Confuciusornis

Confuciusornis, genus of extinct crow-sized birds that lived during the Late Jurassic and Early Cretaceous (roughly 161 million to 100 million years ago). Confuciusornis fossils were discovered in the Chaomidianzi Formation of Liaoning province, China, in ancient lake deposits mixed with layers of volcanic ash. These fossils were first described by Hou Lianhai and colleagues in 1995. Confuciusornis was about 25 cm (roughly 10 inches) from beak to pelvis. It possessed a small triangular snout and lacked teeth.

Confuciusornis held a number of physical characteristics in common with modern birds but possessed some striking differences. Beautifully preserved specimens show impressions of its feathers, from which it can be inferred that the wings were of comparable size to those of similar flying birds today. Unlike modern birds, however, the forearm of Confuciusornis was shorter than both its hand and upper arm bone (humerus). It also retained the feature of having three free fingers on the hand, like Archaeopteryx and other theropod dinosaurs. In contrast, the fingers of more-derived birds are fused into an immobile element. Confuciusornis had a short tail, a common feature in modern birds, and its caudal vertebrae were reduced in size and number. The terminal vertebrae were fused to form a structure known as the pygostyle. In some specimens, as in the related Changchengornis, a pair of long, thin feathers proceeded from each side of the tail and expanded distally into a teardrop-shaped surface. It has been suggested that these feathers were sexually dimorphic structures and possibly indicative of males. To date, this hypothesis has not been tested statistically or corroborated by other dimorphic features.

Whereas most living birds (including the ostrich) reach full size within a year, the internal bone structure of Confuciusornis shows that it grew more slowly. Like other small dinosaurs, Confuciusornis probably took several years to mature. This evidence suggests that birds apparently did not evolve their rapid growth rates until sometime in the Late Cretaceous.

Local farmers living in or near the Chaomidianzi Formation collected the first known remains of Confuciusornis. Although a good number of specimens have been deposited in Chinese museums, many more have been sold illegally to commercial fossil dealers.