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T. Rex Had a Body Temperature of 97 Degrees

33 points marojejian 1 hour ago 44 comments

gift link: https://www.nytimes.com/2026/09/16/science/trex-dinosaur-tem...

paper: https://www.science.org/doi/10.1126/sciadv.aeb7653

mepian 39 minutes ago | parent

I read the headline in Celsius and thought that they were a bit too hot.

micromacrofoot 38 minutes ago | parent

> Up until the early 2000s, dinosaurs were thought to be rather reptilian and therefore probably coldblooded, Dr. Wiemann said. That began to change as multiple lines of evidence from geochemistry studies and CT scans of fossils showed they were warm-blooded. Dr. Wiemann had previously found that T. rex had a fast metabolism, but she said the new study did an “exquisite” job of zeroing in on a precise body temperature.

> To take the body temperature of a long extinct, school-bus-size predator, scientists at the University of California, Los Angeles, used a clever geochemistry technique on fossilized teeth, including two from “Thomas,” a famous T. rex in the collection of the National History Museum of Los Angeles County.

fascinating

we've also learned more about the air at the time via teeth, https://nautil.us/the-data-in-a-dinos-smile-1229729

SoftTalker 13 minutes ago | parent

It intuitively makes sense. A cold-blooded creature of that mass would take a long time to properly warm up or cool down. Most modern cold-blooded animals are small, e.g. frogs, snakes, lizards. They can move into the sunlight or shade as needed and pretty quickly change temperature.

lioeters 37 minutes ago | parent

From the paper, that is: 36.3 ± 2.5°C.

orbital-decay 35 minutes ago | parent

Thanks, I thought it was almost boiling.

gibspaulding 31 minutes ago | parent

So 97.3 ± 4.5 °F for anyone else curious how the precision translates.

Galilyou 23 minutes ago | parent

Phew! Thank you! I feel for the ungodly fahrenheit again

nmoon 18 minutes ago | parent

Fahrenheit is the superior measure

WarmWash 15 minutes ago | parent

Better for day to day life, worse for science and engineering.

msm_ 13 minutes ago | parent

Is it really better for day to day life? I am certain that it only appears so because you're used to it. I think for day to day life they're both roughly equivalent.

Of course, for me Celsius is more natural and intuitive, but again - that's because I'm used to it.

antif 10 minutes ago | parent

100F is about peak summer heat; 0F is about peak winter chills. Works great for describing weather .. in various places.

konart 11 minutes ago | parent

>Better for day to day life

It is not.

rf15 14 minutes ago | parent

counterpoint: it doesn't matter, since you need to learn relevant boiling/freezing temperatures on both scales anyway.

As a european: F is the only american system that is easy to use and reason with (considering its 0-100 range is spanning the "doable" temp range of too-cold to too-hot), unlike other imperial systems for lengths and whatnot.

deagle50 11 minutes ago | parent

really is, and I grew up in celsius.

ChrisMarshallNY 34 minutes ago | parent

Wouldn't be surprised if the smaller raptors had even higher body temps.

layer8 27 minutes ago | parent

Seems sensible, given that birds have higher body temperatures.

hedgehog 5 minutes ago | parent

I didn't know this so I looked up the number for farm chickens, according to University of Kentucky (seems appropriate) they have a body temperature of "between 105°F and 107°F (40.6° and 41.7°C) ... Smaller chicken breeds have a higher body temperature than larger breeds"

https://afs.mgcafe.uky.edu/poultry/chapter-7-air-temperature

john_strinlai 32 minutes ago | parent

i know its the nytimes, so we can assume american units, but i find it sort of crazy that even throughout the body of the article it doesnt ever say "fahrenheit".

BugsJustFindMe 30 minutes ago | parent

It doesn't need to. Any other unit would be either insanely cold or insanely hot.

skrebbel 23 minutes ago | parent

Given that it’s a shouty headline in a major publication, that’s what I would have expected.

bthrn 29 minutes ago | parent

Common sense suggests that living creatures are likely not boiling when they have a mild fever.

john_strinlai 26 minutes ago | parent

i am not a paleontologist and there have been many extremely weird living creatures over the time earth has been around.

and as the sibling comment mentions, i am primed for science articles to be metric.

falserum 17 minutes ago | parent

I’m metric all the way, but if it would use metric, it still should unambiguously state: C

john_strinlai 15 minutes ago | parent

indeed! my "common sense" is to always state the units you're working with, no matter how obvious you think it is.

vojtapol 23 minutes ago | parent

Common sense would be using metric units in science-related article.

petcat 17 minutes ago | parent

Americans don't use Celsius when talking about their body temperatures, and that's who the audience is.

SoftTalker 16 minutes ago | parent

It's a US-based newspaper written for the general public. Common sense would say it's using US units.

ohyoutravel 32 minutes ago | parent

This is really interesting, worth a read. Wouldn’t be surprised if the even larger dinosaurs had even higher body temps!

laweijfmvo 31 minutes ago | parent

How do we know its body temperature was 97 degrees, and simply not the environment was 97 degrees?

pixl97 28 minutes ago | parent

What environment would stay at a constant 97 degrees?

surgi 26 minutes ago | parent

Europe this summer? /jk

cwmma 26 minutes ago | parent

If it was environmental then you'd expect it to fluctuate over time, but they also checked it against an animal they knew to be cold blooded, if it was environmental you'd expect them to be the same, but that animal was calculated by the same method to be colder.

altcognito 18 minutes ago | parent

They compared against crocodilian teeth and those teeth were at a different temperature. Crocodilian teeth are known to be at a similar temperature to their environment because they are known to be cold blooded.

It is correct to say that we don't know they were warm blooded, just that their body temps were likely the given observed temperature.

globular-toast 30 minutes ago | parent

Farenheit. So a little bit cooler than us.

moomoo11 29 minutes ago | parent

i will now believe this information until it becomes outdated in the future, at which point i will believe that information until it becomes outdated later

mindcandy 20 minutes ago | parent

Great! That's how knowledge is supposed to work.

partyficial 11 minutes ago | parent

that's not knowledge - that's just theory and belief.

you know, like religion.

strongwaddle 22 minutes ago | parent

'Hotter than a crocodile, cooler than a chickennnnn....'

is the opening line to a great song i'll never get to hear.

dpe82 12 minutes ago | parent

The slop generator's gotchu: https://suno.com/s/gT2YhaQyNdlkzgeU

p1mrx 7 minutes ago | parent

With the power of AI slop, you can hear anything: https://pmarks.net/posted_links/trex_ai.mp3

modzu 22 minutes ago | parent

id assumed as much since seeing jurassic park in 1996

kilroy123 8 minutes ago | parent

It's actually older, from 1993.

isomorphic 19 minutes ago | parent

https://archive.is/20260916181240/https://www.nytimes.com/20...

(Even the NY Times gift link requires a login.)

code_biologist 17 minutes ago | parent

Repost from a different thread: Related only topically, a 1hr YouTube talk I enjoyed a lot: "Hatchling T. rex and the Evolution of Vertebrate Parental Care" by Nick Longrich: https://www.youtube.com/watch?v=zd0dR2n9hLA

He's a paleontologist and the talk starts with some pretty interesting statistical analysis aiming to estimate T rex clutch sizes (66 eggs) and hatchling weights (1.5kg) as well as T rex parental care. It ends with looking at evolutionary history trends in increasing parental investment in radically different animals.

He talks a little slow, so a little playback speed bump won't go amiss.