Dinosaurs: Were They Warm-Blooded or Cold Blooded Animals?

Some dinosaurs had the ability to warm themselves by drawing heat from the sun, according to a new study led by Robert Eagle and fellow scientists at the University of California, Los Angeles.

For over 150 years, scientists have debated the nature of dinosaurs' body temperatures and how those temperatures influenced their activity levels.

In their new research, UCLA scientists found that some dinosaurs were able to elevate their body temperature using heat sources in the environment, such as the sun. The researchers believe that dinosaurs were more active than modern-day alligators and crocodiles, which are active and energetic, but only in brief spurts, according to a news release.

Some dinosaurs had lower body temperatures than most modern birds, which are their living relatives, the study revealed.

The researchers examined six Argentine fossilized dinosaur eggshells, which were at Los Angeles County Natural History Museum and 13 eggshells from Mongolia's Gobi desert, which were well preserved. The main step was to determine if the fossilized eggshells maintained their initial chemistry or if they were altered from tens of millions of years ago. By assessing the shell's chemistry, the researchers were able to determine the temperature at which the eggs shells were formed, which was not known previously, according to the researchers.              

"This technique tells you about the internal body temperature of the female dinosaur when she was ovulating," said Aradhna Tripati, co-author of the study and a UCLA assistant professor of geology.

"This presents the first the direct measurements of theropod body temperatures," Tripati said.

The study concluded that Sauropods' body temperatures were warm - about 100 degrees Fahrenheit - while the smaller dinosaurs had lower temperatures, which were below 90 degrees.

The study found that some dinosaurs can categorized as both endotherms, warm blooded animals that produce heat internally and maintain their body temperature, and as ectotherms, cold-blooded animals that rely on external heat in the environmental.

"The temperatures we measured suggest that at least some dinosaurs were not fully endotherms like modern birds," Eagle said. "They may have been intermediate, somewhere between modern alligators and crocodiles and modern birds; certainly that's the implication for the oviraptorid theropods."

The researchers' experiment is the first study that was able to determine the exact body temperature of two types of dinosaurs, and it showed that they are different from each other, according to Tripati.

By assessing the fossilized soils and minerals from the oviraptorid theropods' nests, the researchers found that environmental temperature in Mongolia was about 79 degrees Fahrenheit, which was shortly before the dinosaurs went extinct.

"The oviraptorid dinosaur body temperatures were higher than the environmental temperatures, suggesting they were not truly cold-blooded, but intermediate," Tripati said.

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