The body temperature of <i>Tyrannosaurus rex</i>.

Abstract

Despite an extensive history of study, quantitative constraints on the thermophysiology of <i>Tyrannosaurus rex</i> remain limited. Here, we derive a thermodynamically based determination of <i>T. rex</i> body temperatures from clumped isotopes in tooth enamel. Measurements of three <i>T. rex</i> teeth from the Late Cretaceous Hell Creek Formation yield a temperature of 36.3 ± 2.5°C (1 SE), comparable to modern endotherms. Teeth of coeval Hell Creek Formation crocodilians yielded temperatures significantly lower than did those of <i>T. rex.</i> Comparison with proxy-derived paleotemperatures and model simulations indicates that <i>T. rex</i> maintained a higher body temperature than its environment. Projected habitat suitability for <i>T. rex</i> based on these results shows that most of the North American paleocontinent, including colder and higher latitudes, were potentially accessible to the species.