Isotopologue thermometry of fossil hard tissues: A new approach to inferring dinosaur body temperature.

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Were dinosaurs cold-blooded or warm-blooded animals? There is growing evidence from physiological models, anatomical features, bone microstructure, and oxygen isotope data indicating that at least some dinosaurs were homeothermic or even endothermic. For a better understanding of the thermophysiology of dinosaurs and the gigantic sauropods in particular, dinosaur body temperatures will be determined using a novel chemical isotopologue thermometer based on the 13C-18Oexcess-temperature relation for carbonate minerals. This method will be calibrated for carbonate containing skeletal bioapatite by analyzing bones and enamel of extant vertebrates with known body temperatures. Preservation of the original isotope composition in fossil hard tissues is crucial for determining body temperatures of extinct vertebrates with this chemical thermometer. This will be tested by different mineralogical and geochemical methods. The 13C-18Oexcess of carbonate in well preserved dinosaur eggshells and tooth enamel apatite will be analyzed to determine the biomineralisation temperature of these biogenic hard tissues and hence the dinosaur body temperature. Teeth and eggshells of various sauropod taxa of different body size, ontogenetic age, and from a range of paleolatitudes, as well as teeth from sympatric ectothermic vertebrates will be analyzed to determine their body temperatures. Burial temperatures will be inferred from diagenetic carbonates of the embedding sediment or the altered dentine of the same tooth specimens.