We all know that dinosaurs are cold-blooded — or were they?

A new study has found that while dinosaurs were indeed lizards, which are cold-blooded by nature, they had a surprising ability to elevate their own body temperature, according to a Washington Post report.

Such animals are known as ectotherms, and while they get most of their heat from the environment — compared to endotherms like humans and mammals in general, which produce heat internally — they also had the ability to generate some heat within their bodies.

Dinosaurs, after all, are the ancestors to birds, which are endothermic creatures.

A new study published Tuesday in Nature Communications suggests that fossilized eggshells tell scientists that dinosaur metabolisms varied greatly among the different species.

Birds have much higher rates of metabolism than humans, making them very warm blooded, while sloth are at the coldest end of a “sliding scale” of warm bloodedness. That means merely describing an animal as warm-blooded or cold-blooded doesn’t go far enough — the question is where dinosaurs fall on that spectrum.

So a research team from the University of California analyzed some ancient eggshells to estimate the temperatures of a dinosaur’s body and figure out where they fall on the spectrum.

First, the scientists tested the method on modern eggs to see if their methods were accurate. Then they looked at the fossilized eggs, many of which showed too much decay to accurately determine body temperatures, but in two species, they were successful.

One, a long-necked titanosaur sauropod, showed a maternal body temperature of 100 degrees Fahrenheit, which is similar to large mammals, and a T-rex-like dinosaurs had a 90 degree body temperature.

Meanwhile, an analysis of the soil where they were found indicates the outside temperatures were actually lower, indicating that at least some of its heat was endothermic, settling the question.