Confuciusornithidae is an extinct family of pygostylian avialans known from the Early Cretaceous, found in northern China.

Some specimens probably referable to this clade represents one of the earliest known fossil evidence of primary feather moulting.

They possessed feathers similar to those of fast-flapping birds, which rely on quick flapping of their wings to stay aloft.

[2] The group was given a phylogenetic definition by Chiappe, in 1999, who defined a node-based clade Confuciusornithidae to include only Changchengornis and Confuciusornis.

The other defining features are as follows, according to Chiappe et al. (1999):[3] Confuciusornithidae is the most basal group of the clade Pygostylia, whose members possess a pygostyle, a fused set of caudal vertebrae at the end of the tail.

The pygostyle replaced the longer, unfused tail found in more primitive avialans such as Archaeopteryx,[3] and may have served to improve flight.

[7] The development of a pygostyle also shows better adaptation for flight, as this replaces the long tails present in earlier avialans.

[6] However, their anatomy was not adapted for plant consumption, as gastroliths have never been found, nor did the weak rhamphotheca of the beak allow for grinding.

[6] Large numbers of fossils appear to originate from the tops of freshwater lakes, further supporting the water feeding connection.

[11] Confuciusornithids appear to have been social animals, as concurrently buried fossils are often found in close proximity.

[12] Other paravians (including Deinonychus) and pterosaurs are known to be superprecocial and able to fly soon after birth,[13][14][15] but for now there are no unambiguous confuciusornithid juveniles to attest this.