Schachner Emma R, Lyson Tyler R, Dodson Peter
Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Anat Rec (Hoboken). 2009 Sep;292(9):1501-13. doi: 10.1002/ar.20989.
Recent reports of region-specific vertebral pneumaticity in nonavian theropod dinosaurs have brought attention to the hypothesis that these animals possessed an avian-style respiratory system with flow-through ventilation. This study explores the thoracic rib and vertebral anatomy of Sinraptor, Allosaurus, Tyrannosaurus, and Deinonychus; four nonavian theropods that all show well-preserved thoracic vertebrae and ribs. Comparisons to the osteology and soft tissue anatomy of extant saurians provide new evidence supporting the hypothesis of flow-through ventilation in nonavian theropods. Analyses of diapophyseal and parapophyseal position and thoracic rib morphology suggest that most nonavian theropods possessed lungs that were deeply incised by the adjacent bicapitate thoracic ribs. This functionally constrains the lungs as rigid nonexpansive organs that were likely ventilated by accessory nonvascularized air sacs. The axial anatomy of this group also reveals that a crocodilian-like hepatic-piston lung would be functionally and biomechanically untenable. Taken together with the evidence that avian-like air sacs were present in basal theropods, these data lead us to conclude that an avian-style pulmonary system was likely a universal theropod trait.
近期关于非鸟兽脚亚目恐龙特定区域椎体含气性的报道，使人们开始关注这样一种假说：这些动物拥有类似鸟类的呼吸系统，具备流通式通气。本研究探究了中华盗龙、异特龙、霸王龙和恐爪龙的胸肋及椎体解剖结构；这四种非鸟兽脚亚目恐龙的胸椎和肋骨均保存完好。与现存蜥蜴类的骨骼学和软组织解剖结构进行比较，为支持非鸟兽脚亚目恐龙存在流通式通气的假说提供了新证据。对横突和副突位置以及胸肋形态的分析表明，大多数非鸟兽脚亚目恐龙的肺部被相邻的双头胸肋深深切入。这在功能上限制了肺部成为刚性的、不可扩张的器官，这些器官可能由辅助的无血管气囊进行通气。该类群的轴向解剖结构还表明，类似鳄鱼的肝活塞肺在功能和生物力学上是站不住脚的。结合基础兽脚亚目恐龙存在类似鸟类气囊的证据，这些数据使我们得出结论：类似鸟类的呼吸系统可能是兽脚亚目恐龙的普遍特征。
