Bird display both clearly traditional reptilian characteristics: teeth, clawed fingers, and a long, lizard-like tail, as well as wings with flight feathers similar to those of modern birds. It is not considered a direct ancestor of birds, though it is possibly closely related to the true ancestor. The earliest known avialan fossils come from the Tiaojishan Formation of China, which has been dated to the late Jurassic period (Oxfordian stage), about 160 million years ago. The avialan species from this time period include "Anchiornis huxleyi", "Xiaotingia zhengi", and "Aurornis xui". The well-known early avialan, "Archaeopteryx", dates from slightly later Jurassic rocks
Archaeopteryx be black throughout, with heavier pigmentation in the distal tip. The feather studied was most probably a dorsal covert, which would have partly covered the primary feathers on the wings. The study does not mean that "Archaeopteryx" was entirely black, but suggests that it had some black colouration which included the coverts. Carney pointed out that this is consistent with what we know of modern flight characteristics, in that black melanosomes have structural properties that strengthen feathers for flight. In a 2013 study published in the "Journal of Analytical Atomic Spectrometry", new analyses of "Archaeopteryx"'s feathers revealed that the animal