Unidirectional pulmonary airflow patterns in the savannah monitor lizard

Update Item Information
Publication Type pre-print
School or College College of Science
Department Biology
Creator Farmer, Colleen G.
Other Author Schachner, Emma R.; Cieri, Robert L.; Butler, James P.
Title Unidirectional pulmonary airflow patterns in the savannah monitor lizard
Date 2014-02-20
Description The unidirectional airflow patterns in the lungs of birds have long been considered a unique and specialized trait associated with the oxygen demands of flying, their endothermic metabolism1 and unusual pulmonary architecture2,3. However, the discovery of similar flow patterns in the lungs of crocodilians indicates that this character is probably ancestral for all archosaurs-the group that includes extant birds and crocodilians as well as their extinct relatives, such as pterosaurs and dinosaurs4-6. Unidirectional flow in birds results from aerodynamic valves, rather than from sphincters or other physical mechanisms7,8, and similar aerodynamic valves seem to be present in crocodilians4-6. The anatomical and developmental similarities in the primary and secondary bronchi of birds and crocodilians suggest that these structures and airflow patterns may be homologous4-6,9. The origin of this pattern is at least as old as the split between crocodilians and birds, which occurred in the Triassic period10. Alternatively, this pattern of flow may be even older; this hypothesis can be tested by investigating patterns of airflow in members of the outgroup to birds and crocodilians, the Lepidosauromorpha (tuatara, lizards and snakes). Here we demonstrate region-specific unidirectional airflow in the lungs of the savannah monitor lizard (Varanus exanthematicus). The presence of unidirectional flow in the lungs of V. exanthematicus thus gives rise to two possible evolutionary scenarios: either unidirectional airflow evolved independently in archosaurs and monitor lizards, or these flow patterns are homologous in archosaurs and V. exanthematicus, having evolved only once in ancestral diapsids (the clade encompassing snakes, lizards, crocodilians and birds). If unidirectional UU IR Author Manuscript UU IR Author Manuscript University of Utah Institutional Repository Author Manuscript Page 2 of 14 airflow is plesiomorphic for Diapsida, this respiratory character can be reconstructed for extinct diapsids, and evolved in a small ectothermic tetrapod during the Palaeozoic era at least a hundred million years before the origin of birds.
Type Text
Publisher Nature Publishing Group
First Page 1
Last Page 14
Language eng
Bibliographic Citation Schachner, E. R., Cieri, R. L., Butler, J. P., & Farmer, C. G. (2014). Unidirectional pulmonary airflow patterns in the savannah monitor lizard. Nature, 1-14.
Rights Management (c) Nature Publishing Group ; Schachner, E. R., Cieri, R. L., Butler, J. P., & Farmer, C. G. (2014). Unidirectional pulmonary airflow patterns in the savannah monitor lizard. Nature. doi:10.1038/nature12871
Format Medium application/pdf
Format Extent 7,892,374 bytes
Identifier uspace,18353
ARK ark:/87278/s6dz3jfg
Setname ir_uspace
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Reference URL https://collections.lib.utah.edu/ark:/87278/s6dz3jfg
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