T. rex’s 66‑million‑year‑old tooth reveals body temperature nearly human

Chemical signatures inside a fossilized Tyrannosaurus rex tooth, dated 66 million years ago, indicate the dinosaur maintained a body temperature of about 97 °F—almost identical to that of modern humans. The analysis, based on preserved isotopic and molecular markers, provides the first direct evidence that T. rex was warm‑blooded. This metabolic trait explains how the massive predator could remain active and survive in the cold climates of northern North America, including Alaska, during the late Cretaceous. The discovery refines our understanding of dinosaur physiology and supports the hypothesis that large theropods possessed endothermic metabolisms similar to those of contemporary mammals and birds.