the Chinese team has unearthed in Liaoning, north-east of Beijing.

"It looks as if it could have glided straight out of the pages of Beebe's notebooks," said Richard Prum, a biologist from Kansas, in Nature, where the latest find was published.

The vivid remains of the dinosaur, like a snapshot of the instant of its death in flight, were found by a team led by Xing Xu of Beijing's Institute of Vertebrate Paleontology. They named the new species Microraptor gui.

Some 125m years ago, Xu and colleagues propose, it would have been gliding between the treetops by an ancient lake shore, using all four feathered limbs and a long, resplendently feathered tail for flight.

For the past century an argument has raged as to how birds' power of flight evolved; was it from tree-dwelling gliders, or from ground dwellers who used early wings to help them move forward more quickly?

Xu and his team are promoting Microraptor gui as strong evidence for gliding, feathered dinosaurs as the ancestors of today's birds.

"What's really, really cool about it is it has feathers on its hindlimbs as well as its forelimbs," said Gareth Dyke, a bird evolution specialist at University College Dublin. "It seems to have been able to use both for aerodynamic function, which suggest gliding."

Angela Milner, a dinosaur specialist at the Natural History Museum in London, where previous Chinese dino-bird fossils are featuring in an exhibition, said: "It adds weight to the theory that flight may have arisen in small tree-climbing dinosaurs through a gliding stage."