Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Eel-like swimming in the earliest ichthyosaurs


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.

This is a preview of subscription content, access via your institution

Access options

Rent or buy this article

Prices vary by article type



Prices may be subject to local taxes which are calculated during checkout


  1. Massare, J. A. & Callaway, J. M. Geol. Soc. Am. Bull. 102, 409–416 (1990).

    Article  ADS  Google Scholar 

  2. Baird, D. Mosasur 2, 129–133 (1984).

    Google Scholar 

  3. Callaway, J. M. & Massare, J. A. Neues Jb. Geol. Palaont Mh. 178, 37–58 (1989).

    Google Scholar 

  4. Carroll, R. L. Spec. Pap. Palaeont. 33, 145–155 (1985).

    Google Scholar 

  5. Chen, L.-Z. Reg. Geol. China 15, 139–146 (1985).

    Google Scholar 

  6. Mazin, J.-M., Suteethom, V., Buffetaut, E., Jaeger, J.-J. & Helmcke-Ingavat, R. C. r. hebd. Séanc. Acad. Sci., Paris 313, 1207–1212 (1991).

    Google Scholar 

  7. Wang, G. X. Marine Facies of Triassic System of Anhui 1–73 (Anhui Science and Technology, Hefei, 1984).

    Google Scholar 

  8. McGowan, C. Palaeontology 35, 555–570 (1992).

    Google Scholar 

  9. Webb, P. W. & Blake, R. W. in Functional Vertebrate Morphology (eds Hildebrand, M., Bramble, D. M., Liem, K. F. & Wake, D. B.) 110–128 (Harvard Univ. Press, Cambridge, MA, 1985).

    Google Scholar 

  10. Webb, P. W. & Keyes, R. S. Fish. Bull. F.A.O. 89, 803–812 (1982).

    ADS  Google Scholar 

  11. Thomson, K. S. & Simanek, D. E. Am. Zool. 17, 343–354 (1977).

    Article  Google Scholar 

  12. Webb, P. W. Am. Zool. 28, 709–725 (1988).

    Article  Google Scholar 

  13. Massare, J. A. Paleobiology 14, 187–205 (1988).

    Article  Google Scholar 

  14. Romer, A. S. The Osteology of the Reptiles 1–772 (Univ. Chicago Press, 1956).

    Google Scholar 

  15. Hoffstetter, R. & Gasc, J.-P. in Biology of the Reptilia Vol. 1 (eds Gans, C., Bellairs, A. d'A. & Parsons, T. S.) 201–310 (Academic, New York, 1969).

    Google Scholar 

  16. McGowan, C. Life Sci. Contr. R. Ont. Mus. 97, 1–37 (1974).

    Google Scholar 

  17. McGowan, C. Life Sci. Contr. R. Ont. Mus. 100, 1–30 (1974).

    Google Scholar 

  18. McGowan, C. Palaeontogr. am. A166, 93–135 (1979).

    Google Scholar 

  19. Merriam, J. C. Mem. Univ. Calif. 1, 1–196 (1908).

    Google Scholar 

  20. Kosch, B. F. J. Vertebr. Paleontol. 10, 512–514 (1990).

    Article  Google Scholar 

  21. Riess, J. Palaeontogr. am. A192, 93–155 (1986).

    Google Scholar 

  22. Springer, V. G. & Garrick, J. A. F. Proc. U.S. natn. Mus. 116, 73–96 (1964).

    Article  Google Scholar 

  23. Kuhn-Schnyder, E. Neujahrsblatt, Die Triasfauna der Tessiner Kalkalpen 1–119 (Natur-forschenden Gesselschaft, Zurich, 1974).

    Google Scholar 

  24. Last, P. R. & Stevens, J. D. Sharks and Rays of Australia 1–513 (CSIRO Australia, 1994).

    Google Scholar 

  25. Hauff, B. & Hauff, R. B. Das Holzmadenbuch 1–136 (Repro-Druck, Fellbach, 1981).

    Google Scholar 

Download references

Author information

Authors and Affiliations


Rights and permissions

Reprints and permissions

About this article

Cite this article

Motani, R., H., Y. & McGowan, C. Eel-like swimming in the earliest ichthyosaurs. Nature 382, 347–348 (1996).

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI:

This article is cited by


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing