Dinosaurs are a diverse group of reptiles that originated in the mid-Triassic and rapidly diversified into all of the large-bodied terrestrial vertebrate ecological niches in the Late Triassic and dominated this landscape for 150 million years. One of the largest controversies surrounding the dinosaurs were whether they were "warm-blooded" (high metabolic endotherms) or "cold-blooded" (low metabolic ectotherms). This study is to determine the thermal physiology in terrrestrial vertebrates, using oxygen isotopes to unlock the thermal physiology of Permian and Triassic terrestrial vertebrates.