Data from: Ventilatory mechanics from maniraptoran theropods to extant birds

Shared behavioural, morphological and physiological characteristics are indicative of the evolution of extant birds from non-avian maniraptoran dinosaurs. One such shared character is the presence of uncinate processes; respiratory structures in extant birds. Recent research has suggested a respiratory role for these processes found in oviraptorid and dromaeosaurid dinosaurs. By measuring the geometry of fossil rib cage morphology we demonstrate that the mechanical advantage, conferred by uncinate processes, for movements of the ribs in the oviraptorid theropod dinosaur, Citipati osmolskae, basal avialan species Zhongjianornis yangi, Confuciusornis sanctus, and the more derived ornithurine Yixianornis grabaui, is of the same magnitude as found in extant birds. These skeletal characteristics provide further evidence of a flow-through respiratory system in non-avian theropod dinosaurs and basal avialans, and indicate that uncinate processes are a key adaptation facilitating the ventilation of a lung air sac system that diverged earlier than extant birds.共有行为学、形态学与生理学特征，可作为现生鸟类（extant birds）起源于非鸟类手盗龙类恐龙（non-avian maniraptoran dinosaurs）的演化佐证。此类共有特征之一为肋钩突（uncinate processes）的存在，该结构在现生鸟类中属于呼吸相关结构。近期研究表明，在窃蛋龙类（oviraptorid）与驰龙科（dromaeosaurid）恐龙中发现的这类结构具备呼吸相关功能。本研究通过量化分析化石胸廓形态的几何特征，证实窃蛋龙类兽脚类（theropod）恐龙奥氏西庇太盗龙（Citipati osmolskae）、基干鸟类（basal avialan）物种杨氏中健鸟（Zhongjianornis yangi）、圣贤孔子鸟（Confuciusornis sanctus），以及更为衍化的今鸟型类（ornithurine）葛氏义县鸟（Yixianornis grabaui）中，肋钩突赋予肋骨运动的机械优势程度，与现生鸟类中的水平相当。这些骨骼特征进一步为非鸟类兽脚类恐龙与基干鸟类具备流式呼吸系统（flow-through respiratory system）提供了新的佐证，并表明肋钩突是一项关键适应性特征，可助力肺气囊系统（air sac system）的通气功能——该系统的分化时间早于现生鸟类。