Pushing the limits of bioapatite clumped isotope analysis: resolving endo- from ectothermy in mosasaurs

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We have recently demonstrated that the clumped isotopic composition of teeth of modern vertebrates is exclusively controlled by temperature. As such, the bioapatite clumped isotope thermometer may have the potential to resolve endo- from ectothermy in extinct vertebrates. However, an application of this new thermometer to small and medium sized extinct vertebrates is currently limited by the relatively large sample size (250-1250mg) of unaltered tooth enamel(oid) required for such analysis. Here, we request funding to significantly reduce this sample size by a factor of 15-20. We then aim at applying this new analytical setup to teeth from mosasaurs and contemporaneously deposited carbonate-bearing phases to clarify whether these marine reptiles were endo- or ectotherms. Their widespread abundance in the world’s ocean of the Upper Cretaceous allows to investigate if body temperatures varies with paleolatitude (40°N to 65°S) and body size or occurs decoupled from these parameters. Both mosasaur teeth and contemporaneously deposited carbonates and fish teeth will be intensively screened by an array of state-of-the-art analytical techniques to identify which parts of these samples were affected by diagenesis. Taken together, these systematic investigations are fundamental for an exploration of the potential of the bioapatite clumped isotope thermometer for the reconstruction of thermophysiology of small and medium sized extinct vertebrates.