Paleontologists in China have discovered the fossils of a pigeon-sized feathered dinosaur that was bird-like in many ways, including that it possibly used its plumage to attract mates.
The remains of Epidexipteryx were found 90 per cent intact in Inner Mongolia's Nincheng County in northern China, the scientists wrote in the journal Nature on Wednesday.
It likely lived in the middle to late Jurassic periods, or between 146 million and 176 million years ago.
That would make it older than Archaeopteryx, the most commonly known dinosaur thought to be an ancestor of birds. Archaeopteryx lived 150 million to 155 million years ago.
The tiny dinosaur weighed an estimated 164 grams and shared many features found in birds, but also appeared to be closely related to Oviraptorosaurs, a group of tiny dinosaurs with distinctive short, high skulls.
The fossil also possessed a number of skeletal features unusual among dinosaurs, such as a particularly short pubis, one of the three bones forming the pelvis.
The dinosaur lacked the contour feathers necessary for flight, although it had two pairs of elongated tail feathers, part of ornamental plumage in modern birds.
The researchers suggest that as with today's birds, the elongated feathers would be used to send a variety of visual signals to other birds, including for courtship.
Epidexipteryx is the oldest therapod — a group of bipedal dinosaurs that includes Tyrannosaurus rex — to possess "display" feathers, they said.
The finding suggests display feathers may have appeared before feathers used to aid flight, they wrote.