The olfactory bulb endocast as a proxy for mammalian olfaction

Olfaction is a critical sense for tetrapods, playing a key role in survival and reproduction by aiding in food detection, predator avoidance, and social interactions. Olfactory performance has been experimentally tested in only a few taxa, so comparative analyses rely on anatomical and genomic proxies. Among anatomical proxies, the olfactory bulb endocast is widely used, particularly in extinct species, where it is often the only preserved proxy and can be reconstructed even in million-year-old fossils. While the functional significance of chemoreceptor genes has received attention, the extent to which the olfactory bulb endocast correlates with genomic proxies remains unclear. Using brain endocasts across all mammalian orders, we investigated the relationship between the absolute (absOB) and relative (relatOB) volumes of the olfactory bulb endocast and the number of intact chemoreceptor genes. While no clear correlations were found between absOB and the genomic proxies tested, we identified a significant correlation between relatOB and the total number of combined intact chemoreceptor genes (CombChemo), primarily driven by olfactory receptor genes (OR). Leveraging this correlation, and aiming to infer olfactory capabilities in taxa for which only the skull is available, we estimated OR numbers for three mammalian orders lacking genomic data, as well as for five extinct mammals. Building on studies that have established a link between intact OR and olfactory sensitivity and discrimination, we conclude that relatOB enables inference of olfactory capabilities in mammals. This provides a basis to investigate sensory evolution and opens perspectives for interpreting paleoecology and behavior of extinct mammals.

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Publication Details

Journal
Proceedings of the National Academy of Sciences
Published
2025-12-08
DOI
https://doi.org/10.1073/pnas.2510575122
Citations
1
Primary Topic
Olfactory and Sensory Function Studies
Type
article
Field-Weighted Citation Impact
1.46
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article

The olfactory bulb endocast as a proxy for mammalian olfaction

Quentin Martinez, Eli Amson, M. S. Zubér, Cécile Molinier et al.
1 citations
Proceedings of the National Academy of Sciences
Olfactory and Sensory Function Studies
1.46
article

The olfactory bulb endocast as a proxy for mammalian olfaction

Quentin Martinez, Eli Amson, M. S. Zubér, Cécile Molinier, Elias Hamann, Kévin Le Verger, Guillaume Billet, Ilse K. Barraza-Soltero, Lionel Hautier, Roberto Portela Miguez, Gabriel S. Ferreira, Thomas van de Kamp, Vincent Fernández, Anne‐Claire Fabre, Éric Berger
article en
1 citations

Abstract

Olfaction is a critical sense for tetrapods, playing a key role in survival and reproduction by aiding in food detection, predator avoidance, and social interactions. Olfactory performance has been experimentally tested in only a few taxa, so comparative analyses rely on anatomical and genomic proxies. Among anatomical proxies, the olfactory bulb endocast is widely used, particularly in extinct species, where it is often the only preserved proxy and can be reconstructed even in million-year-old fossils. While the functional significance of chemoreceptor genes has received attention, the extent to which the olfactory bulb endocast correlates with genomic proxies remains unclear. Using brain endocasts across all mammalian orders, we investigated the relationship between the absolute (absOB) and relative (relatOB) volumes of the olfactory bulb endocast and the number of intact chemoreceptor genes. While no clear correlations were found between absOB and the genomic proxies tested, we identified a significant correlation between relatOB and the total number of combined intact chemoreceptor genes (CombChemo), primarily driven by olfactory receptor genes (OR). Leveraging this correlation, and aiming to infer olfactory capabilities in taxa for which only the skull is available, we estimated OR numbers for three mammalian orders lacking genomic data, as well as for five extinct mammals. Building on studies that have established a link between intact OR and olfactory sensitivity and discrimination, we conclude that relatOB enables inference of olfactory capabilities in mammals. This provides a basis to investigate sensory evolution and opens perspectives for interpreting paleoecology and behavior of extinct mammals.

Proceedings of the National Academy of SciencesVol. 122(50)
Karlsruhe Institute of Technology (DE), University of Bern (CH), Natural History Museum Vienna (AT), Centre National de la Recherche Scientifique (FR), Museum für Naturkunde (DE), Natural History Museum (GB), American Museum of Natural History (US), Université de Montpellier (FR), University of Zurich (CH), European Synchrotron Radiation Facility (FR), Sorbonne Université (FR), Senckenberg Centre for Human Evolution and Palaeoenvironment (DE), Natural History Museum of Bern (CH), Institut des Sciences de l'Evolution de Montpellier (FR), Max Planck Institute for Developmental Biology (DE), Muséum national d'Histoire naturelle (FR), Institut de Paléontologie Humaine (FR), National Synchrotron Radiation Laboratory (CN), Max Planck Institute for Biology (DE), Institut de Recherche pour le Développement (FR), Centre de recherche en paléontologie - Paris (FR), University of Tübingen (DE)
Openalex Percentile: Top 15%
Olfactory and Sensory Function Studies
1.46
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