T. rex teeth indicate it ran as warm as an elephant

UCLA geochemists measured the body temperature of T. rex using clumped isotope thermometry on enamel from three teeth from the Hell Creek Formation. The average result was 36.3 ± 2.5 °C, close to modern elephants and higher than coexisting crocodiles (30.9 °C).

• Temperature of two teeth from a young T. rex: 37.3 °C and 35.9 °C
• Third tooth gave 34.7 °C, sample average 36.3 ± 2.5 °C
• Crocodiles in same ecosystem: average 30.9 °C
• Summer water in Hell Creek about 26 °C, climate model max 33 °C