A uniquely specialized ear in a very early tetrapod

Clack, J. A. and Ahlberg, P. E. and Finney, S. M. and Dominguez Alonso, P. and Robinson, J. and Ketcham, R. A. (2003) A uniquely specialized ear in a very early tetrapod. Nature, 425 (6953). pp. 65-69. DOI https://doi.org/10.1038/nature01904

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The Late Devonian genus Ichthyostega was for many decades the earliest known tetrapod, and the sole representative of a transitional form between a fish and a land vertebrate. However, despite being known since 1932 (ref. 1) from a large collection of specimens, its morphology remained enigmatic and not what was expected of a very primitive tetrapod2. Its apparent specializations led it to be considered as a "blind offshoot"3 or "sidebranch"4 off the tetrapod family tree, and recent cladistic analyses have disagreed about its exact phylogenetic position5, 6, 7, 8 within the tetrapod stem group. In particular, its braincase and ear region defied interpretation, such that conventional anatomical terms seemed inapplicable4. Using new material collected in 1998 (ref. 9), preparation of earlier-collected material, and high-resolution computed tomography scanning, here we identify and interpret these problematic anatomical structures. They can now be seen to form part of a highly specialized ear, probably a hearing device for use in water. This represents a structurally and functionally unique modification of the tetrapod otic region, unlike anything seen in subsequent tetrapod evolution. The presence of deeply grooved gill bars as in its contemporary Acanthostega 10 suggest that Ichthyostega may have been more aquatically adapted than previously believed.

Item Type: Article
Uncontrolled Keywords: 2003 AREP 2003PUBL IA44A
Subjects: 04 - Palaeobiology
Divisions: 04 - Palaeobiology
Journal or Publication Title: Nature
Volume: 425
Page Range: pp. 65-69
Identification Number: https://doi.org/10.1038/nature01904
Depositing User: Sarah Humbert
Date Deposited: 26 Nov 2011 12:37
Last Modified: 23 Jul 2013 10:02
URI: http://eprints.esc.cam.ac.uk/id/eprint/2252

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