found no trace of either melanosomes or metals in the majority of the wing feathers. They suggested that the wings of Confuciusornis would have been white or, possibly, colored with carotenoid pigments. The long tail feathers of male specimens would have also been dark in color along their entire length. A 2018 study of the specimen CUGB P1401 indicated the presence of heavy spotting on the wings, throat, and crest of Confuciusornis. Classification Hou assigned Confuciusornis to the Confuciusornithidae in 1995. At first he assumed it was a member of the Enantiornithes and the sister taxon of Gobipteryx. Later he understood that Confuciusornis was not an enantiornithean but concluded it was the sister taxon of the Enantiornithes, within a larger Sauriurae. This was heavily criticised by Chiappe who regarded Sauriurae to be paraphyletic as there were insufficient shared traits that indicated that the Confuciusornithidae and the Enantiornithes were closely related. In 2001, Ji Qiang suggested an alternative position as the sister taxon of the Ornithothoraces. In 2002 Ji's hypothesis was confirmed by a cladistic analysis by Chiappe, who defined a new group: the Pygostylia of which Confuciusornis is by definition the most basal member. Several traits of Confuciusornis show its position in bird evolution; it has a more "primitive" skull than Archaeopteryx, but it is the first known bird to have lost the long tail of Archaeopteryx and develop fused tail vertebrae, a pygostyle. One controversial study concluded that Confuciusornis may be more closely related to Microraptor and other dromaeosaurids than to Archaeopteryx, but this study was criticized on methodological grounds. The present standard interpretation of the phylogenetic position of Confuciusornis can be shown in this cladogram: A close relative, the confuciusornithid Changchengornis hengdaoziensis, also lived in the Yixian Formation. Changchengornis also possessed the paired, long tail feathers, as did several more advanced enantiornith birds. True, mobile tail fans only appeared in ornithuromorph birds, and possibly in the enantiornithine Shanweiniao. Paleobiology The large, fleshy phalangeal foot pads, small interphalangeal foot pads, presence of only reticulate scales on the underside of the foot (which increases flexibility), and curved foot claws of Confuciusornis are all traits shared with modern tree-dwelling, perching birds, suggesting that Confuciusornis may have had a similar lifestyle. Comparisons between the scleral rings supporting the eyes of Confuciusornis and modern birds and other reptiles indicate that it may have been diurnal, similar to most modern birds. Flight Confuciusornis has