Abstract: Previously known only from the holotype specimen, Pengornis houi is the largest known Early Cretaceous enantiornithine bird and important for understanding body size and character evolution in Ornithothoraces. We report on a new subadult specimen from the Lower Cretaceous Jiufotang Formation referred to Pengornis sp. The specimen preserves a nearly complete sternum, reminiscent of that in Protopteryx and the basal ornithuromorph Archaeorhynchus, confirming the basal position of Pengornis and shedding new light on the evolution of the sternum in ornithothoracines. Anatomical information suggests that despite its size, Pengorniswas arboreal, like other enantiornithines.

摘要： 鹏鸟(Pengornis)是早白垩世已知体型最大的反鸟类，其骨骼兼有反鸟类和今鸟类的特征。报道了辽西九佛堂组新发现的一件鹏鸟的亚成年个体标本，代表了该属鸟类除侯氏鹏鸟(Pengornis houi)正型标本外的已知第二件标本，暂归入鹏鸟未定种(Pengornis sp.)。该标本头骨与头后骨骼近乎完整保存，并附有羽毛印痕，仅缺失部分右前肢和部分左后肢。新标本首次提供了鹏鸟胸骨与基干反鸟类原羽鸟(Protopteryx)及基干今鸟类古喙鸟(Archaeorhynchus)相似的形态特征，肯定了鹏鸟的基干位置，并讨论了其在鸟类胸骨演化中的意义。新标本对前肢和后肢(特别是脚趾)等的许多特征也有补充，表明其应当属于树栖生活的鸟类。