Study confirms T. rex was warm-blooded with a human-like temperature

Overview

Updated 1 hour ago

A Tyrannosaurus rex ran a body temperature of about 97 degrees Fahrenheit in life, nearly identical to a modern human. Chemists extracted the figure from rare isotope bonds preserved in fossilized tooth enamel — the first direct temperature measurement of the dinosaur.

The study, published September 16 in Science Advances, settles a dispute that has split paleontologists since the 1970s over whether T. rex was a warm-blooded hunter or a cold-blooded reptile. A warm-blooded T. rex needed far more food and could have roamed as far as the Arctic, which changes how scientists picture the entire Cretaceous food web.

Why it matters

A warm-blooded T. rex needed far more food and could roam Arctic territory, reshaping how scientists understand the Cretaceous ecosystem.

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Key Indicators

97.3°F (36.3°C)

T. rex body temperature

Measured from clumped isotopes in three fossil teeth from Montana.

±4.5°F (±2.5°C)

Measurement uncertainty

The margin of error around the 97.3°F estimate.

86°F (30°C)

Ancient crocodilian temperature

A same-site fossil reptile read 30°C, confirming the method distinguishes warm from cold-blooded animals.

Teeth analyzed

Three Tyrannosaurus rex teeth from the Hell Creek site in Montana.

Voices

Curated perspectives — historical figures and your fellow readers.

Ever wondered what historical figures would say about today's headlines?

People Involved

Randy Flores

Lead study author, UCLA researcher

Published the temperature measurement in Science Advances

Robert Eagle

UCLA geobiologist, study co-author

Co-authored the Science Advances paper

Alessandro Chiarenza

Paleontologist, University College London, study co-author

Modeled T. rex's potential range from the measured temperature

Aradhna Tripati

UCLA isotope geochemist, senior study author

Led the lab that performed the isotope analysis

Organizations Involved

University of California, Los Angeles

Public research university

Led the study and developed the clumped isotope technique for fossils

Led the study and developed the clumped isotope technique for fossils.

Science Advances

Peer-reviewed scientific journal

Published the study on September 16, 2026

Peer-reviewed journal that released the T. rex temperature study.

Natural History Museum of Los Angeles County

Museum

Houses Thomas the T. rex, whose teeth were analyzed

Provided the T. rex teeth used in the temperature analysis.

Timeline

1 event Latest: Yesterday

September 2026
UCLA team measures T. rex body temperature
Latest Research

Clumped isotope analysis of tooth enamel puts T. rex at about 97°F, confirming warm-blooded metabolism.
Yesterday

Scenarios

Clumped isotope method expands across the dinosaur family tree

Likely Resolves by End of 2027

Discussed by: UCLA team and study co-authors, who note the technique can apply to other fossils

The method just proved workable on 66-million-year-old enamel. Other teams will likely apply it to sauropods, hadrosaurs, and smaller theropods to map how dinosaur metabolism evolved. Each new measurement either extends or complicates the warm-blooded picture; conflicting readings on other species would keep the debate alive.

Paleontologists contest the endothermy conclusion

Possible Resolves by Q2 2027

Discussed by: Researchers who have argued dinosaurs were mesotherms (in between warm and cold-blooded)

Some paleontologists may argue a single body temperature does not prove endothermy. A 97°F reading could reflect inertial homeothermy — a large body simply retaining heat — rather than active metabolism. A peer-reviewed rebuttal would question whether the measurement distinguishes the two.

Arctic T. rex range confirmed by new fossil finds

Possible Resolves by End of 2030

Discussed by: Alessandro Chiarenza, University College London

Chiarenza's paleoclimate modeling says a 97°F T. rex could survive from Mexico to Alaska. Tyrannosaur fossils already come from Alaska; new field work in high-latitude deposits could test the prediction directly. Confirming finds would validate the warm-blooded model's ecological consequences.

Historical Context

3 moments from history that rhyme with this story — and how they unfolded.

1969-1975

Dinosaur Renaissance (1969)

Paleontologist John Ostrom described Deinonychus, a swift, agile predator, and argued dinosaurs were warm-blooded and active, overturning the image of sluggish reptiles. Robert Bakker popularized the idea through the 1970s against fierce resistance.

Then

Ignited a decades-long dispute between hot-blooded and cold-blooded camps in paleontology.

Now

Led to the modern view of dinosaurs as dynamic animals, setting the stage for this measurement.

Why this matters now

This study provides the first direct temperature evidence backing the warm-blooded hypothesis Ostrom proposed nearly six decades ago.

1996-2000s

Feathered dinosaurs from Liaoning, China (1996-2000s)

Quarry workers in Liaoning Province uncovered Sinosauropteryx, a small dinosaur preserved with feather-like filaments. Further finds cemented the link between birds and dinosaurs and showed many dinosaurs had insulating coverings consistent with active metabolisms.

Then

Rewrote how dinosaurs were reconstructed and established birds as living dinosaurs.

Now

Feathers in non-avian dinosaurs strengthened the case that warm-blooded metabolism predated birds.

Why this matters now

Feathers suggested but could not prove endothermy; this study supplies the temperature evidence that feathers implied.

2014

Mesothermy proposal (2014)

John Grady and colleagues published in Science proposing dinosaurs were mesotherms, able to generate some body heat without sustaining mammal or bird temperatures. The model aimed to explain dinosaur growth rates and ecological dominance.

Then

Added a third option to the binary warm/cold-blooded debate and became the leading alternative view.

Now

Set up a testable prediction: dinosaur body temperatures should sit between reptiles and mammals.

Why this matters now

The 97°F reading directly tests the mesothermy model and finds T. rex ran warmer than mesothermy would predict.