How Cold-Blooded Were the Dinosaurs?

Didn’t think you had much in common with a long-necked dinosaur? A thermometer might say otherwise.

The body temperature of enormous sauropods like Brachiosaurus and Apatosaurus that ruled the Jurassic period was similar to those of most birds -- and even akin to mammals like us, claims a new article published in Science magazine.

This peek into long-gone temperature comes from a most unusual place: teeth.

“We just did this with a collection of fossil teeth,” Dr. Robert Eagle, one of the two main research scientists for the project, told "We used a novel chemical technique which measured temperature by the way in which a mineral forms. The study we just published was the first time we had really taken this technique to test these fossil teeth from a dinosaur where we had no idea what its physiology was.”

The technique hinges on one of life’s most fundamental building blocks: the atom.

Many elements on the periodic table typically have what are called isotopes -- variants of elements in which the number of protons remains the same while the number of neutrons in the nucleus differ. The number of neutrons in an atom affects its overall molecular weight, which in turn affects its chemical properties.

Dr. Eagle, who conducted this research with Dr. John Eiler in Eiler's lab at Caltech University, simply studied differences among these isotypes that greatly depend on temperature.

“When we took the measurements, we got body temperatures around 36 to 38 degrees Celsius, which is similar to temperatures of most modern day mammals,” Dr. Eagle told “It’s certainly hotter than most modern cold blooded organisms, which range from 26 to 30 degrees Celsius. It gives us a new angle on this long standing problem on dinosaur physiology.”

Since the Jurassic period is considered to have been a blistering one, these temperature ranges suggest that sauropods had unique method to help cool themselves down. These could vary from genetic adaptations like an internal air sac or behavioral adaptations such as seeking shade during the middle of the day.

Though these findings can estimate temperature, they don’t provide a definite answer to the dispute of whether or not dinosaurs were hot or cold blooded. But it does provide something that doesn’t normally happen in regards to dinosaur physiology -- scientific consensus.

“It’s really a debate that’s been around for a long time,” Dr. Eagle told “When dinosaurs were first named as a group, people assumed they were slow lumbering reptiles. It wasn’t really until the 60s and 70s that people began to say they were more active creatures. Since then, I wouldn’t say there was a consistent opinion on dinosaur physiology. So our technique is unique in that sense.”

And with more chemical analysis, scientists could potentially solve even more fundamental mysteries, such as what exactly happened to Earth’s prehistoric inhabitants.

“One of the most exciting things that you could address with this technique is not just picking a dinosaur and saying its body temperature,” Dr. Eagle told You could also look at evolutionary adaptations between dinosaurs and birds, he noted, to "really try and figure out at what stage did warm bloodedness arise."

“That’s really the big picture, where this all arose in the geological record,” he said.