Archosaurian respiration and the pelvic girdle aspiration breathing of crocodyliforms

• Published in: Proceedings of the Royal Society. B, Biological sciences Vol. 271; no. 1547; pp. 1461 - 1465
• Main Author: Claessens, Leon P. A. M.
• Format: Journal Article
• Language: English
• Published: England The Royal Society 22-07-2004
• Subjects: Accessory Breathing Mechanisms; Adaptation, Physiological - physiology; Alligator; Alligators; Alligators and Crocodiles - anatomy & histology; Alligators and Crocodiles - physiology; Amniota; Animals; Archosauria; Aves; Birds; Birds - anatomy & histology; Birds - physiology; Breathing; Cineradiography; Crocodylia; Dinosaurs - anatomy & histology; Dinosaurs - physiology; Girdles; Lungs; Pelvic Aspiration; Pelvic bones; Pelvic Bones - anatomy & histology; Pelvic Bones - physiology; Phylogeny; Pulmonary alveoli; Pulmonary Ventilation - physiology; Respiration; Respiratory mechanics; Spine; Ventilation systems
• ISSN: 0962-8452; 1471-2954
• DOI: 10.1098/rspb.2004.2743

Birds and crocodylians, the only living archosaurs, are generally believed to employ pelvic girdle movements as a component of their respiratory mechanism. This in turn provides a phylogenetic basis for inferring that extinct archosaurs, including dinosaurs, also used pelvic girdle breathing. I examined lung ventilation through cineradiography (high-speed X-ray filming) and observed that alligators indeed rotate the pubis to increase tidal volume, but did not observe pelvic girdle movement contributing to lung ventilation in guinea fowl, emus or tinamous, despite extensive soft-tissue motion. Re-examination of fossil archosaurs reveals that pubic rotation evolved in basal crocodyliforms and that pelvic girdle breathing is not a general archosaurian mechanism. The appearance of pelvic aspiration in crocodyliforms is a striking example of the ability of amniotes to increase gas exchange or circumvent constraints on respiration through the evolution of novel accessory breathing mechanisms.