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Intraspecific Variation of Endocranial Structures in Extant Equus: A Prelude to Endocranial Studies in Fossil Equoids

Endocranial Intraspecific Variation in Equus

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Abstract

Intraspecific variation of endocranial structures is not widely studied in most mammals, particularly fossil mammals, which are mainly represented by a few preserved crania. However, a description of this variation is necessary to be able to study fossil mammals from an ecological and phylogenetic perspective. To facilitate further analyses on fossil equoids, digital reconstructions of the cranial endocast, petrosal bone, and bony labyrinth were created based on CT scans, taken from a wild population of 12 Equus caballus przewalskii currently being monitored. Using descriptive, biometric, and morphometric analyses, an unsuspected range of intraspecific variation for 40 endocranial characters is revealed. Intraindividual variation can be further understood through the comparison of paired organs from a single individual. These results prompt cautious consideration of these characters, as well as an index for the determination of hearing abilities or encephalization quotients.

Thanks to this work, more is now known about the intraspecific variation of the external morphology of the most frequently studied structures in the endocranium of mammals and more specifically in equoids, where no such study had been undertaken until now. This will help to improve the resolution of fossil endocranial studies.

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Acknowledgments

First, we want to thank Claudia Feh and the TAKH association for the gracious loan of all the Przewalski skulls studied in this work and all information about the life of these individuals. CT scans of the Przewalski’s horses have been possible with the assistance of the CHU Lapeyronie (Montpellier), which provided the tomograph and the technicians. To scan the two freshly cut horse heads, we also appealed to a veterinarian, Laure Poujol (veterinary clinic of Celleneuve, Montpellier), for whose help we are grateful. We are very grateful to Renaud Lebrun from the University of Montpellier who trained one of us (LD) in the use of morphometric software. Finally, we thank the two anonymous reviewers who contributed to improving the manuscript. This work has been supported by the ANR funding project Palasiafrica. This is the publication ISEM n° 2015–051.

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  1. Institut des Sciences de l’Evolution de Montpellier (ISEM) – UMR CNRS 5554, Université de Montpellier, CNRS, IRD, EPHE, Place Eugène Bataillon, FR–34095, Montpellier cedex 05, France

    Laure Danilo, Monique Vianey-Liaud & Fabrice Lihoreau

  2. 46 rue Rouget de Lisle, 30000, Nimes, France

    Jean Remy

  3. Centre de Radiologie, Clinique du Parc, Castelnau Le Lez, France

    Samuel Mérigeaud

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  1. Laure Danilo
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Correspondence to Laure Danilo.

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Danilo, L., Remy, J., Vianey-Liaud, M. et al. Intraspecific Variation of Endocranial Structures in Extant Equus: A Prelude to Endocranial Studies in Fossil Equoids. J Mammal Evol 22, 561–582 (2015). https://doi.org/10.1007/s10914-015-9293-x

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