A group of researchers at Caltech have figured out a way to take the temperature of dinosaurs, and finally lay to rest the old warm-blooded/cold-blooded debate — and the way they did it was more than a little brilliant.
Unfortunately, barring Michael Crichton levels of science fiction, we're not going to be able to stick a thermometer into a dinosaur any time soon, so researchers had to develop a new way to calculate how hot these creatures got, and they did so via their teeth. The isotopic analysis of teeth has been previously used to track population movements thanks to isotopes taken up into the teeth of organisms through their lifespan, but now these researchers have found a way to understand body temperature, too.
The new technique measures the concentration of clumps of carbon-13 and oxygen-18 within bioapatite, a mineral in the teeth. The amount these two isotopes bond together depends on the temperature of the host animal, with colder body temperatures leading towards more bonding.
Using this theory and the teeth of Brachiosaurii and Camarasaurii they found the former had a body temperature of around 38.2 °C/100.8 °F, and the latter 35.7 °C/96.3 °F. That's warmer than crocodiles and alligators, but cooler than birds — and just around mammals.
Unfortunately, it's not quite as easy as all that. While this may seem to suggest warm-bloodedness, the larger the animal, the hotter it tends to be, thanks to the heat retaining properties of being a mountain made out of meat. While the results seem to be on the warm side, for an animal that large they're actually colder than many models predicted. Which means we need more research, and more comparative samples in order to tell how accurate this method could be.