Big Dinos Stayed Cool

Sauropod dinosaurs, the enormous plant-eating dinos with long tails and necks, had body temperatures ranging from 96.3 to 100.8 degrees Fahrenheit -- making them as warm as most mammals -- including people.

Because body temperature usually rises the larger an animal gets, the findings, published in the latest issue of Science, suggest huge sauropods had mechanisms for cooling themselves off.

"What we can say is that sauropods did not have body temperatures that were as cold as modern crocodiles and alligators," lead author Robert Eagle, a researcher at the California Institute of Technology, told Discovery News.

Eagle pointed out that many models had predicted that sauropods would have high body temperatures of over 104 degrees.

"This suggests that sauropods may have had cooling mechanisms to prevent very high body temperatures being reached due to their gigantic size," he said.

So-called "gigantotherms" maintain warm temperatures due to sheer size. Plant-eating dinosaurs may have then been cold-blooded, in the sense that they could have depended on their environment for heat, as opposed to generating it internally, as warm-blooded species do.

"If you're an animal that you can approximate as a sphere of meat the size of a room, you can't be cold unless you're dead," explained co-author John Eiler, a Caltech geochemist.

Eiler, Eagle and their colleagues made the determinations after studying 11 teeth belonging to Brachiosaurus brancai and Camarasaurus dinosaurs.

The scientists measured concentrations of the rare isotopes carbon-13 and oxygen-18 in bioapatite, a mineral found in teeth and bone. How often these isotopes bond with each other depends on temperature, so the lower the temperature, the more carbon-13 and oxygen-18 clumps exist. Measuring these clumps revealed the temperature of the environment in which the mineral formed inside the dinosaur.

This geochemical "thermometer" shows Brachiosaurus had a temperature of about 100.8 degrees, while Camarasaurus had a temperature of approximately 96.3 degrees.

Eagle said that Jurassic temperatures were probably "significantly hotter than today," so even if sauropods were cold-blooded they likely were not very restricted, in terms of habitat range, due to climate. In fact, they probably spent a lot of time trying to cool down their hefty bodies.

The researchers suspect the long necks and tails of these animals might have dispelled some heat. Lower metabolic rates might have helped to reduce internal warmth.

Read more at Discovery News