New Bohaiornis -like bird from the Early Cretaceous of China: enantiornithine interrelationships and flight performance.

During the last decade, several Bohaiornis-like enantiornithine species-and numerous specimens-have been recognized from the celebrated Jehol Biota of northwestern China. In this paper, we describe the anatomy of another "bohaiornithid" species from the 125 million-year-old Yixian Formation of Liaoning Province, China. The new taxon differs from previously recognized "bohaiornithids" on a number of characters from the forelimb and shoulder girdle. We also provide a new phylogenetic framework for enantiornithine birds, which questions the monophyly of the previously recognized bohaiornithid clade and highlights ongoing challenges for resolving enantiornithine interrelationships. Additionally, we offer the first assessment of the flight properties of Bohaiornis-like enantiornithines. Our results indicate that while "bohaiornithids" were morphologically suited for flying through continuous flapping, they would have been unable to sustain prolonged flights. Such findings expand the flight strategies previously known for enantiornithines and other early birds.