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

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

Author information

1
Department of Zoology, Oregon State University, Corvallis, 97331, USA. quickd@science.oregonstate.edu

Abstract

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.

PMID:
19459194
DOI:
10.1002/jmor.10752
[Indexed for MEDLINE]

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