T-Rex may be the most famous extinct animal on Earth, but scientists are still uncovering remarkable details about how this enormous predator actually lived. A new study has now given paleontologists something they have never had before: a direct estimate of T-Rex’s body temperature. And the answer is surprisingly familiar.
Taking the Temperature of a T-Rex
Researchers studied three fossilized T-Rex teeth from the Late Cretaceous Hell Creek Formation in Montana. Rather than looking only at the shape or structure of the teeth, they examined chemical signatures preserved within the tooth enamel.
Using a technique called clumped isotope thermometry, scientists can analyze bonds between rare isotopes of carbon and oxygen. Because these bonds form differently depending on temperature, the chemistry preserved in tooth enamel can provide an estimate of the animal’s body temperature when the enamel formed.
The result?
The three T-Rex teeth produced an average estimated body temperature of 36.3°C, or about 97°F.
Surprisingly Close to Modern Mammals
That temperature is remarkably similar to those of large living mammals. The researchers noted that African and Indian elephants maintain body temperatures around 36°C.
Modern birds, the closest living relatives of dinosaurs, generally run hotter. Many birds maintain body temperatures around 40°C or higher.
So while T-Rex may not have run quite as hot as many modern birds, its estimated temperature looks much more like that of a warm-blooded animal than a typical cold-blooded reptile.
What About Crocodilians?
The researchers had another useful comparison.
They also analyzed fossil crocodilian teeth from the Hell Creek Formation. Those teeth produced an average estimated temperature of about 30.9°C, significantly cooler than the T-Rex teeth and consistent with the kind of ectothermic, or cold-blooded, physiology seen in crocodilians today.
The comparison is especially important because the animals lived in the same general ecosystem. The researchers concluded that T-Rex maintained a body temperature higher than its surrounding environment, adding to existing evidence for endothermy in theropod dinosaurs.
Why T-Rex Matters to Paleontology
Scientists know an extraordinary amount about T-Rex, from its anatomy and growth to aspects of its biology and ecology. That makes it an important reference point when researchers investigate other dinosaurs.
But this discovery also raises new questions.
Did other large theropod dinosaurs maintain similarly high body temperatures? What about plant-eating dinosaurs? Did different dinosaur groups regulate their temperatures in different ways?
One study cannot answer all of those questions. In fact, the researchers themselves note that body temperature alone does not reveal every detail of an extinct animal’s metabolism. But fossil chemistry is giving paleontologists another powerful way to investigate questions that bones alone cannot answer.
And perhaps one day, a future paleontologist will help uncover the next piece of the puzzle.
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