New anatomical information on the bohaiornithid Longusunguis and the presence of a plesiomorphic diapsid skull in Enantiornithes

Abstract

Bohaiornithidae is currently the most diverse recognized family of Early Cretaceous enantiornithines, with unique morphology of the rostrum and pedal digits. Here we describe a second specimen of the bohaiornithid Longusunguis kurochkini from the Jiufotang Formation. This specimen provides new anatomical information regarding this taxon, in particular clarifying uncertain aspects of enantiornithine cranial morphology. The rarely preserved postorbital is completely preserved on both sides of the skull, confirming the presence of a complete postorbital bar in some enantiornithines. This suggests that the plesiomorphic diapsid skull was retained by at least some basal enantiornithines and the infratemporal fenestra in Ornithothoraces may have been lost independently multiple times, providing a better understanding of cranial evolution from non-avian dinosaurs to modern birds.

Keywords:

• Bohaiornithidae
• postorbital
• cranial evolution
• Early Cretaceous

Acknowledgements

We acknowledge D.-H. Li for specimen preparation, W. Gao for photography and P.-F. Yin for microcomputed laminography scans. This research was supported by an UNE Postdoctoral Research Fellowship, the State Key Laboratory of Paleobiology and Stratigraphy, Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences (CAS) grant no. 183110, Key Research Program of Frontier Sciences, CAS grant no. ZDBS-LY-DQC002, and the National Natural Science Foundation of China grant no. 41688103.

Supplementary material

Supplementary material for this article can be accessed here: https://doi.org/10.1080/14772019.2020.1748133.

Associate Editor: Victoria Arbour