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Mandible shape and dwarfism in squirrels (Mammalia, Rodentia): interaction of allometry and adaptation

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Abstract

Squirrels include several independent lineages of dwarf forms distributed into two ecological groups: the dwarf tree and flying squirrels. The mandible of dwarf tree squirrels share a highly reduced coronoid process and a condylar process drawn backwards. Dwarf flying squirrels on the other hand, have an elongated coronoid process and a well-differentiated condylar process. To interpret such a difference, Elliptic Fourier Transform was used to evaluate how mandible shape varies with dwarfism in sciurids. The results obtained show that this clear-cut difference cannot be explained by a simple allometric relationship in relation with size decrease. We concluded that the retention of anteriorly positioned eye sockets, in relation with distance estimation, allowed the conservation of a well-differentiated coronoid process in all flying species, despite the trend towards its reduction observed among sciurids as their size decreases.

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Acknowledgements

We are grateful to Christian Denys, Jacques Cuisin and their collaborators (Museum National d’Histoire Naturelle, Paris) for access to comparative material. We are also indebted to two anonymous reviewers, Andrea Cardini as well as the associated editors for their contribution to improve the manuscript. This is a publication of the Institut des Sciences de l’Evolution de Montpellier (Unité Mixte de Recherche 5554 du Centre National de la Recherche Scientifique) no. 2009-021.

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Authors and Affiliations

  1. Laboratoire de Paléontologie, Institut des Sciences de l’Evolution de Montpellier, UMR-CNRS 5554, Cc 064, Université de Montpellier 2, 2, place Eugène Bataillon, 34095, Montpellier Cedex 5, France

    Lionel Hautier

  2. Laboratoire de Phylogénie Moléculaire, Institut des Sciences de l’Evolution de Montpellier, UMR-CNRS 5554, Cc 064, Université de Montpellier 2, 2, place Eugène Bataillon, 34095, Montpellier Cedex 5, France

    Pierre-Henri Fabre

  3. Laboratoire EPHE de Paléontologie des Vertébrés, et Institut des Sciences de l’Evolution, UMR 5554, CC 064, Université Montpellier 2, Place Eugène Bataillon, 34095, Montpellier Cedex 05, France

    Jacques Michaux

Authors
  1. Lionel Hautier
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  2. Pierre-Henri Fabre
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  3. Jacques Michaux
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Corresponding author

Correspondence to Lionel Hautier.

Electronic supplementary material

Below is the link to the electronic supplementary material.

S1

List of measured specimens; Abbr. abbreviations used in the PCA, N number of specimens measured per species. (JPEG 2984 kb)

S2

Comparisons of allometric trajectories between tribes of FS and NFS, tribes represented by a single genus (i.e. Marmotini, Ratufini and Sciurillini) were not considered; significant values are in italics. (JPEG 1296 kb)

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Hautier, L., Fabre, PH. & Michaux, J. Mandible shape and dwarfism in squirrels (Mammalia, Rodentia): interaction of allometry and adaptation. Naturwissenschaften 96, 725–730 (2009). https://doi.org/10.1007/s00114-009-0519-8

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  • DOI: https://doi.org/10.1007/s00114-009-0519-8

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