The researchers asked whether carbonate bonds preserved in T. rex tooth enamel could provide a quantitative body-temperature estimate, and whether that estimate was higher than environmental and crocodilian temperatures in a way consistent with internal heat production.
The research question and why it matters
The researchers asked whether carbonate bonds preserved in T. rex tooth enamel could provide a quantitative body-temperature estimate, and whether that estimate was higher than environmental and crocodilian temperatures in a way consistent with internal heat production.
Bone oxygen-isotope studies in the 1990s argued that T. rex maintained fairly even temperatures across its body, while later work on dinosaur growth, anatomy and biogeography increasingly supported elevated metabolism in theropods. Earlier isotope results were debated because fossil chemistry can change after burial and because giant animals can retain heat. This study applies a refined clumped-isotope method to resistant tooth enamel, uses far less fossil material than earlier versions and adds a same-site crocodilian check.
What researchers found
The three T. rex teeth produced a mean temperature of 36.3 ± 2.5°C, while the five crocodilian teeth averaged 30.9°C. The T. rex value was higher than the reconstructed surroundings and broadly comparable with large living mammals. Coupling that estimate to paleoclimate simulations made most of Late Cretaceous North America—including colder, higher-latitude regions—thermally plausible habitat.
Key results from the tested systems
T. rex teeth
The estimate came from two individuals at one Hell Creek locality.
estimated temperature
Mean clumped-isotope result reported with one standard error.
crocodilian comparison
Five teeth from the same formation yielded a lower mean.
enamel per sample
Method refinements reduced the amount of irreplaceable fossil needed.
How the research worked
The team drilled roughly 5 milligrams of enamel powder from each fossil, dissolved it in phosphoric acid and measured how often rare carbon and oxygen isotopes were bonded together in the released carbon dioxide. Because those bonds form more often at lower temperatures, their abundance acts as a clumped-isotope thermometer. The T. rex estimates were compared with five crocodilian teeth from the same formation, proxy-derived environmental temperatures and climate-model simulations used to map potentially suitable habitat.
How to interpret this design
The result is conditional on the model structure, inputs, boundary conditions and scenarios chosen by the researchers. Agreement with known observations strengthens confidence, but a projection is not a direct observation of the future or the inaccessible past.
The conclusion is drawn from preserved material and its context. Dating, contamination control, site history, sample preservation and representativeness determine how far the interpretation can extend.
What strengthens or limits the finding?
The study used a physically grounded thermometer, reported uncertainty and checked preservation with crocodilian teeth from the same formation. Its headline estimate rests on three T. rex teeth from two animals, and temperature alone cannot fully distinguish active endothermy from heat retained because of enormous body size.
This is an early signal that deserves attention and replication, not a result that should yet carry the weight of mature, independently confirmed research.
Funding and disclosure context
The recorded funding source is: National Science Foundation grants EAR-1352212 and ICER-1936715; Royal Society grants RSWVF/R2/212004 and NIF/R1/231802; Heising-Simons Foundation grants 2021-3137, 2022-3314 and 2024-5453; and BBC Natural History Unit/Apple TV+ award A100198-102. The complete conflict-of-interest declaration should be checked in the original publication rather than inferred. Funding or a disclosed relationship does not by itself invalidate a result, but it is relevant when judging design choices, analysis and the need for independent replication.
What it means
A quantitative estimate narrows the range of plausible T. rex physiology. Maintaining a temperature around 36°C would support sustained activity and a wider geographic range, while also implying a substantial food requirement. The most defensible conclusion is that these specimens were warmer than their environment; the precise metabolic mechanism still needs evidence from more individuals, tissues and species.
Deeper analysis
The comparison matters as much as the headline number
If burial chemistry had reset all teeth toward the same temperature, the T. rex and crocodilian values should have converged. Their separation does not eliminate every preservation concern, but it makes a simple shared alteration explanation less likely.
Warm is not automatically warm-blooded
A large body loses heat slowly, and behavior can also change body temperature. The higher-than-environment estimate supports thermoregulation and is consistent with endothermy, yet temperature alone does not quantify metabolic rate or exclude every alternative heat source.
Sample size limits biological generalization
Three teeth can demonstrate that the method works on prized fossils and produce a specimen-level estimate. Population claims require teeth from more animals, growth stages, localities and climates.
The ecological implications are conditional
A warmer animal could remain active in cooler conditions and would need more energy than a comparable ectotherm. Translating that physiology into hunting style, speed or daily food intake requires biomechanics and ecology beyond the isotope measurement.
What it does NOT prove
- It does not prove that every T. rex maintained exactly 36.3°C throughout life, seasons or the day.
- It does not by itself distinguish metabolic heat production from all contributions of large-body heat retention, behavior or local climate.
- It does not show that T. rex could run at any particular speed or that it hunted rather than scavenged.
- It does not establish that all dinosaurs were warm-blooded or shared one metabolic strategy.
- It does not directly measure a living animal; it infers formation temperature from fossil enamel chemistry.
Important limitations
- Only three T. rex teeth from two individuals at one Montana locality were analyzed.
- The ±2.5°C uncertainty is the reported standard error around the mean and does not capture every source of fossil alteration or ecological variation.
- Clumped-isotope estimates depend on calibration, sample preservation and assumptions about when and how enamel formed.
- The crocodilian comparison helps test alteration but contains only five teeth and is not a complete environmental thermometer.
- Habitat suitability came from climate simulations constrained by the temperature estimate, not direct evidence that T. rex occupied every modeled region.
- Complete conflict-of-interest information was not available in the accessible sources reviewed for this page.
How this fits with previous research
Bone oxygen-isotope studies in the 1990s argued that T. rex maintained fairly even temperatures across its body, while later work on dinosaur growth, anatomy and biogeography increasingly supported elevated metabolism in theropods. Earlier isotope results were debated because fossil chemistry can change after burial and because giant animals can retain heat. This study applies a refined clumped-isotope method to resistant tooth enamel, uses far less fossil material than earlier versions and adds a same-site crocodilian check.
Questions still unanswered
- Will teeth from other individuals, ages, regions and seasons reproduce the 36.3°C estimate?
- How much of the temperature came from metabolic heat versus gigantothermy and behavior?
- Did juveniles and adults regulate heat in the same way?
- How did other tyrannosaurs and non-theropod dinosaurs compare?
- Can independent laboratories replicate the result with different clumped-isotope calibrations?
Relevant U.S. government resources
These resources serve different purposes. A registry can verify what researchers planned, a repository can locate government-funded work, and an agency page can supply authoritative background. None automatically proves that this paper's conclusion is correct.
USGS Publications Warehouse ↗
The authoritative catalog of USGS scientific publications, used to check related government research and long-term observational context.
NOAA research and data ↗
Federal observations and research on climate, oceans, atmosphere and ecosystems provide context for environmental claims. They do not automatically validate a separate model or paper.
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Three T. rex teeth yielded a body-temperature estimate near 36.3°C
This review was developed from the source record below and, when separately available, the primary paper or government report. The summary and analysis on this page are original editorial writing.
- Source organization
- University of California, Los Angeles
- Source type
- University
- Authors
- Randon J. Flores, Robert A. Eagle, Robin B. Trayler, Gabriele Larocca Conte, Sora L. Kim, Alfio Alessandro Chiarenza, Alex Farnsworth, Paul J. Valdes, Luis Chiappe and Aradhna Tripati
- Journal / report
- Science Advances
- Publication date
- September 16, 2026
- DOI
- 10.1126/sciadv.aeb7653
- PMID
- Not available
- Institution
- University of California, Los Angeles; University of California, Merced; University College London; University of Bristol; Chinese Academy of Sciences; Chapman University; North Carolina Museum of Natural Sciences; and Natural History Museum of Los Angeles County
- Funding
- National Science Foundation grants EAR-1352212 and ICER-1936715; Royal Society grants RSWVF/R2/212004 and NIF/R1/231802; Heising-Simons Foundation grants 2021-3137, 2022-3314 and 2024-5453; and BBC Natural History Unit/Apple TV+ award A100198-102
- Conflicts
- Not available in the accessible institutional report and article metadata reviewed for this page
- Open access
- Yes
- Reuse approach
- Methods and results summarized independently from UCLA's institutional report, the open peer-reviewed article record and an independent report; no source wording, fossil photographs, illustrations, figures or tables reproduced.
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