A new gansuid bird (Avialae, Euornithes) from the Lower Cretaceous (Aptian) Jiufotang Formation of Jianchang, western Liaoning, China

The study of the Cretaceous birds closest to the living euornithine species has mainly focused on the evolutionary patterns leading to the modern group. Yet, the morphological and ecological diversity of the euornithine branches not directly ancestral to the crown-group is probably underestimated. A new euornithine bird, Shuilingornis angelai gen. et sp. nov., is erected based on a nearly complete skeletal material from the Early Cretaceous (Aptian) Jehol Biota in western Liaoning, China. The new taxon is similar to the penecontemporary gansuids, yet it differs in the smaller body size and in the retention of plesiomorphic features widespread among non-gansuid euornithines. The osteohistological analysis indicates that Shuilingornis gen. nov. represents an early adult stage at the time of death. The phylogenetic analysis robustly supports the referral of Shuilingornis gen. nov. to Gansuidae. Except for the controversial Hollanda, the gansuids have been uncovered from four Aptian basins deposited under similar paleoclimatic conditions. Gansuid success in the middle part of the Cretaceous demonstrates that the exploration of semi-aquatic ecologies was a consistent euornithine pattern which preceded the later ornithurine radiation.