A thermometer to measure dinosaur body temperature: scientists show direct evidence of warm-bloodedness in giant sauropods

It was speculated for a few decades now that dinosaurs were endotherm (warm-blooded) creatures with high metabolism rates, comparable to birds and mammals. But all the gathered evidences were so far indirect and quite speculative. These include the fact that dinosaurs also thrived in polar climates, or that the spacing in dinosaur tracks show that they were able to run pretty fast.

Now a team of scientists from Caltech led by John Eiler found a way to directly measure the body temperature of long extinct animals. The team measured the concentrations of the rare isotopes carbon 13 and oxygen 18 in the mineral bioapatite found in dinosaur teeth. These isotopes would bond (“clump”) together more often with lower temperature, so measuring the clumping of the two isotopes can precisely tell the temperature the teeth were at when the animal was alive.

The method was applied to well preserved teeth of big upper Jurassic sauropods (Brachiosaurus and Camarasaurus) and the results show that their body temperature ranged between 36 to 38 ºC, which are comparable to mammals but a bit lower than what would have been predicted if endothermy were solely due to the gigantic size of these dinosaurs. This is an indication that sauropods must have developed efficient physiological or behavioral ways to regulate their body temperature to prevent overheating.

The idea is now to use the isotopic thermometer to measure the body temperature of a larger set of extinct animals, including the smaller dinosaurs that can't rely on size for endothermy.

References:

Robert A. Eagle, Thomas Tütken, Taylor S. Martin, Aradhna K. Tripati, Henry C. Fricke, Melissa Connely, Richard L. Cifelli, and John M. Eiler, 2011, “Dinosaur Body Temperatures Determined from Isotopic (13C-18O) Ordering in Fossil Biominerals” Science, advanced online publication.