saurisquio
Late Cretaceous, 65 million years ago
Colorado, Montana, New Mexico, Wyoming, Alberta
9.000Kg
5,2m
12m
Tyrannosaurus rex is the most famous dinosaur that ever lived, and also one of the worst explained. A good part of what “everyone knows” about it comes from the cinema and has been disproved for thirty years.
This page has what current palaeontology actually supports: how big it really was, the true force of its bite, why it had those arms, how fast it could move and what is known about its intelligence. With the studies behind each claim, so you can check them.
An adult T. rex was 12 to 13 metres long and weighed 6 to 9 tonnes, depending on the specimen and the estimation method. For a sense of scale: the length of a city bus and the weight of a loaded lorry.
Height is where most of the confusion sits. The measurement palaeontologists use is height at the hip, around 4 metres, because the animal walked with its body horizontal, the tail extended behind as a counterweight and the head out in front. That is the correct posture. The five-metre-plus figures still circulating come from the old reconstructions, the twentieth-century museum ones that stood it upright on its hind legs with the tail dragging on the ground. That posture never existed.
The most complete specimen known is called Sue, found in South Dakota in 1990 and now at the Field Museum in Chicago. It preserves around 90 % of the skeleton and measures 12.3 metres. Another specimen, Scotty, found in Saskatchewan, is the candidate for heaviest, with estimates around 8.8 tonnes.
Here the numbers genuinely are spectacular, and there is no need to inflate them.
The study by Bates and Falkingham (2012), which reconstructed the skull musculature by computer, estimated a bite force of 35,000 to 57,000 newtons at the back teeth. That is the most powerful bite measured or estimated in any land animal, living or extinct. A saltwater crocodile, which has the strongest bite among living animals, comes in at around 16,000.
There is also a lovely piece of physical evidence. Erickson and colleagues (1996) analysed bite marks on the fossilised pelvis of a Triceratops and calculated, from the depth of the punctures, a force of about 13,400 newtons from a single tooth.
That power let it do something almost no predator can: break bone and swallow it. Coprolites — fossilised droppings — have been found with crushed bone fragments inside.
As for teeth, it had 50 to 60, banana-shaped with serrated edges. The largest known is about 30 centimetres, but that includes the root: the crown showing above the gum was around 15. If you want to know how those jaws worked, we go into it in dinosaur teeth.
They were around a metre long with two fingers. On a twelve-metre animal they look like a design error. And they are, by a distance, what children ask about most in the park.
The first surprise is that they were not weak. The humerus is thick and the muscle attachment scars are enormous for its size: estimates suggest each arm could lift something in the order of 200 kilos. A small arm, but a weightlifter's.
What it used them for is still debated, and there are three main hypotheses. Holding prey down while it bit. Helping it get up from lying down, which at eight tonnes is not trivial. Or a function related to mating.
There is a fourth idea, more recent and rather elegant, proposed by Kevin Padian in 2022: that the arms shrank precisely to get them out of the way. If several tyrannosaurs fed on the same carcass, long arms would sit within reach of the others' jaws, and a 35,000-newton bite does not forgive. Short arms, fewer amputations.
What is clear is the overall logic: all of this animal's specialisation went into the head. A metre-and-a-half skull with that musculature needs compensating somewhere, and the arms were what got sacrificed.
This is the answer that has changed the most, and the hardest to accept for anyone who grew up with the films.
An adult T. rex could not run. The study by Sellers and colleagues (2017) simulated the complete skeleton under running forces and found that the leg bones would have fractured before it reached high speeds. It is not that it did not want to: the physics would not allow it. Its top speed comes out at around 20 km/h, a very brisk walk with no aerial phase, no moment when both feet leave the ground at once.
A later study by Van Bijlert and colleagues (2021) calculated its preferred walking speed from the mechanics of the tail, which worked like a spring: about 4.6 km/h. Almost exactly the pace a person walks at.
This does not make it slow for its league. At twenty an hour it caught the large herbivores of its ecosystem without difficulty, and they were no sprinters either. And the juveniles were fast: lighter, with proportionally longer legs, they filled a different ecological role from the adults. On who really could run, see the fastest dinosaur discovered so far.
If speed is where it comes off worst, the senses are where it dominates.
It had enormous olfactory bulbs relative to the brain, among the largest of any known theropod. It could smell over very long distances, which is how you locate prey and carcasses alike.
And it had binocular vision, uncommon among dinosaurs. Its eyes faced forward rather than sideways, which gives depth perception and lets an animal judge distance. Kent Stevens (2006) estimated a binocular field of around 55 degrees, wider than a modern hawk's.
That combination — a scavenger's nose and a hunter's eyes — is the profile of a capable opportunistic predator, which is what the evidence supports.
This is one to be careful with, because it is a live topic with two opposing positions.
In 2023, the neuroscientist Suzana Herculano-Houzel published a neuron-count estimate suggesting T. rex had something like three billion neurons in the telencephalon, in the range of a baboon. That would imply abilities such as tool use or cultural transmission. The story went round the world.
In 2024, a large team led by Kai Caspar published a detailed rebuttal, arguing that the endocranial volume had been overestimated (much of the cavity was taken up by sinuses and blood vessels, not brain) and that the extrapolation methods were not valid. Their conclusion places T. rex cognition in the range of living reptiles, crocodiles and large lizards.
The majority position today is the second one. The honest way to put it: it was clever for a reptile, with a large brain compared with other dinosaurs its size and very well developed sensory areas. That is a long way from solving problems like a primate.
The short answer: probably some, and probably not the ones you are picturing.
In favour are its relatives. Yutyrannus, a nine-metre Chinese tyrannosauroid, was found with filamentous down preserved, as was the smaller Dilong. If close relatives of a decent size had feathers, it is reasonable to think the lineage kept them.
Against, there is direct evidence from T. rex itself. Bell and colleagues (2017) described skin impressions from several parts of the body — neck, hip, tail — and all of them show scales, not feathers.
The reconstruction that reconciles the two is the one most palaeontologists work with today: hatchlings and juveniles with down, lost as they grew, and largely scaly adults, perhaps with some feathers left on the back or neck. It makes thermal sense: an eight-tonne animal retains heat without help. The whole subject is in feathered dinosaurs.
Meat, and a lot of it. Its documented prey includes the large herbivores of its ecosystem: Triceratops and hadrosaurs such as Edmontosaurus.
And the proof that it hunted actively — rather than only scavenging — is one of the finest things in palaeontology: Edmontosaurus vertebrae have been found with a T. rex tooth embedded and healed bone grown around it. Bone only regenerates if the animal survives. That hadrosaur was bitten by a living T. rex, escaped and healed.
That said, it also ate carrion when it found it, as every large predator alive today does. The "hunter or scavenger" debate of the 1990s is closed: it was both, which is the normal answer. More on prehistoric diets in what dinosaurs ate.
Adult skeletons turn up covered in scars, and many of the marks on the skull match the teeth of another T. rex. They fought each other, probably over territory, food or mates. Sue, the Chicago specimen, shows broken and re-fused ribs and significant jaw damage.
On whether they hunted in groups, the evidence is suggestive but not conclusive: there are sites with several individuals together, which could indicate social behaviour or simply that they died in the same place.
And one open question you can look at in the park itself. Nanotyrannus was described as its own genus of small tyrannosaur, but a substantial part of the community holds that those fossils are juvenile T. rex. We have both animals on the route, so you can compare one with the other: it is one of those arguments that makes far more sense standing in front of the two than read on a page.
The first skeleton was found by Barnum Brown in 1902, in the Hell Creek Formation of Montana. Three years later, in 1905, Henry Fairfield Osborn gave it the name we know: Tyrannosaurus rex, "tyrant lizard king".
Around fifty specimens have been recovered since, a very high number for a large predator. That abundance is what makes its growth possible to study: we know it went through a brutal adolescent growth spurt, gaining something like 600 kilos a year between the ages of 14 and 18, and that it rarely passed 30.
And at the end of it all comes the asteroid. T. rex was one of the last great dinosaurs on Earth: it was alive on the day of the impact that closed the Cretaceous, 66 million years ago. The full story is in how the dinosaurs went extinct.
Reading that it was twelve metres long is one thing. Standing underneath it is another.
At Dinosaurland we have a life-size animatronic Tyrannosaurus rex: it has sensors that trigger when someone comes close, and then it moves its head, opens its mouth and roars. It is the piece people stop in front of longest, and the one that produces the reaction parents end up filming on their phones.
It stands on an open-air trail through pine woods with more than 100 life-size dinosaurs from around 40 species, in Porto Cristo, Mallorca. You can compare it with the Triceratops it hunted, with the Velociraptor — far smaller than the films led everyone to believe — and with Spinosaurus, the other carnivorous giant. Pages for every species are in the dinosaur section.
🎟️Come and see the T. rex up close. Tickets at tickets.dinosaurland.es, with €1 off per ticket when you book online. Prices and conditions in tickets, prices and how to book; opening days in dates and opening times.
Got a small palaeontologist at home? We have a Tyrannosaurus Rex colouring sheet as a PDF, ready to print.
How big was the T-Rex?
12 to 13 metres long and around 4 metres tall at the hip. It walked with its body horizontal and its tail extended behind, not upright: the old reconstructions standing it on its hind legs with the tail on the ground are wrong.
How much did Tyrannosaurus rex weigh?
Between 6 and 9 tonnes depending on the specimen. Scotty, found in Saskatchewan, is the candidate for heaviest, with estimates around 8.8 tonnes.
Why did the T-Rex have such short arms?
Nobody knows for certain, but they were around a metre long and they were not weak: each could lift something in the order of 200 kilos. The main hypotheses are holding prey, helping it get up off the ground, and mating. A 2022 proposal suggests they shrank so they would not sit within reach of other tyrannosaurs' jaws when feeding in a group.
How fast could the T-Rex run?
It could not run. The Sellers study (2017) concludes that running would have fractured its leg bones. Its top speed was around 20 km/h, a fast walk with no aerial phase, and its preferred walking speed about 4.6 km/h, similar to a person's.
Was the T-Rex intelligent?
It was clever for a reptile. A 2023 study placed it at primate levels, but a 2024 rebuttal showed the brain volume had been overestimated and returned its cognition to the range of crocodiles and large living lizards. That is the majority position today.
How strong was its bite?
Between 35,000 and 57,000 newtons according to muscle reconstructions, the strongest of any known land animal. It could break bone and swallow it: fossilised droppings have been found with crushed fragments inside.
How many teeth did it have and how big were they?
Between 50 and 60, serrated and banana-shaped. The largest known reaches 30 centimetres including the root; the part visible above the gum was about 15.
What did Tyrannosaurus rex eat?
Large herbivores from its ecosystem, such as Triceratops and hadrosaurs. Hadrosaur vertebrae have been found with a T. rex tooth embedded and healed bone around it, which proves it hunted live prey. It also ate carrion when it found it.
Did the T-Rex have feathers?
Probably down as a hatchling and juvenile, and scaly skin as an adult. Its relatives Yutyrannus and Dilong were found with feathers, but the T. rex skin impressions described in 2017 show scales.
When and where did it live?
In western North America, 68 to 66 million years ago, at the end of the Cretaceous. Its fossils turn up in Montana, Wyoming, Colorado, South Dakota, New Mexico, Alberta and Saskatchewan.
How long did a T-Rex live?
It rarely passed 30 years. It grew very fast through adolescence, putting on something like 600 kilos a year between 14 and 18.
Can you see a life-size T-Rex in Mallorca?
Yes. At Dinosaurland, in Porto Cristo, there is a life-size animatronic Tyrannosaurus rex that moves and roars when you approach, on a trail with more than 100 dinosaurs.
Perhaps that is why it keeps winning. A hundred and twenty years after Barnum Brown pulled the first bone out of Montana, nobody has taken the name off it.
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