Cardio-pulmonary anatomy in theropod dinosaurs: Implications from extant archosaurs

J Morphol. 2009 Oct;270(10):1232-46. doi: 10.1002/jmor.10752.


Although crocodilian lung and cardiovascular organs are markedly less specialized than the avian heart and lung air-sac system, all living archosaurs possess four-chambered hearts and heterogeneously vascularized, faveolar lungs. In birds, normal lung function requires extensive, dorsally situated nonvascularized abdominal air-sacs ventilated by an expansive sternum and specially hinged costal ribs. The thin walled and voluminous abdominal air-sacs are supported laterally and caudally to prevent inward (paradoxical) collapse during generation of negative (inhalatory) pressure: the synsacrum, posteriorly directed, laterally open pubes and specialized femoral-thigh complex provide requisite support and largely prevent inhalatory collapse. In comparison, theropod dinosaurs probably lacked similarly enlarged abdominal air-sacs, and skeleto-muscular modifications consistent with their ventilation. In the absence of enlarged, functional abdominal air-sacs, theropods were unlikely to have possessed a specialized bird-like, air-sac lung. The likely absence of bird-like pulmonary function in theropods is inconsistent with suggestions of cardiovascular anatomy more sophisticated than that of modern crocodilians.

MeSH terms

  • Air Sacs / anatomy & histology
  • Alligators and Crocodiles / anatomy & histology
  • Animals
  • Birds / anatomy & histology
  • Bone and Bones / anatomy & histology
  • Dinosaurs / anatomy & histology*
  • Heart / anatomy & histology*
  • Lung / anatomy & histology*
  • Pelvis / anatomy & histology