Proceedings of the Royal Society B: Biological Sciences
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From teeth to pad: tooth loss and development of keratinous structures in sirenians

Lionel Hautier

Lionel Hautier

Institut des Sciences de l’Évolution, Université Montpellier, CNRS, IRD, EPHE, Montpellier 34095, France

Mammal Section, Life Sciences, Vertebrate Division, The Natural History Museum, London, UK

[email protected]

Contribution: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing

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Helder Gomes Rodrigues

Helder Gomes Rodrigues

Centre de Recherche en Paléontologie—Paris (CR2P), UMR CNRS 7207, Muséum National d'Histoire Naturelle, Sorbonne Université, Paris, France

Contribution: Conceptualization, Funding acquisition, Investigation, Supervision, Validation, Writing – review & editing

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Sérgio Ferreira-Cardoso

Sérgio Ferreira-Cardoso

Institut des Sciences de l’Évolution, Université Montpellier, CNRS, IRD, EPHE, Montpellier 34095, France

Contribution: Conceptualization, Formal analysis, Funding acquisition, Investigation, Validation, Visualization, Writing – review & editing

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Christopher A. Emerling

Christopher A. Emerling

Biology Department, Reedley College, Reedley, CA 93654, USA

Contribution: Conceptualization, Formal analysis, Investigation, Methodology, Software, Validation, Visualization, Writing – review & editing

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Marie-Lou Porcher

Marie-Lou Porcher

Institut des Sciences de l’Évolution, Université Montpellier, CNRS, IRD, EPHE, Montpellier 34095, France

Contribution: Formal analysis, Visualization

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Robert J. Asher

Robert J. Asher

Department of Zoology, University of Cambridge, Cambridge, UK

Contribution: Data curation, Validation, Writing – review & editing

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Roberto Portela Miguez

Roberto Portela Miguez

Mammal Section, Life Sciences, Vertebrate Division, The Natural History Museum, London, UK

Contribution: Data curation, Validation, Writing – review & editing

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Frédéric Delsuc

Frédéric Delsuc

Institut des Sciences de l’Évolution, Université Montpellier, CNRS, IRD, EPHE, Montpellier 34095, France

Contribution: Conceptualization, Formal analysis, Funding acquisition, Investigation, Methodology, Software, Supervision, Validation, Writing – review & editing

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Published:https://doi.org/10.1098/rspb.2023.1932

    Sirenians are a well-known example of morphological adaptation to a shallow-water grazing diet characterized by a modified feeding apparatus and orofacial morphology. Such adaptations were accompanied by an anterior tooth reduction associated with the development of keratinized pads, the evolution of which remains elusive. Among sirenians, the recently extinct Steller's sea cow represents a special case for being completely toothless. Here, we used μ-CT scans of sirenian crania to understand how motor-sensor systems associated with tooth innervation responded to innovations such as keratinized pads and continuous dental replacement. In addition, we surveyed nine genes associated with dental reduction for signatures of loss of function. Our results reveal how patterns of innervation changed with modifications of the dental formula, especially continuous replacement in manatees. Both our morphological and genomic data show that dental development was not completely lost in the edentulous Steller's sea cows. By tracing the phylogenetic history of tooth innervation, we illustrate the role of development in promoting the innervation of keratinized pads, similar to the secondary use of dental canals for innervating neomorphic keratinized structures in other tetrapod groups.

    Footnotes

    Electronic supplementary material is available online at https://doi.org/10.6084/m9.figshare.c.6927574.

    References