Stable isotope study of a new chondrichthyan fauna (Kimmeridgian, Porrentruy, Swiss Jura): an unusual freshwater-influenced isotopic composition for the hybodont shark Asteracanthus
- Leuzinger, Léa Département des Géosciences, Université de Fribourg, Switzerland - Section d'archéologie et paléontologie, Office de la culture, Porrentruy, Switzerland - CRILAR, 5301 Anillaco, La Rioja, Argentina
- Kocsis, L. Institut des Dynamiques de la Surface Terrestre, Université de Lausanne, Switzerland - Universiti Brunei Darussalam, Faculty of Science, Geology Group, Brunei Darussalam
- Billon-Bruyat, Jean-Paul Section d'archéologie et paléontologie, Office de la culture, Porrentruy, Switzerland
- Spezzaferri, Silvia Département des Géosciences, Université de Fribourg, Switzerland
- Vennemann, T. Institut des Dynamiques de la Surface Terrestre, Université de Lausanne, Switzerland
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07.12.2015
Published in:
- Biogeosciences. - 2016, vol. 12, no. 23, p. 6945–6954
English
Chondrichthyan teeth (sharks, rays, and chimaeras) are mineralized in isotopic equilibrium with the surrounding water, and parameters such as water temperature and salinity can be inferred from the oxygen isotopic composition (δ18Op) of their bioapatite. We analysed a new chondrichthyan assemblage, as well as teeth from bony fish (Pycnodontiformes). All specimens are from Kimmeridgian coastal marine deposits of the Swiss Jura (vicinity of Porrentruy, Ajoie district, NW Switzerland). While the overall faunal composition and the isotopic composition of bony fish are generally consistent with marine conditions, unusually low δ18Op values were measured for the hybodont shark Asteracanthus. These values are also lower compared to previously published data from older European Jurassic localities. Additional analyses on material from Solothurn (Kimmeridgian, NW Switzerland) also have comparable, low-18O isotopic compositions for Asteracanthus. The data are hence interpreted to represent a so far unique, freshwater-influenced isotopic composition for this shark that is classically considered a marine genus. While reproduction in freshwater or brackish realms is established for other hybodonts, a similar behaviour for \textit{Asteracanthus} is proposed here. Regular excursions into lower salinity waters can be linked to the age of the deposits and correspond to an ecological adaptation, most likely driven by the Kimmeridgian transgression and by the competition of the hybodont shark Asteracanthus with the rapidly diversifying neoselachians (modern sharks).
- Faculty
- Faculté des sciences et de médecine
- Department
- Département de Géosciences
- Language
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- English
- Classification
- Palaeontology
- License
- License undefined
- Identifiers
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- RERO DOC 258862
- DOI 10.5194/bg-12-6945-2015
- Persistent URL
- https://folia.unifr.ch/unifr/documents/304793
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