A feathered dinosaur has been discovered that existed way before the bird-like dinosaurs that birds have generally been thought to have evolved from.
The find of the foot-long dinosaur from the Jurassic period - around 150 million years ago - challenges widely accepted theories on the origin of flight.
"This discovery sheds further doubt on the theory that the famous fossil Archaeopteryx - or 'first bird' as it is sometimes referred to - was pivotal in the evolution of modern birds," says Dr Gareth Dyke of the University of Southampton.
"Our findings suggest that the origin of flight was much more complex than previously thought."
It's generally been believed that birds evolved from a group of dinosaurs called theropods, dating from the Early Cretaceous period, around 120 to 130 million years ago. Recent discoveries of feathered dinosaurs from the older Middle-Late Jurassic period have reinforced this theory.
But the fossilized remains of Eosinopteryx, found in north-eastern China, indicate that it was flightless. While it did have feathers, its small wingspan and bone structure would have restricted its ability to flap its wings.
It also had toes suited to walking along the ground, and fewer feathers on its tail and lower legs, which would have made it easier to run.