Eel-like swimming in the earliest ichthyosaurs (original) (raw)
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- Published: 25 July 1996
Nature volume 382, pages 347–348 (1996)Cite this article
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Abstract
ICHTHYOSAURS are extinct marine reptiles, probably belonging to the Diapsida1, that ranged from the Early Triassic to Late Cretaceous2,3. Post-Triassic ichthyosaurs achieved the highest level of aquatic adaptation among reptiles4, with a streamlined body, lunate tail and a dorsal fin, features exemplified today by thunniform (tuna-like) fishes. However, little is known of how such a body plan evolved from a terrestrial diapsid. Here we report the most complete specimen of the oldest known ichthyosaur, Chensaurus, representing a transition between the two body plans. The specimen, which has a partial skin impression, has a small caudal fin, a long and narrow body, and a high presacral vertebral count. These features all suggest an anguilliform swimming mode. Later ichthyosaurs retained the high vertebral count, but overcame the high swimming costs of this plesiomorphy, achieving a rigid tunniform bauplan by evolving discoidal vertebrae, and a deep fusiform body. Chensaurus therefore seems to be an evolutionary intermediate between the shorter-bodied terrestrial stock from which the group evolved, and advanced thunniform ichthyosaurs.
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Authors and Affiliations
- Department of Zoology, University of Toronto, Toronto, Ontario, M5S 1A1, Canada
R. Motani & C. McGowan - Department of Paleobiology, Royal Ontario Museum, Toronto, Ontario, M5S 2C6, Canada
R. Motani & C. McGowan - Institute of Vertebrate Paleontology and Paleoanthropology, PO Box 643, Beijing, 100044, China
You H.
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- R. Motani
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Motani, R., H., Y. & McGowan, C. Eel-like swimming in the earliest ichthyosaurs.Nature 382, 347–348 (1996). https://doi.org/10.1038/382347a0
- Received: 25 March 1996
- Accepted: 31 May 1996
- Issue Date: 25 July 1996
- DOI: https://doi.org/10.1038/382347a0