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The deuterostome context of chordate origins

Abstract

Our understanding of vertebrate origins is powerfully informed by comparative morphology, embryology and genomics of chordates, hemichordates and echinoderms, which together make up the deuterostome clade. Striking body-plan differences among these phyla have historically hindered the identification of ancestral morphological features, but recent progress in molecular genetics and embryology has revealed deep similarities in body-axis formation and organization across deuterostomes, at stages before morphological differences develop. These developmental genetic features, along with robust support of pharyngeal gill slits as a shared deuterostome character, provide the foundation for the emergence of chordates.

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Figure 1: Deuterostome phylogeny.
Figure 2: Key anatomical features of the enteropneust body plan.
Figure 3: A conserved molecular network for the deuterostome anteroposterior axis.
Figure 4: Comparison of the dorsoventral patterning mechanisms of hemichordates and chordates.

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Acknowledgements

We thank K. Bertsche (http://wanderingfalcon.com), for the scientific illustrations, C. Patton and J. Watanabe for photography of invertebrate micrographs, K. Halanych and J. Cannon for providing pterobranch images, and J. Fritzenwanker for the German translation of Grobben, and helpful discussions. We apologize to authors whose work we were unable to cite due to space limitations, and thank M. Kirschner, A. Pani, T. Lacalli, N. Satoh and N. Holland for discussions that helped formulate these ideas. Support for this work was awarded to C.J.L from NASA (NNX13AI68G) and NSF (1258169), to D.M.M. from NSF (IOS1257040). D.S.R. is supported by the Okinawa Institute of Science and Technology and the US National Institutes of Heath through grant R01 GM086321. Work at the Joint Genome Institute is supported by the Office of Science of the US Department of Energy under contract number DE-AC02-05CH11231.

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Lowe, C., Clarke, D., Medeiros, D. et al. The deuterostome context of chordate origins. Nature 520, 456–465 (2015). https://doi.org/10.1038/nature14434

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