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T. rex teeth indicate it ran as warm as an elephant - Ars Technica (opens in a new tab)

T. rex teeth indicate it ran as warm as an elephant · 2026-09-20

Short answerEvidenceSource

Short answer

Mostly supported

Mostly supported.

The claims we could check match the study, but some claims were not covered by the evidence reviewed.

  • 3 supported
  • 1 not covered

Checked against the study summary. The full text wasn't available, so some details couldn't be settled either way.

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NewsLink checks it

Mostly supported

Every claim we could check holds up. Three of four claims match the study. This overall rating is based only on the claims we could check. One claim the study doesn't address.

  • 3 supported
  • 1 not covered
Open claim evidence
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Evidence layer

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Each claim gets a verdict. Expand it to see the evidence directly below.

4 claims in this story

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Claim 1 of 4Not coveredThe article says clumped isotope thermometry in tooth enamel can record body temperature because the bonding of heavy isotopes depends on the temperature at which the enamel formed.View evidenceHide evidence

Why this verdict

The paper profile supports that clumped-isotope thermometry of tooth enamel was used, but the abstract-level evidence supplied here does not spell out the mechanistic explanation that heavy-isotope bonding/clumping depends on enamel-formation temperature. That explanation is scientifically plausible for the method, but it is not directly verifiable from the supplied abstract-level profile.

1

Study evidence

Clumped-isotope analysis of three Tyrannosaurus rex teeth yields an estimated body temperature of 36.3 ± 2.5°C (1 SE).36.3 ± 2.5°C (1 SE)

“we derive a thermodynamically based determination of T. rex body temperatures from clumped isotopes in tooth enamel”
Claim 2 of 4SupportedResearchers had long debated T. rex physiology and whether it used warm blood to power its activity.View evidenceHide evidence

Why this verdict

The paper profile frames the study as providing quantitative constraints on T. rex thermophysiology and reports an endotherm-like body-temperature estimate, with further comparison to environmental temperatures. The story’s hedged framing that T. rex physiology/warm-bloodedness was a debated question is consistent with that abstract-level framing.

1

Study evidence

Clumped-isotope analysis of three Tyrannosaurus rex teeth yields an estimated body temperature of 36.3 ± 2.5°C (1 SE).36.3 ± 2.5°C (1 SE)

“we derive a thermodynamically based determination of T. rex body temperatures from clumped isotopes in tooth enamel”
2

Study evidence

Integration of enamel clumped-isotope temperatures with proxy paleotemperatures and model simulations indicates Tyrannosaurus rex maintained a body temperature higher than ambient environmental temperatures.

“Comparison with proxy-derived paleotemperatures and model simulations indicates that T. rex maintained a higher body temperature than its environment.”
Claim 3 of 4SupportedA team led by Randon J. Flores and Robert A. Eagle at UCLA measured T. rex body temperature by analyzing its teeth.View evidenceHide evidence

Why this verdict

The core claim that the study estimated/measured T. rex body temperature by analyzing tooth enamel is supported: the abstract profile reports clumped-isotope thermometry on three T. rex teeth yielding a temperature estimate. The supplied paper profile does not independently verify the leadership names or UCLA affiliation, but the scientific method/result portion of the claim is supported at abstract depth.

1

Study evidence

Clumped-isotope analysis of three Tyrannosaurus rex teeth yields an estimated body temperature of 36.3 ± 2.5°C (1 SE).36.3 ± 2.5°C (1 SE)

“we derive a thermodynamically based determination of T. rex body temperatures from clumped isotopes in tooth enamel”
Claim 4 of 4SupportedThe dental thermometer read about 36° Celsius, roughly the body temperature of a modern elephant.View evidenceHide evidence

As statedabout 36° Celsius

Why this verdict

The reported value is supported by the abstract profile: measurements of three T. rex teeth yielded 36.3 ± 2.5°C, matching the story’s 'about 36°C.' The specific comparison to a modern elephant is not stated in the supplied profile, though the profile does say the estimate is comparable to modern endotherms.

1

Study evidence

Clumped-isotope analysis of three Tyrannosaurus rex teeth yields an estimated body temperature of 36.3 ± 2.5°C (1 SE).36.3 ± 2.5°C (1 SE)

“we derive a thermodynamically based determination of T. rex body temperatures from clumped isotopes in tooth enamel”
Then look for missing context

Context layer

What the story left out

Important study details the story did not include.

  • Sampling basis: the T. rex estimate came from three teeth from the Late Cretaceous Hell Creek Formation.

    The story mentions teeth generally but does not report the small sample size or the Hell Creek Formation sampling context, both of which matter for interpreting generalizability.

    From Clumped-isotope thermometry on tooth enamel (ex vivo fossil samples)

  • Comparative result: coeval Hell Creek crocodilian teeth yielded temperatures significantly lower than T. rex teeth.

    This comparator result is a material support for interpreting T. rex thermophysiology within the same paleoenvironment, but it is not included in the supplied story presentation.

    From clumped-isotope thermometry on crocodilian enamel (comparative)

  • Model/proxy integration: the paper compared enamel-derived temperatures with proxy-derived paleotemperatures and model simulations.

    The story’s summary focuses on tooth enamel thermometry and the warm-bloodedness debate, but does not describe the abstract’s integration with paleotemperature proxies and simulations.

    From in_silico integration with proxy paleotemperatures

  • Downstream biogeographic projection: habitat-suitability modeling suggested most of the North American paleocontinent, including colder/higher latitudes, was potentially accessible to T. rex.

    This is a distinct abstract-level paper contribution, but it is not reflected in the supplied story claims or caveats.

    From habitat suitability modeling / spatial projection (in silico)

2 things the story did carry across
  • Core result: clumped-isotope thermometry on T. rex tooth enamel yielded an estimated body temperature of 36.3 ± 2.5°C.
  • Interpretation: the enamel-derived temperature is consistent with endotherm-like body temperature and with T. rex maintaining a body temperature higher than ambient environmental temperatures.
Then read the study layer

Study layer

Study at a glance

Scan the study first. Expand only the parts you want to inspect.

Pieces of work

4

Evidence read

study summary

Lead result

ex vivo animal

1Lead resultex vivo animalEstimate Tyrannosaurus rex body temperature using clumped-isotope thermometry of tooth enamel, providing quantitative constraints on its thermophysiology (endotherm-like body temperature).Clumped-isotope thermometry on tooth enamel (ex vivo fossil samples)Expand

In plain English

Clumped-isotope thermometry on enamel from three Tyrannosaurus rex teeth from the Late Cretaceous Hell Creek Formation produced an absolute body-temperature estimate of 36.3 ± 2.5°C (1 SE), consistent with endotherm-like body temperatures and higher than co-occurring crocodilian enamel temperatures.

Key findings

  • Clumped-isotope analysis of three Tyrannosaurus rex teeth yields an estimated body temperature of 36.3 ± 2.5°C (1 SE).36.3 ± 2.5°C (1 SE)
“we derive a thermodynamically based determination of T. rex body temperatures from clumped isotopes in tooth enamel”
What this piece can’t prove
  • Small sample size (three T. rex teeth) limits assessment of variability across individuals or populations.
  • Measurements are from a single geological formation (Late Cretaceous Hell Creek Formation) and may not represent species-wide conditions.

1 further detail could not be confirmed from the summary.

2ex vivo animalCompare T. rex enamel-derived temperatures to coeval Hell Creek crocodilians to contextualize relative thermophysiology within the same paleoenvironment.clumped-isotope thermometry on crocodilian enamel (comparative)Expand

In plain English

Clumped-isotope (carbonate) measurements on tooth enamel from coeval Hell Creek Formation crocodilians yielded enamel-derived temperatures that were reported as significantly lower than those measured from T. rex teeth, supporting a between-taxon contrast in thermophysiology within the same paleoenvironment.

Key findings

  • Teeth of coeval Hell Creek Formation crocodilians yielded enamel-derived temperatures that were reported as significantly lower than those of T. rex.significantly lower (no crocodilian temperature values reported in abstract)
“Teeth of coeval Hell Creek Formation crocodilians yielded temperatures significantly lower than did those of T. rex.”
What this piece can’t prove

3 further details could not be confirmed from the summary.

3in silicoIntegrate enamel-derived temperatures with proxy paleotemperatures and model simulations to infer that T. rex maintained a body temperature higher than ambient environmental temperatures.in silico integration with proxy paleotemperaturesExpand

In plain English

The authors compared enamel clumped-isotope temperatures (T. rex mean 36.3 ± 2.5°C, n = 3 teeth) with proxy-derived paleotemperatures and with model simulations. That integrated analysis indicates T. rex maintained a body temperature higher than ambient environmental temperatures; model projections using these results suggest broad habitat suitability across much of the North American paleocontinent.

Key findings

  • Integration of enamel clumped-isotope temperatures with proxy paleotemperatures and model simulations indicates Tyrannosaurus rex maintained a body temperature higher than ambient environmental temperatures.
“Comparison with proxy-derived paleotemperatures and model simulations indicates that T. rex maintained a higher body temperature than its environment.”
What this piece can’t prove
  • Small empirical sample (three T. rex teeth) limits robustness of the organismal temperature estimate.
  • Proxy paleotemperature datasets may not be precisely coeval or spatially coincident with the sampled individuals.
  • Model simulations rely on assumptions (physiological parameters, environmental inputs) that introduce uncertainty into inferred temperature differentials and habitat projections.

2 further details could not be confirmed from the summary.

4in silicoUse the derived thermophysiology to project habitat suitability / geographic accessibility for T. rex across the North American paleocontinent, including colder/higher latitudes.habitat suitability modeling / spatial projection (in silico)Expand

In plain English

The authors report an in‑silico projection of habitat suitability for Tyrannosaurus rex across the Late Cretaceous North American paleocontinent based on derived body-temperature estimates; the projection indicates that most of the continent, including colder and higher latitudes, was potentially accessible to the species.

Key findings

  • Projected habitat suitability based on the derived body temperature shows that most of the North American paleocontinent, including colder and higher latitudes, were potentially accessible to T. rex.
“Projected habitat suitability for T. rex based on these results shows that most of the North American paleocontinent, including colder and higher latitudes, were potentially accessible to the species.”
What this piece can’t prove
  • The projection depends on integration of derived body-temperature estimates with paleoclimate/paleogeographic data and model simulations; results may be sensitive to those inputs and assumptions.

1 further detail could not be confirmed from the summary.

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Papers considered

The selected paper, plus nearby candidates.

PubMed, Europe PMC, Crossref · 15 candidate papers

Candidate

Figure 1: Methods for digitizing body outlines and calculating mass properties, for “maximum tail width” estimate for Tyrannosaurus rex .

Crossref

Source (opens in a new tab)

And 9 more candidates considered.