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.

The braincase and jaws of a Devonian ‘acanthodian’ and modern gnathostome origins

Nature volume 457, pages 305–308 (2009)Cite this article

Abstract

Modern gnathostomes (jawed vertebrates) emerged in the early Palaeozoic era1, but this event remains unclear owing to a scant early fossil record. The exclusively Palaeozoic ‘acanthodians’ are possibly the earliest2,3 gnathostome group and exhibit a mosaic of shark- and bony fish-like characters that has long given them prominence in discussions of early gnathostome evolution1. Their relationships with modern gnathostomes have remained mysterious, partly because their un-mineralized endoskeletons rarely fossilized. Here I present the first-known braincase of an Early Devonian (approximately 418–412 Myr bp) acanthodian, Ptomacanthus anglicus4, and re-evaluate the interrelationships of basal gnathostomes. Acanthodian braincases have previously been represented by a single genus, Acanthodes5, which occurs more than 100 million years later in the fossil record. The braincase of Ptomacanthus differs radically from the osteichthyan-like braincase of Acanthodes5 in exhibiting several plesiomorphic features shared with placoderms6,7 and some early chondrichthyans8,9. Most striking is its extremely short sphenoid region and its jaw suspension, which displays features intermediate between some Palaeozoic chondrichthyans and osteichthyans. Phylogenetic analysis resolves Ptomacanthus as either the most basal chondrichthyan or as the sister group of all living gnathostomes. These new data alter earlier conceptions of basal gnathostome phylogeny and thus help to provide a more detailed picture of the acquisition of early gnathostome characters.

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

Relevant articles

Open Access articles citing this article.

Access options

Rent or buy this article

Get just this article for as long as you need it

$39.95

Learn more

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

Figure 1: Ptomacanthus anglicus NHM P 24919a.
Figure 2: Comparison of neurocranial proportions (ventral view) in early gnathostome taxa drawn to same anterior–posterior length.
Figure 3: Results of phylogenetic analyses and selected gnathostome palatoquadrates.

References

  1. Janvier, P. Early Vertebrates (Oxford Univ. Press, 1996)

    Google Scholar 

  2. Smith, M. M. & Sansom, I. J. Exoskeletal micro-remains of an Ordovician fish from the Harding Sandstone of Colorado. Palaeontology 40, 645–658 (1997)

    Google Scholar 

  3. Hanke, G. F. Paucicanthus vanelsti gen. et sp. nov., an Early Devonian (Lochkovian) acanthodian that lacks paired fin-spines. Can. J. Earth Sci. 39, 1071–1083 (2002)

    Article  ADS  Google Scholar 

  4. Miles, R. S. Articulated acanthodian fishes from the Old Red Sandstone of England, with a review of the structure and evolution of the acanthodian shoulder-girdle. Bull. Br. Mus. Nat. Hist. (Geol.) 24, 111–213 (1973)

    Google Scholar 

  5. Miles, R. S. in Interrelationships of Fishes (eds Greenwood, P. H., Miles, R. S. & Patterson, C.) 63–103 (Academic, 1973)

    Google Scholar 

  6. Stensiö, E. Anatomical studies on the arthrodiran head, part I. Kungl. Svensk. Vetenskakad. Handl. 9, 1–419 (1963)

    Google Scholar 

  7. Goujet, D. Les Poissons Placodermes du Spitsberg (Cahiers de Paléontologie, Section Vertébrés, Centre National de la Recherche Scientifique, 1984)

    Google Scholar 

  8. Maisey, J. G. in Major Events in Early Vertebrate Evolution (ed. Ahlberg, P. E.) 263–288 (Taylor and Francis, 2001)

    Google Scholar 

  9. Maisey, J. G. Braincase of the Upper Devonian shark Cladodoides wildungensis (Chondrichthyes, Elasmobranchii), with observations on the braincase in early chondrichthyans. Bull. Am. Mus. Nat. Hist. 288, 1–103 (2005)

    Article  Google Scholar 

  10. Nelson, G. J. Gill arches and the phylogeny of fishes, with notes on the classification of vertebrates. Bull. Am. Mus. Nat. Hist. 141, 475–552 (1969)

    Google Scholar 

  11. Gagnier, P.-Y. & Wilson, M. V. H. Early Devonian acanthodians from northern Canada. Palaeontology 39, 241–258 (1996)

    Google Scholar 

  12. Hanke, G. F. & Wilson, M. V. H. in Recent Advances in the Origin and Early Radiation of Vertebrates (eds Arratia, G., Wilson, M. V. H. & Cloutier, R.) 189–216 (Pfeil, 2004)

    Google Scholar 

  13. Wilson, M. V. H., Hanke, G. F. & Märss, T. in Major Transitions in Vertebrate Evolution (eds Anderson, J. S. & Sues, H.-D.) 122–149 (Indiana Univ. Press, 2007)

    Google Scholar 

  14. Burrow, C. J. & Young, G. C. An articulated teleostome fish from the Late Silurian (Ludlow) of Victoria, Australia. Rec. W. Aust. Mus. Suppl. 57, 1–14 (1999)

    Google Scholar 

  15. Young, G. C. Devonian sharks from south-eastern Australia and Antarctica. Palaeontology 25, 817–843 (1982)

    Google Scholar 

  16. Miller, R. F., Cloutier, R. & Turner, S. The oldest articulated chondrichthyan from the Early Devonian period. Nature 425, 501–504 (2003)

    Article  ADS  CAS  Google Scholar 

  17. Zhu, M., Yu, X. & Janvier, P. A primitive fossil fish sheds light on the origin of bony fishes. Nature 397, 607–610 (1999)

    Article  ADS  CAS  Google Scholar 

  18. Gardiner, B. G. The relationships of the palaeoniscoid fishes, a review based on new specimens of Mimia and Moythomasia from the Upper Devonian of Western Australia. Bull. Br. Mus. Nat. Hist. (Geol.) 37, 173–428 (1984)

    Google Scholar 

  19. Jarvik, E. Basic Structure and Evolution of Vertebrates (Academic, 1980)

    Google Scholar 

  20. Ørvig, T. in Problèmes actuels de Paleontologie: Evolution des Vertébrés (ed. Lehman, J. P.) 41–71 (Colloques Internationaux du Centre National de la Recherche Scientifique, 1975)

    Google Scholar 

  21. Schaeffer, B. The xenacanth shark neurocranium, with comments on elasmobranch monophyly. Bull. Am. Mus. Nat. Hist. 169, 1–66 (1981)

    Google Scholar 

  22. Young, G. C. New information on the structure and relationships of Buchanosteus (Placodermi: Euarthrodira) from the Early Devonian of New South Wales. Zool. J. Linn. Soc. 66, 309–352 (1979)

    Article  Google Scholar 

  23. Basden, A. M., Young, G. C., Coates, M. I. & Ritchie, A. The most primitive osteichthyan braincase? Nature 403, 185–188 (2000)

    Article  ADS  CAS  Google Scholar 

  24. Basden, A. M. & Young, G. C. A primitive actinopterygian neurocranium from the Early Devonian of southeastern Australia. J. Vertebr. Paleontol. 21, 754–766 (2001)

    Article  Google Scholar 

  25. Schaeffer, B. in Problèmes actuels de Paleontologie: Evolution des Vertébrés (ed. Lehman, J. P.) 101–109 (Colloques Internationaux du Centre National de la Recherche Scientifique, 1975)

    Google Scholar 

  26. Maisey, J. G. An evaluation of jaw suspension in sharks. Am. Mus. Novit. 2706, 1–17 (1980)

    Google Scholar 

  27. Schultze, H.-P. & Cumbaa, S. L. in Major Events in Early Vertebrate Evolution (ed. Ahlberg, P. E.) 315–332 (Taylor and Francis, 2001)

    Google Scholar 

  28. Friedman, M. Styloichthys as the oldest coelacanth: implications for early osteichthyan interrelationships. J. Syst. Palaeontol. 5, 289–343 (2007)

    Article  Google Scholar 

  29. Johanson, Z. Vascularization of the osteostracan and antiarch (Placodermi) pectoral fin: similarities, and implications for placoderm relationships. Lethaia 35, 169–186 (2002)

    Article  Google Scholar 

Download references

Acknowledgements

I thank M. Richter for loans of specimens and access to collections; S. Davis, M. Friedman, D. Goujet, J. Long, J. Maisey and G. Young for discussions on early gnathostome endocranial anatomy; P. Ahlberg and H. Blom for discussions and support during all phases of this work. Financial support for this work was provided by a Natural Sciences and Engineering Research Council of Canada Postgraduate Scholarship (NSERC PGS-D 331758-2006) awarded to the author. Thanks to J. Maisey, R. Miller and S. Turner for access to unpublished data on Doliodus.

Author information

Authors and Affiliations

  1. Subdepartment of Evolutionary Organismal Biology, Department of Physiology and Developmental Biology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18A, SE-752 36 Uppsala, Sweden,

    Martin D. Brazeau

Authors
  1. Martin D. Brazeau
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Martin D. Brazeau.

Supplementary information

Supplementary Information

This file contains Supplementary Notes, Supplementary Methods, Supplementary Tables 1-2, Supplementary Figures 1-11 with Legends and Supplementary References (PDF 3689 kb)

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Brazeau, M. The braincase and jaws of a Devonian ‘acanthodian’ and modern gnathostome origins. Nature 457, 305–308 (2009). https://doi.org/10.1038/nature07436

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature07436

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

Advanced 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