Intra-skeletal variability in phosphate oxygen isotope composition of marine vertebrates as a tool to track regional heterothermies in mesozoic marine reptiles
Résumé
Marine vertebrates use various strategies to regulate their body temperature, which can result in local temperature variations. Many extant marine endothermic organisms let the temperature of some areas of the body drop to limit heat loss, whereas some ectotherms are able to generate heat locally to improve visual acuity in cold environment, swim faster or migrate over longer distances. These strategies lead to temperature heterogeneities called regional heterothermies that can be measured on extant organisms using thermometry.
Such heterogeneities are however poorly constrained in extinct marine vertebrates.
In this study, we have analyzed the oxygen isotope composition of phosphatic skeletal elements (δ18Op) of five extant regional heterotherms (dolphins, swordfish and Atlantic bluefin tuna) to assess whether regional heterothermies can be monitored using their δ18Op values. The results indicate a consistent link between δ18Op variations and temperature heterogeneities recorded by classical methods and demonstrate the robustness of this method to track regional heterothermies using skeletal remains. We will also present preliminary intra-skeletal δ18Op data obtained on Mesozoic ichthyosaurs and plesiosaurs and discuss their implications for the thermophysiology and ecology of these large extinct marine predators that dominated the oceans during the Mesozoic.