Wedel Mathew John
University of California Museum of Paleontology, Berkeley, California, USA.
J Exp Zool A Ecol Genet Physiol. 2009 Oct 1;311(8):611-28. doi: 10.1002/jez.513.
Among extant tetrapods, pneumatic postcranial bones are only present in birds, and they are osteological correlates of the diverticular lungs and pulmonary air sacs. The presence of postcranial pneumaticity in sauropod and theropod dinosaurs suggests that some form of air sac system was also present in the dinosaurian ancestors of birds. In particular, anatomical and evolutionary patterns of pneumatization in nonavian saurischian dinosaurs are diagnostic for specific air sacs, including the cervical, clavicular, and abdominal air sacs. Pneumatic hiatuses are gaps in the pneumatization of the vertebral column and indicate pneumatization from multiple sources. A pneumatic hiatus in Haplocanthosaurus provides additional support for the presence of abdominal air sacs in sauropods. The origins of postcranial pneumaticity in archosaurs are enigmatic because the earliest putative traces of pneumaticity are difficult to distinguish from skeletal imprints of other soft tissues. Nevertheless, several lines of evidence suggest that air sac-driven lung ventilation was primitive for Saurischia.
在现存的四足动物中，颅后气骨仅存在于鸟类中，它们是憩室肺和肺气囊的骨骼关联物。蜥脚类恐龙和兽脚类恐龙中颅后气腔的存在表明，鸟类的恐龙祖先中也存在某种形式的气囊系统。特别是，非鸟类蜥臀目恐龙的气腔形成的解剖学和进化模式对于特定的气囊具有诊断意义，包括颈气囊、锁间气囊和腹气囊。气腔间隙是脊柱气腔化过程中的间隙，表明有多个来源的气腔化。哈氏龙的一个气腔间隙为蜥脚类恐龙存在腹气囊提供了额外支持。主龙类颅后气腔的起源尚不清楚，因为最早假定的气腔痕迹很难与其他软组织的骨骼印记区分开来。然而，几条证据表明，气囊驱动的肺通气是蜥臀目的原始特征。
