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Xenacoelomorpha, a Key Group to Understand Bilaterian Evolution: Morphological and Molecular Perspectives

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Evolution, Origin of Life, Concepts and Methods

Abstract

The Xenacoelomorpha is a clade of mostly marine animals placed as the sister group of the remaining Bilateria (Nephrozoa) in most phylogenomic and morphological analyses, although alternative hypotheses placing them within deuterostomes have been proposed. This key phylogenetic position has raised recently a great interest in the study of their constitutive clades, since they can provide us with character states that illuminate different aspects of the origin of bilateral animals. Moreover, the recent availability of genomic and transcriptomic data from different species has been used in inferring the internal relationships among xenacoelomorph clades and the deciphering of molecular mechanisms that contribute to the evolution of metazoan genomes. Having access to molecular data paves the way to the systematic analysis of the genetic control of xenacoelomorph development and, additionally, to a better-informed study of bilaterian innovations. Here we revisit what has been learned over the last decades on the morphology, genomics and phylogenetic relationships of the Xenacoelomorpha.

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Acknowledgements

Funding from The Swedish Research Council (project 2018-05191) is gratefully acknowledged by Ulf Jondelius. The work of Olga Raikova was supported by the Ministry of Education and Science of the Russian Federation (project no. AAAA-A19-119020690076-7) and the RFBR (project numbers 16-04-00593a and 20-04-01006a). We would also like to thank Dr. Pierre Pontarotti (Marseille) for organizing the yearly “Evolutionary Biology Meeting” in Marseille and for inviting us to submit this chapter.

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Authors and Affiliations

  1. Swedish Museum of Natural History, Box 50007, 104 05, Stockholm, Sweden

    Ulf Jondelius

  2. Department of Zoology, Stockholm University, Svante Ahrrenius Väg 18b, 106 91, Stockholm, Sweden

    Ulf Jondelius

  3. Zoological Institute RAS, Universitetskaya emb. 1, 199034, St. Petersburg, Russia

    Olga I. Raikova

  4. Faculty of Biology, Chair of Invertebrate Zoology, St. Petersburg State University, Universitetskaya emb. 7/9, 199034, St. Petersburg, Russia

    Olga I. Raikova

  5. Department de Genètica, Microbiologia i Estadística, Universitat de Barcelona, Av. Diagonal, 645, 08028, Barcelona, Spain

    Pedro Martinez

  6. ICREA (Institut Català de Recerca i Estudis Avancats), Barcelona, Spain

    Pedro Martinez

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  1. Ulf Jondelius
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  2. Olga I. Raikova
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  3. Pedro Martinez
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Corresponding authors

Correspondence to Ulf Jondelius , Olga I. Raikova or Pedro Martinez .

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  1. CNRS and IHU, Aix-Marseille University, Marseille, France

    Pierre Pontarotti

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Jondelius, U., Raikova, O.I., Martinez, P. (2019). Xenacoelomorpha, a Key Group to Understand Bilaterian Evolution: Morphological and Molecular Perspectives. In: Pontarotti, P. (eds) Evolution, Origin of Life, Concepts and Methods. Springer, Cham. https://doi.org/10.1007/978-3-030-30363-1_14

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