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.

渤海科是目前公认的最广泛的早白垩世对映体科，其讲台和脚趾手指形态独特。在这里，我们描述了bohaiornithid Longusunguis kurochkini的第二个标本来自九佛堂组。该标本提供了有关该分类单元的新的解剖学信息，尤其是阐明了对映鸟氨酸颅骨形态的不确定方面。很少保存的眶后被完全保留在颅骨的两侧，这证实了在某些对映鸟氨酸中存在完整的眶后条。这表明至少有一些基础对映鸟氨酸保留了类异形的双翅类颅骨，而鸟巢动物的颞下窗可能已经多次独立丢失，从而更好地了解了从非禽类恐龙到现代鸟类的颅骨进化。