Early diversification of birds: Evidence from a new opposite bird

Abstract

A new enantiornithine bird Longipteryx chaoyangensis gen. et sp. nov. is described from the Early Cretaceous Jiufotang Formation in Chaoyang, western Liaoning Province. This new bird is distinguishable from other known enantiornithines in having uncinate processes in ribs, elongate jaws, relatively long wings and short hindlimbs, and metatarsal IV longer than metatarsals II and III. This new bird had probably possessed (i) modern bird-like thorax which provides firm attachment for muscles and indicates powerful and active respiratory ability; (ii) powerful flying ability; (iii) special adaptation for feeding on aquatic preys; and (iv) trochleae of metatarsals I-IV almost on the same level, an adaptation for perching. The new bird represents a new ecological type different from all known members of Enantiornithes. It shows that enantiornithines had probably originated earlier than the Early Cretaceous, or this group had experienced a rapid radiation right after it first occurred in the early Early Cretaceous.