Researchers used microscopic isotope bonds preserved in tooth enamel to estimate Tyrannosaurus rex maintained about 97°F (36°C), providing the first direct temperature measurement for the species.
The method was improved to use roughly 90% less fossil material, allowing testing of museum specimens.
Results support an active, relatively fast-metabolism interpretation of T. rex rather than a slow, cold-blooded physiology.
# What the study found Researchers at UCLA applied a refined chemical technique to fossilized T. rex teeth and estimated the animal's core temperature at about 36°C (97°F). That temperature is nearly the same as humans and higher than modern cold-blooded reptiles, which typically sit around 28–30°C, but lower than many birds (40–43°C).
# Why this matters This is the first direct temperature measurement for T. rex. The number aligns with other evidence that some dinosaurs had metabolisms capable of generating and regulating internal heat rather than relying solely on external warming. A sustained body temperature near 36°C would help explain how T. rex stayed active and survived in cooler climates, including high-latitude fossil sites.
# How scientists took T. rex's temperature The measurement uses chemical bonds between rare isotopes of carbon and oxygen locked into tooth enamel. Those bonds form in temperature-dependent ratios: cooler conditions lead to more bonds, warmer conditions to fewer. Tooth enamel preserves these crystalline bonds far better than bone, which remodels over an animal's life.
# Who did the work and where it appeared The study's lead author was Randy Flores, with co-author and UCLA geobiologist Robert Eagle quoted explaining the result and method. The work was published Sept. 16, 2026, in Science Advances. The fossil material sampled belonged to Thomas the T. rex, held at the Natural History Museum of Los Angeles County.
# What the temperature implies about T. rex biology A core temperature near 36°C places T. rex closer to warm-blooded mammals than to modern reptiles. That temperature does not make it avian-hot (many birds are warmer), but it indicates a metabolism capable of consistent internal heat production. Such physiology supports sustained activity levels needed for active predation or scavenging and offers a straightforward explanation for T. rex fossils occurring in cooler regions.
# Method improvements and museum cooperation
# Takeaway Chemical signals locked in tooth enamel provided the first direct temperature estimate for T. rex. At about 36°C (97°F), the species appears to have sustained a warm internal temperature consistent with an active, high-energy lifestyle. The approach combines durable enamel chemistry with modern mass spectrometry and smaller sample needs, opening a path to similar measurements in other extinct animals.
Learn how more than a decade of lab work persuaded a museum to part with precious fossils, allowing researchers to take T. rex ’s temperature for the first time.
Using fossilized teeth, scientists have finally taken the T. rex’s temperature — and it wasn’t too different from our own. Researchers once thought that dinosaurs were sluggish, cold-blooded creatures. Later findings challenged that, suggesting that older dinosaurs were warm-blooded and could control their body tempera
Using fossilised teeth, scientists have finally taken the T. rex’s temperature – and it wasn’t too different from our own. Researchers once thought that dinosaurs were sluggish, cold-blooded creatures. Later findings challenged that, suggesting that older dinosaurs were warm-blooded and could control their body tempera
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