Skip to main content

Thank you for visiting nature.com. 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.

  • Letter
  • Published:

The axial skeleton of the Devonian tetrapod Ichthyostega

Abstract

Ichthyostega was the first Devonian tetrapod to be subject to a whole-body reconstruction1,2,3. It remains, together with Acanthostega4, one of only two Devonian tetrapods for which near-complete postcranial material is available. It is thus crucially important for our understanding of the earliest stages of tetrapod evolution and terrestrialization. Here we show a new reconstruction of Ichthyostega based on extensive re-examination of original material and augmented by recently collected specimens. Our reconstruction differs substantially from those previously published and reveals hitherto unrecognized regionalization in the vertebral column. Ichthyostega is the earliest vertebrate to show obvious adaptations for non-swimming locomotion. Uniquely among early tetrapods, the presacral vertebral column shows pronounced regionalization of neural arch morphology, suggesting that it was adapted for dorsoventral rather than lateral flexion.

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

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

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

Figure 1: Reconstructions of Ichthyostega and Acanthostega.
Figure 2: Specimens of Ichthyostega.
Figure 3: MGUH VP 6054, vertebral column, pelvis and hindlimb of Ichthyostega.
Figure 4: MGUH VP 6139, skull, shoulder girdle, thoracic and presacral region of Ichthyostega.

Similar content being viewed by others

References

  1. Jarvik, E. On the fish-like tail in the ichthyostegid stegocephalians. Meddelelser øm Grønland 114, 1–90 (1952)

    Google Scholar 

  2. Jarvik, E. The oldest tetrapods and their forerunners. Sci. Mon. 80, 141–154 (1955)

    ADS  Google Scholar 

  3. Jarvik, E. Basic Structure and Evolution of Vertebrates Vol. 1 (Academic, New York, 1980)

    Google Scholar 

  4. Coates, M. I. The Devonian tetrapod Acanthostega gunnari Jarvik: postcranial anatomy, basal tetrapod relationships and patterns of skeletal evolution. Trans. R. Soc. Edinb. Earth Sci. 87, 363–421 (1996)

    Article  Google Scholar 

  5. Jarvik, E. The Devonian tetrapod Ichthyostega. Fossils and Strata 40, 1–206 (1996)

    Google Scholar 

  6. Coates, M. I. & Clack, J. A. in Studies on Early Vertebrates (eds Arsenault, M., Lelièvre, H. & Janvier, P.) 373–388 (Bulletin du Muséum national d'histoire naturelle, Paris, 1995)

    Google Scholar 

  7. Coates, M. I. & Clack, J. A. Polydactyly in the earliest known tetrapod limbs. Nature 347, 66–69 (1990)

    Article  ADS  Google Scholar 

  8. Clack, J. A., Blom, H. & Ahlberg, P. E. New insights into the postcranial skeleton of Ichthyostega. J. Vert. Paleontol. Abstr. 23, 41A (2003)

    Google Scholar 

  9. Blom, H., Clack, J. A. & Ahlberg, P. E. Localities, distribution and stratigraphical context of the Late Devonian tetrapods of East Greenland. Meddelelser øm Grønland Geosci. 43, 4–50 (2005)

    Google Scholar 

  10. Clack, J. A. et al. A uniquely specialised ear in a very early tetrapod. Nature 425, 65–69 (2003)

    Article  ADS  CAS  Google Scholar 

  11. Clack, J. A. An early tetrapod from Romer's Gap. Nature 418, 72–76 (2002)

    Article  ADS  CAS  Google Scholar 

  12. Lombard, R. E. & Bolt, J. R. A new primitive tetrapod, Whatcheeria deltae, from the Lower Carboniferous of Iowa. Palaeontology 38, 471–494 (1995)

    Google Scholar 

  13. Clack, J. A. & Finney, S. M. Pederpes finneyae, an articulated tetrapod from the Tournaisian of western Scotland. J. Syst. Palaeontol. 2, 311–346 (2005)

    Article  Google Scholar 

  14. Ruta, M., Coates, M. I. & Quicke, D. L. J. Early tetrapod relationships revisited. Biol. Rev. 78, 251–345 (2003)

    Article  Google Scholar 

  15. Holmes, R. The Carboniferous amphibian Proterogyrinus scheeli Romer, and the early evolution of tetrapods. Phil. Trans. R. Soc. Lond. B 306, 431–524 (1984)

    Article  ADS  Google Scholar 

  16. Clack, J. A. The dermal skull roof of Acanthostega, an early tetrapod from the Late Devonian. Trans. R. Soc. Edinb. 93, 17–33 (2002)

    Article  Google Scholar 

Download references

Acknowledgements

We thank the Geological Museum and University of Copenhagen for access to their Ichthyostega material, and G. Cuny and D. Harper for their help and support during our visits. We would also like to acknowledge the late E. Jarvik and S. Bendix-Almgreen, both of whom gave us access to specimens then in their care. Preparation of MGUH f.n. 300 was carried out by S. Finney. M. Coates kindly permitted us to use one of his unpublished Acanthostega reconstructions for part of Fig. 1c. Most of our project was supported by an NERC grant with additional funding for H.B. provided by the Isaac Newton Trust Fund and by a project grant and salary from Vetenskapsrådet (the Swedish Research Council) for P.E.A.

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Per Erik Ahlberg.

Ethics declarations

Competing interests

Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.

Supplementary information

Supplementary Notes

Discussion on preservation and taphonomy of the Ichthyostega material. (DOC 30 kb)

Supplementary Figure Legend

Text to accompany Supplementary Figure S1. (DOC 27 kb)

Supplementary Figure S1

This illustrates three thoracic and three lumbar neural arches from different Ichthyostega specimens. (JPG 124 kb)

Rights and permissions

Reprints and permissions

About this article

Cite this article

Ahlberg, P., Clack, J. & Blom, H. The axial skeleton of the Devonian tetrapod Ichthyostega. Nature 437, 137–140 (2005). https://doi.org/10.1038/nature03893

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature03893

This article is cited by

Comments

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.

Search

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