The fossil evidence for the animal pre-dates that of Archaeopteryx lithographica, often considered the earliest bird species, by about 10 million years.

[1][2] Aurornis xui was first described and named by Pascal Godefroit, Andrea Cau, Hu Dong-Yu, François Escuillié, Wu Wenhao and Gareth Dyke in 2013.

Subsequent analysis confirmed it came from the Tiaojishan Formation, which has been dated to the late Jurassic period (Oxfordian stage), approximately 160 million years ago.

The failure to secure rigorous provenance information casts doubt on the claim that Aurornis is 160 million years old and predates Archaeopteryx.

Godefroit's team will attempt to confirm the specimen's provenance, and its age, by conducting mineralogical and botanical analysis on the shale slab and then publishing their findings.

Recent discoveries "[emphasize] how grey the dividing line is between birds and [non-avian] dinosaurs", says Paul Barrett of the Natural History Museum in London.

He thought they must have represented an intermediate ecological stage, in which the hindlimbs still had largely cursorial adaptations whereas the arms had been elongated in order to climb.

Feathers, originally serving the insulation of an already warm-blooded animal, would by elongation have turned the arms into wings in order to fly.