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Palaeospondylus and the early evolution of gnathostomes

Nature volume 620, pages E20–E22 (2023)Cite this article

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Matters Arising to this article was published on 23 August 2023

The Original Article was published on 25 May 2022

arising from: T. Hirasawa et al. Nature https://doi.org/10.1038/s41586-022-04781-3 (2022)

The first quarter of the twenty-first century has seen a revolution in our understanding of the early evolution of tetrapods, ignited by the recovery of multiple exceptional fossils from the Devonian1,2. The transition from water to land at the tetrapod stem involved numerous changes to the skeleton, particularly the skull, shoulder girdle and forelimb, for life in the terrestrial realm1,2,3. †Palaeospondylus gunni is a Middle Devonian vertebrate from Scotland whose affinities to other vertebrates have remained controversial over more than 130 years of study4; in the past two decades, †P. gunni has variously been considered a relative of hagfishes5,6, a larval lungfish7, an early member of the shark and ray total clade, or an intermediate jawed vertebrate5 (note that extinct species are indicated by a dagger). Here I re-evaluate the recently hypothesized pan-tetrapod identity of †P. gunni proposed by Hirasawa et al.4 and show that †P. gunni is a gnathostome of unclear affinities to the major crown clades.

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Fig. 1: Relationships of †P. gunni resolved in phylogenetic analyses of parsimony.
Fig. 2: The evolutionary relationships and divergence times of early jawed vertebrates.

Data availability

All data are available in the Supplementary Information attached to this article.

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Acknowledgements

I thank the Willi Hennig society for funding TNT v.1.5. Silhouettes in Figs. 1 and 2 are in the public domain from PhyloPic (www.phylopic.org). I thank the authors of the original study for granting me access to the computed tomography scan data.

Author information

Authors and Affiliations

  1. Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, USA

    Chase Doran Brownstein

  2. Stamford Museum and Nature Center, Stamford, CT, USA

    Chase Doran Brownstein

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  1. Chase Doran Brownstein
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Contributions

C.D.B. designed the experiments, analysed the data and wrote the manuscript.

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Correspondence to Chase Doran Brownstein.

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The author declares no competing interests.

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Supplementary information

Supplementary Information

This file contains Supplementary Methods, Justifications of codings for †Palaeospondylus gunni, and Supplementary References.

Reporting Summary

Supplementary Figures

This file contains Supplementary Figures 1 and 2. Supplementary Figure 1: Expanded trees from the parsimony analysis of the original dataset. (a) Strict consensus and (b) combinable consensus trees. Supplementary Figure 2. Expanded tree from the Bayesian analysis of the original dataset: (a) Maximum clade credibility tree. Blue bars indicate 95% confidence intervals for node ages. MYA = millions of years ago.

Supplementary Data 1

Source Data for Figure 1: Parsimony analysis data and output.

Supplementary Data 2

Source Data for Figure 2: Bayesian analysis data and output.

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Brownstein, C.D. Palaeospondylus and the early evolution of gnathostomes. Nature 620, E20–E22 (2023). https://doi.org/10.1038/s41586-023-06434-5

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