Big dinosaurs kept their cool

Body temperature of long-gone beasts resembled that of mammals

How do you take a dinosaur’s temperature? Very carefully.

ORAL THERMOMETER The number of chemical bonds between certain oxygen and carbon atoms in this fossil tooth allowed scientists to determine the body temperature of a 150-million-year-old sauropod dinosaur called Camarasaurus. Thomas Tütken/University of Bonn

By counting chemical bonds in 150-million-year-old fossilized teeth, scientists have done the paleontological equivalent of jamming a thermometer up a giant reptile’s rear end.