What T. rex Teeth Reveal About Its Body Temperature—and What an iPhone 18 Pro Teardown Reveals About Repairability

Two recent reports point to very different kinds of scientific and technical evidence. One uses the chemistry of fossilized teeth to estimate how warm Tyrannosaurus rex was when alive. The other examines the interior of Apple’s latest professional smartphone to see how easily it can be repaired.

The findings are not equally definitive. The T. rex research provides a new estimate of body temperature using a method designed to avoid a major limitation of earlier approaches. The iPhone 18 Pro teardown, meanwhile, identifies repair risks in a small sample of devices but does not establish how frequently those failures occur.

T. rex appears to have maintained a warm body

A team led by UCLA geochemists Randon J. Flores and Robert A. Eagle measured the body temperature of T. rex at about 36°C. That is close to the temperature of a modern elephant and considerably warmer than the image of a sluggish reptile that dominated popular culture for much of the last century.

The result is consistent with the view that T. rex was a warm-bodied, active animal. It does not, by itself, settle every question about dinosaur physiology or prove that all dinosaurs used the same metabolic strategy.

The study’s significance lies partly in the method used to obtain the estimate.

How teeth can act as a fossil thermometer

Tooth enamel forms inside a living animal. As it develops, the carbonate minerals in enamel incorporate different forms, or isotopes, of carbon and oxygen.

The researchers examined how often the heavy isotopes carbon-13 and oxygen-18 were bonded together in the enamel. These pairings are known as clumped isotopes. Their frequency depends on the temperature at which the mineral formed:

• At lower temperatures, heavy isotopes are more likely to occur together.
• At higher temperatures, they are distributed more randomly.
• The resulting pattern remains recorded in the mineral after fossilization, provided the enamel has retained the relevant chemical information.

This approach is called clumped isotope thermometry. Because it relies on the arrangement of isotopes within the tooth mineral, it avoids a major problem that affected some earlier temperature estimates.

Why earlier isotope measurements were difficult to interpret

Earlier attempts often used oxygen isotope ratios in fossil bones or teeth. Those measurements can reflect temperature, but they also depend on the isotopic composition of the water in the animal’s body.

For an extinct animal, the original water composition is much harder to reconstruct. A temperature estimate based on oxygen isotopes alone can therefore be affected by uncertainty about the water available to the animal.

Clumped isotope thermometry is designed to reduce that dependence on water composition. The enamel records the temperature at which it formed rather than simply reflecting the isotopic character of the water available to the animal.

What the finding does—and does not—show

A body temperature near 36°C is consistent with an internally regulated, warm-bodied animal. It also fits the modern scientific picture of T. rex as an active predator rather than a tail-dragging reptile that had to bask before moving.

Still, body temperature and metabolism are not identical concepts. A temperature measurement does not reveal every detail of how an animal produced or regulated heat. Nor does one species’ result automatically describe every dinosaur lineage.

Paleontologists have compared dinosaur physiology using several kinds of evidence, including:

• Bone microstructure
• Growth patterns
• Growth rates
• Geographic distribution
• Comparisons with living birds, mammals, and reptiles
• Chemical signatures preserved in fossil tissues

Those lines of evidence have not always pointed to one simple explanation. Some research has supported endothermy—the production of substantial internal heat, as in birds and mammals—while other work has suggested that different dinosaur groups may have used different thermal strategies.

The strongest conclusion is narrower: the chemistry of T. rex teeth indicates that its enamel formed at a warm body temperature, around 36°C.

The iPhone 18 Pro is more complicated inside than outside

The second report concerns a very different question: how the iPhone 18 Pro and iPhone 18 Pro Max can be repaired.

Externally, the phones retain the same dimensions and broadly the same appearance as the previous generation. Internally, however, the newer models include several substantial changes:

• Larger batteries
• A new A20 Pro chip
• A significantly larger vapor-cooling system
• Mechanical aperture blades in the main camera lens

The display-frame problem

According to the iFixit teardown described in the source material, removing the rear glass was relatively straightforward. That does not mean the phone is broadly easy to repair, because access to one component is only one part of the repair process.

The more serious issue involved the plastic frame behind the display. Of four iPhone 18 Pro and 18 Pro Max devices disassembled by iFixit, the frame broke on three. Apple does not sell that plastic frame as a separate replacement part. If it is damaged, the available repair path would require replacing the entire display module.

A display can reportedly be reattached without the plastic backing frame, but it would not sit flush with the phone’s body. That creates a practical distinction between reassembly and proper repair: a device may be capable of being put back together without being restored to its intended fit and finish.

The result is a warning, not a measured failure rate

Four devices are too few to establish how often the frame breaks during repair. The outcome could have been affected by several factors, including:

• The strength of the adhesive
• How much heat was applied
• The technician’s technique
• Differences between individual pieces of plastic
• Other variations in the teardown process

The source material also notes that the same plastic frame has appeared in earlier Pro models without causing comparable trouble in the reported pre-release repair work. That makes the teardown worth examining, but it does not establish that the iPhone 18 Pro has a predictable, high failure rate.

A separate teardown by tech reviewer Zach Nelson did not encounter the same breakage and resulted in a favorable assessment of the phone’s repairability after the display was removed. The conflicting outcomes reinforce the need for caution: teardown results can depend heavily on method and sample size.

What buyers and repair technicians should take from the teardown

For owners, the practical lesson is that a damaged screen may involve more than replacing the glass or display panel. If the supporting frame breaks during disassembly and cannot be purchased separately, the repair may become substantially more extensive.

For technicians, the reported breakage suggests that the display-removal procedure deserves particular care. The available information does not identify a guaranteed technique for avoiding damage, so it would be misleading to present one as established fact.

The teardown also highlights a broader repairability issue: parts availability matters as much as physical access. A phone can be disassembled without destroying it and still be difficult to repair economically if a small structural component is not sold separately.

Two kinds of evidence, two different levels of certainty

The T. rex and iPhone reports illustrate why evidence must be interpreted in context.

Subject	Evidence described	What it supports	Main limitation
Tyrannosaurus rex	Clumped isotope patterns in tooth enamel	An estimated body temperature of about 36°C	A temperature estimate does not explain every aspect of metabolism or dinosaur physiology
iPhone 18 Pro	Teardown of four devices, with three plastic-frame breakages reported	A potential repair risk around the display frame	The sample is too small to establish a failure rate

The fossil study uses a chemical signal preserved in biological tissue and applies a method intended to address a known problem in earlier measurements. The phone teardown is a hands-on observation of a small number of manufactured devices. Both are informative, but neither should be stretched beyond what the evidence can support.

For T. rex, the evidence strengthens the case for a warm-bodied animal. For the iPhone 18 Pro, it raises a repairability concern that needs broader testing before its frequency can be quantified.

Source

• Ars Technica, “T. rex teeth indicate it ran as warm as an elephant,” September 20, 2026: https://arstechnica.com/science/2026/09/t-rex-teeth-indicate-it-ran-as-warm-as-an-elephant/