A new ornithuromorph (Aves) with an elongate rostrum from the Jehol Biota, and the early evolution of rostralization in birds

A new species of Early Cretaceous ornithuromorph with an elongate rostrum is described from the Sihedang locality of the Lower Cretaceous Yixian Formation in north-eastern China. Like the longipterygid enantiornithines, rostral elongation in Dingavis longimaxilla gen. et sp. nov. is achieved primarily through the maxilla, whereas neornithines elongate the premaxilla and rostralization is far more extreme than observed in early birds. Notably, in the rostrum of Xinghaiornis, the most ‘longirostrine’ Early Cretaceous ornithuromorph, the premaxilla and maxilla contribute to the rostrum equally. These lineages together highlight the diversity of configurations in which early birds experimented with rostralization of the skull. The 65% upper limit in rostral proportions of Early Cretaceous taxa with elongate maxillae and the fact that this morphology was abandoned in more derived taxa suggests that in Aves this skull configuration provided less structural stability.

http://zoobank.org/urn:lsid:zoobank.org:pub:9D8A429F-BBA7-47EF-BFD0-ADFB7118833A