A caseian point for the evolution of a diaphragm homologue among the earliest synapsids
The origin of the diaphragm remains a poorly understood yet crucial step in the evolution of terrestrial vertebrates, as this unique structure serves as the main respiratory motor for mammals. Here, we analyze the paleobiology and the respiratory apparatus of one of the oldest lineages of mammal‐lik...
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Published in | Annals of the New York Academy of Sciences Vol. 1385; no. 1; pp. 3 - 20 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
United States
Blackwell Publishing Ltd
01.12.2016
Wiley Subscription Services, Inc |
Subjects | |
Online Access | Get full text |
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Summary: | The origin of the diaphragm remains a poorly understood yet crucial step in the evolution of terrestrial vertebrates, as this unique structure serves as the main respiratory motor for mammals. Here, we analyze the paleobiology and the respiratory apparatus of one of the oldest lineages of mammal‐like reptiles: the Caseidae. Combining quantitative bone histology and functional morphological and physiological modeling approaches, we deduce a scenario in which an auxiliary ventilatory structure was present in these early synapsids. Crucial to this hypothesis are indications that at least the phylogenetically advanced caseids might not have been primarily terrestrial but rather were bound to a predominantly aquatic life. Such a lifestyle would have resulted in severe constraints on their ventilatory system, which consequently would have had to cope with diving‐related problems. Our modeling of breathing parameters revealed that these caseids were capable of only limited costal breathing and, if aquatic, must have employed some auxiliary ventilatory mechanism to quickly meet their oxygen demand upon surfacing. Given caseids’ phylogenetic position at the base of Synapsida and under this aquatic scenario, it would be most parsimonious to assume that a homologue of the mammalian diaphragm had already evolved about 50 Ma earlier than previously assumed. |
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Bibliography: | ark:/67375/WNG-P02CZSXR-0 Deutsche Forschungsgemeinschaft - No. Sa 469/34-1 ArticleID:NYAS13264 istex:098785A913B4C265E164AFB5A01B9EA1065323CE ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0077-8923 1749-6632 |
DOI: | 10.1111/nyas.13264 |