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.

Triassic marine reptiles gave birth to live young


Sauropterygians form the largest and most diverse group of ancient marine reptiles that lived throughout nearly the entire Mesozoic era (from 250 to 65 million years ago)1,2. Although thousands of specimens of this group have been collected around the world since the description of the first plesiosaur in 1821 (ref. 3), no direct evidence has been found to determine whether any sauropterygians came on shore to lay eggs (oviparity) like sea turtles, or gave birth in the water to live young (viviparity) as ichthyosaurs and mosasauroids (marine lizards) did4,5,6. Viviparity has been proposed for plesiosaur, pachypleurosaur and nothosaur sauropterygians7,8,9,10, but until now no concrete evidence has been advanced. Here we report two gravid specimens of Keichousaurus hui Young from the Middle Triassic of China. These exquisitely preserved specimens not only provide the first unequivocal evidence of reproductive mode and sexual dimorphism in sauropterygians, but also indicate that viviparity could have been expedited by the evolution of a movable pelvis in pachypleurosaurs. By extension, this has implications for the reproductive pattern of other sauropterygians and Mesozoic marine reptiles that possessed a movable pelvis.

This is a preview of subscription content

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Two gravid specimens of Keichousaurus hui in dorsal view.
Figure 2: The trunk region of NMNS-cyn2002-01 in dorsal view.
Figure 3
Figure 4: Sacral vertebrae and pelvis of selected sauropterygians.


  1. Carroll, R. L. Vertebrate Paleontology and Evolution (Freeman, New York, 1988)

    Google Scholar 

  2. Rieppel, O. Encyclopedia of Paleoherpetology Vol. 12A 1–134 (Verlag Dr Friedrich Pfeil, Munich, 2000)

    Google Scholar 

  3. Taylor, M. A. in Ancient Marine Reptiles (eds Callaway, J. M. & Nicholls, E. L.) xix–xlvi (Academic, San Diego, 1997)

    Google Scholar 

  4. Johnson, R. Size independent criteria for estimating relative age and the relationships among growth parameters in a group of fossil reptiles (Reptilia, Ichthyosauria). Can. J. Earth Sci. 14, 1916–1924 (1977)

    ADS  Google Scholar 

  5. Benton, M. J. The myth of the Mesozoic cannibals. New Sci. 12, 40–44 (1991)

    Google Scholar 

  6. Caldwell, M. W. & Lee, M. S. Y. Live birth in Cretaceous marine lizards (mosasauroids). Proc. R. Soc. Lond. B 268, 2397–2401 (2001)

    CAS  Google Scholar 

  7. Taylor, M. A. Lifestyle of plesiosaurs. Nature 319, 179 (1986)

    ADS  Google Scholar 

  8. Sander, P. M. The pachypleurosaurids (Reptilia: Nothosauria) from the Middle Triassic of Monte San Giorgio (Switzerland), with the description of a new species. Phil. Trans. R. Soc. Lond. B 325, 561–670 (1989)

    ADS  CAS  Google Scholar 

  9. Lin, K. & Rieppel, O. Functional morphology and ontogeny of Keichousaurus hui (Reptilia, Sauropterygia). Fieldiana (Geol.) 39, 1–35 (1998)

    CAS  Google Scholar 

  10. Renesto, S., Lombardo, C., Tintori, A. & Danini, G. Nothosaurid embryos from the Middle Triassic of northern Italy: an insight into the viviparity of nothosaurs? J. Vert. Paleontol 23, 957–960 (2003)

    Google Scholar 

  11. Wang, L. et al. Biostratigraphy of Triassic marine reptiles in southwest Guizhou and its adjacent area. Acta Geol. Sinica 74, 349–353 (2001)

    Google Scholar 

  12. Böttcher, R. Neue Erkenntnisse über die Fortpflanzungs-biologie der Ichthyosaurier (Reptilia). Stuttgarter Beitr. Naturk. B 164, 1–51 (1990)

    Google Scholar 

  13. Fox, H. in Biology of the Reptilia (ed. Gans, C.) 1–122 (Academic, London, 1977)

    Google Scholar 

  14. Deeming, D. C., Halstead, L. B., Manabe, M. & Unwin, D. M. An ichthyosaur embryo from the Lower Lias (Jurassic: Hettangian) of Somerset, England, with comments on the reproductive biology of ichthyosaurs. Mod. Geol. 18, 423–442 (1993)

    Google Scholar 

  15. Rieppel, O. A new pachypleurosaur (Reptilia: Sauropterygia) from the Middle Triassic of Monte San Giorgio, Switzerland. Phil. Trans. R. Soc. Lond. B 323, 1–73 (1989)

    ADS  Google Scholar 

  16. Carroll, R. L. & Gaskill, P. The nothosaur Pachypleurosaurus and the origin of plesiosaurs. Phil. Trans. R. Soc. Lond. B 309, 343–393 (1985)

    ADS  Google Scholar 

  17. Sues, H.-D. & Carroll, R. L. The pachypleurosaurid Dactylosaurus schroederi (Diapsida: Sauropterygia). Can. J. Earth Sci. 22, 1602–1608 (1985)

    ADS  Google Scholar 

  18. Rieppel, O. The status of the sauropterygian reptile genera Ceresiosaurus, Lariosaurus, and Silvestrosaurus from the Middle Triassic of Europe. Fieldiana 38, 1–46 (1998)

    Google Scholar 

  19. Rieppel, O., Li, J. & Liu, J. Lariosaurus xingyiensis (Reptilia: Sauropterygia) from the Triassic of China. Can. J. Earth Sci. 40, 621–634 (2003)

    ADS  Google Scholar 

  20. Brown, D. S. The English Upper Jurassic Plesiosauroidea (Reptilia) and a review of the phylogeny and classification of the Plesiosauria. Bull. Br. Mus. Nat. Hist. (Geol.) 35, 253–347 (1981)

    Google Scholar 

  21. Bardet, N., Godefroit, P. & Sciau, J. A new elasmosaurid plesiosaur from the Lower Jurassic of southern France. Palaeontology 42, 927–952 (1999)

    Google Scholar 

  22. Sato, T. Terminonatator ponteixensis, a new elasmosaur (Reptilia: Sauropterygia) from the Upper Cretaceous of Saskatchewan. J. Vert. Paleontol. 23, 89–103 (2003)

    Google Scholar 

  23. Andrews, C. W. A Descriptive Catalogue of the Marine Reptiles of the Oxford Clay, Part I (Br. Mus. Nat. Hist., London, 1910)

    Google Scholar 

  24. Sues, H.-D. Postcranial skeleton of Pistosaurus and interrelationships of the Sauropterygia (Diapsida). Zool. J. Linn. Soc. 90, 109–131 (1987)

    Google Scholar 

  25. Sato, T., Li, C. & Wu, X.-C. Restudy of Bishanopliosaurus youngi Dong 1980, a freshwater plesiosaurian from the Jurassic of Chongqing, China. Vertebrata PalAsiatica 41, 33–47 (2003)

    Google Scholar 

Download references


We thank R. Holmes and T. Sato of the Canadian Museum of Nature (CMN), Ottawa, for advice, suggestions and access to their reference collections, and R. Holmes for reading earlier drafts and for editorial assistance. X.-c. W. was supported by research grants from the CMN.

Author information

Authors and Affiliations


Corresponding authors

Correspondence to Yen-nien Cheng or Xiao-chun Wu.

Ethics declarations

Competing interests

The authors declare that they have no competing financial interests.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Cheng, Yn., Wu, Xc. & Ji, Q. Triassic marine reptiles gave birth to live young. Nature 432, 383–386 (2004).

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI:

Further reading


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