Following from Sérgio's departure for working at the European Commission, Lionel took over the wealth of data accumulated during Sérgio's post-doc unfortunately accomplished during COVID-19 lockdown. In collaboration with Helder Gomes Rodrigues from the Natural History Museum Paris, they reconstructed the mandibular canal from CT-scans of both extant and fossil sirenians in order to reconstruct the evolution of tooth loss and replacement by a unique keratinous pad. In parallel, Chris and Frédéric analyzed available genomic data to study the loss of function of tooth genes in extant sirenians but also in the recently extinct Steller's sea cow (Hydrodamalis gigas). The results published in the Proceedings of the Royal Society B (doi:10.1098/rspb.2023.1932) show that by tracing the phylogenetic history of tooth innervation it is possible to understand 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 .
3D models reconstructed from CT-scans of sirenians skulls and mandibles for this project have been made freely available from MorphoMuseuM (doi:10.18563/journal.m3.218).
Finally, Dr. Nicholas D. Pyenson (National Museum of Natural History, Smithsonian Institution, Washington DC, USA) kindly wrote a nice commentary about our paper (doi:10.1098/rspb.2024.1154).
Citations:
Hautier L., Gomes Rodrigues H., Ferreira-Cardoso S., Emerling C.A., Porcher M.-L., Asher R.J., Portela Miguez R. & Delsuc F. (2023). From teeth to pad: tooth loss and development of keratinous structures in sirenians. Proceedings of the Royal Society B 290:20231932. doi:10.1098/rspb.2023.1932
Hautier L., Gomes Rodrigues H., Ferreira-Cardoso S. & Delsuc F. (2023). 3D models related to the publication: From teeth to pad, tooth loss and development of keratinous structures in sirenians. MorphoMuseuM 9:e218. doi:10.18563/journal.m3.218
Commentary:
Pyenson N.D. (2024). How teeth, tusks and horny pads evolved together in sea cows. Proceedings of the Royal Society B 291:20241154. doi:10.1098/rspb.2024.1154
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