A thermometer back in time.

To test their method, scientists have determined from the tooth body temperature of living species such as elephant or shark. Successfully. (Florida Museum of Natural History)Keywords: paleontology, Dinosaurs, temperature.

By analyzing the atomic composition of teeth and bone fossils, scientists can now measure the body temperature of extinct species. A technique that will ultimately whether or not dinosaurs were warm-blooded.

Dinosaurs were they able to regulate their body temperature like mammals, or they depended on external conditions such as lizards? When the first warm-blooded animals they get there? Why? All these questions and many others, will probably soon replies with an international team led by researchers at the California Institute of Technology (Caltech). They have indeed developed a new method to determine body temperature of vertebrates from their fossilized bones. The calibration results of this method are published online Monday in The Proceedings of the National Academy of Sciences (PNAS). And they are very encouraging.
"It's not quite like going back in time and insert a thermometer into the foundation of a creature, but it comes close," says one of the co-authors of the study, professor of geochemistry at Caltech . To determine the temperature of an extinct, it had so far rely on its diet, its anatomy and behavior alleged, and assumptions. The method proposed by Robert Eagle, lead author of the study, is radically different.
Two isotopes* Carbon and oxygen, respectively, carbon-13 and oxygen-18, have a tendency to associate with each other during the formation of some crystals called bioapatite component of tooth enamel, shell eggs and bones. Depending on the temperature of formation of these crystals, the number of atomic pairs specific ranges. It is therefore possible to determine the temperature of formation of a tooth or a bone by measuring the quantity of these atoms append. And therefore go back to the body temperature of animals to which they belonged at the precise moment the piece of tooth or bone study was designed.

Slice the debate about dinosaurs:
To confirm their theory, Robert Eagle proceeded with his team in action on the bones of species still living, such as elephants, crocodiles or sharks. With one or two degrees, geochemists have found the exact body temperature of these species. By focusing on extinct species, aged only a few thousand years, as the mammoth or certain types of rhinos, they have found temperatures in perfect harmony with existing estimates based on very good knowledge of these animals close enough their direct descendants.
Now that researchers have a "thermometer" calibrated, they will go without delay in time. First stop on the trip back, the dinosaurs. "We are already some teeth to see if the main species were warm-blooded or cold blooded," enthuses Robert Eagle. It must be said that this hot debate has never been settled definitively and is regularly the subject of virulent clashes.
But this method should also learn indirectly paleoclimatologists. The temperature of the cold-blooded animals in direct relation to external conditions, scientists will have in effect with this new tool "paleothermometers.

* Isotope: an atom is defined by the number of protons in its nucleus (a carbon atom has 6). Depending on the number of neutrons in the nucleus also contained, the same element has different isotopes. Carbon-14, for example, who used to date fossils or objects, is an isotope of carbon containing 8 neutrons (added to 6 protons, it is 14 nucleons, hence the name carbon-14). The carbon-12 contains only six neutrons (nucleons or 12).