Insights into Dinosaur Body Temperatures, Physiology, and Environments from Clumped Isotope Thermometry

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Insights into Dinosaur Body Temperatures, Physiology, and Environments from Clumped Isotope Thermometry PI: John M. Eiler Institution: California Institute of TechnologyThe first scientific description of dinosaurs was made nearly 170 years ago, but the ways in which they regulated their body temperatures remain a mystery. Dinosaurs could have been endotherms ("warm blooded") similar to birds and mammals, or might have been more similar to ectothermic ("cold blooded") reptiles such crocodiles and lizards, or perhaps depended on some intermediate metabolic strategy, such as "gigantothermy" the ability of some "cold blooded" animals to maintain high, stable body temperatures simply through great size. The PI will explore the body temperatures, and thereby the metabolisms, of dinosaurs using the most direct and quantitative measurements attempted to-date. He will use a novel geochemical approach, "clumped isotope" thermometry, which measures the temperature at which carbonate-bearing minerals, including carbonate-rich bio-apatite, formed based on the temperature-dependent ordering, or "clumping", of 13C and an 18O into bonds with each other. Initial results on modern and fossil mammals and well understood reptiles indicate this method can reconstruct the body temperature of an extinct species with an accuracy of 1-2oC. Our study will examine fossil remains of adult sauropod, theropod, and hadrosaur dinosaurs, co-existing crocodilians, as well as smaller juvenile and dwarf specimens of similar species. This project is expected to result in the first precise, quantitative measurements of dinosaur body temperatures; these data will have the potential to resolve one of the most long standing and well known debates in vertebrate paleontology. This project will be conducted with the help of undergraduate students from Caltech and a neighboring community college, and its results will be prepared for presentation to the broader public through the Los Angeles County Natural History Museum.