First we thought that dinosaurs were cold-blooded, just like modern-day lizards. Then we thought that they might be warm-blooded. Then we realized that, short of cloning one, it was impossible to prove it one way or another. Or is it?

A team of researchers at Caltech have come up with a cunning technique that involves measuring concentrations of carbon and oxygen isotope in sauropod teeth. In an article in the latest issue of Science they report measurements for Brachiosaurus and Camarasaurus, revealing that the giant beasts had blood temperatures in the range 36° – 38°C.

Unfortunately (or fortunately depending on how you look at it), this hasn’t solved the mystery. You see, the bigger and animal is, the hotter it gets. Elephants have warmer blood than we do (which I guess may explain why they are no longer hairy). Calculations for sauropods suggest that their blood should be up around 40° – 45°C, which would cook their innards. So clearly they had some means of keeping cool. Or maybe they kept their blood warm in a different way than we do. It is all, still, very mysterious.