Scientists find dinosaurs had warm blood

The Wenatchee World: Scientists find dinosaurs had warm blood

LOS ANGELES — Millions of years after dinosaurs roamed the Earth, scientists have taken their temperature and reported that their bodies operated between 96.8 and 100.4 degrees Fahrenheit.

That temperature could mean that dinosaurs were warm-blooded like birds, their modern-day feathered descendants, the researchers reported Thursday in the journal Science. But it’s also possible that they were cold-blooded like the reptiles they resemble and that they developed large bodies that allow them to stay warm without requiring a huge investment in energy and metabolism, they said.

Either way, “if you walked up to a dinosaur, it would feel like a cow,” said John Eiler, a geologist and geochemist at Caltech and the study’s senior author.

To figure out their body temperature, Eiler and his colleagues relied on the fact that atoms tend to clump with other atoms of similar weight, and that the strength of those bonds depends on temperature. If the temperature is low, the atoms will bond tightly; if the temperature is high, the bonds will be weaker.

The research team examined fossilized teeth from large sauropods from multiple sites during the Jurassic period, which ended about 145 million years ago. They focused on the enamel because it was much better preserved than other parts of the teeth.

By zeroing in on the ratio of heavy carbon bonded to heavy oxygen, the scientists were able to calculate that the creatures were quite warm, as warm as modern-day birds and mammals.

“The technique is rather elegant,” said John Harris, chief curator of the George C. Page Museum in Los Angeles, who was not involved in the study.

The question of whether dinosaurs regulated their own body temperatures or were dependent on heat from the environment has been a matter of scientific debate for decades.

Until the 1960s, they were presumed to be cold-blooded. But more recently, evidence about their anatomy, habitat, growth rate and behavior has emerged, suggesting that they might be warm-blooded.

While the study doesn’t settle this controversy, it does provide scientists with a new avenue to pursue questions related to animal evolution and the development of warm-blooded creatures.

Eiler said he plans to study the teeth of sauropod dwarfs and other small dinosaurs to see if their body temperatures were lower than the dinos in this study.

If so, he said, that would suggest that the bigger dinosaurs used their size — rather than an internal thermostat — to stay warm.