T. rex Facts for Kids
Meet the “tyrant lizard king”: a giant with banana-sized teeth, a bone-crushing bite and the most famous tiny arms in history.
What was T. rex?
Tyrannosaurus rex was a huge meat-eating dinosaur that lived about 68 to 66 million years ago, in what is now western North America. It was about 12 metres long and weighed around 8 tonnes, which is heavier than a big bull elephant.
Its name means “tyrant lizard king”. Scientists usually shorten it to T. rex. It was one of the very last dinosaurs, alive right up until the asteroid hit Earth 66 million years ago. It shared its world with the three-horned Triceratops, and the two of them really did meet.
📏 How long was T. rex?
Lay them all end to end and see how they measure up.
- T. rex12 m
- A school busabout 12 m
- A family carabout 4.5 m
- You, lying downabout 1.2 m
Sizes are for a big grown-up T. rex. Young ones were much smaller and grew very fast.
Teeth like steak knives
A T. rex had about 60 teeth. The biggest part you could see, called the crown, was as long as a banana. With the root that sat hidden inside the jaw, a whole tooth could be 30 centimetres long.
Each tooth had tiny bumps along its edges called serrations, just like a steak knife. T. rex had the hardest bite of any land animal ever measured. Scientists say it was like having an elephant sit on you, pushed through one single tooth. It could crush bone, and we know because chewed-up bone turns up in its fossil poo!
How a T. rex was built
- It walked with its back held level and its tail straight out behind, like a seesaw. Old pictures showing it standing upright, dragging its tail, are wrong.
- Its tiny arms were about as long as a child’s whole body, thick and strong, with two clawed fingers.
- It had a big part of the brain for smelling, so it probably had an excellent nose.
- Each foot had three big toes on the ground and a small dewclaw higher up. See how they fit in dinosaur footprints.
Why were T. rex arms so small?
This is one of the biggest puzzles in the dinosaur world, and the honest answer is: nobody has worked it out yet. The arms were short, but they were not weak. They had thick bones and big muscles.
Scientists have suggested many ideas. Maybe they helped it hold on to prey, or push itself up off the ground after a rest. Maybe they simply shrank because the giant head and jaws did all the work. Every idea has problems, so the mystery is still open. Maybe you will be the one to solve it!
Fun T. rex Facts
Its biggest teeth were the size of bananas.
The crown, the part above the gum, was banana-sized. The whole tooth with its root was about 30 centimetres long.
We know it crunched bones because of its fossil poo.
Fossil droppings are called coprolites. Some T. rex coprolites are full of broken bits of bone from the animals it ate.
It probably could not sprint like in the movies.
Scientists still argue about its speed. Some computer studies suggest a fully grown T. rex was too heavy to truly run, and moved in a fast, long-legged walk instead.
Teenage T. rexes grew super fast.
By studying growth rings inside fossil bones, scientists found that a young T. rex could put on about 2 kilograms a day during its biggest growth spurt.
Nobody has ever found a whole T. rex egg.
Scientists can guess its size from fossil babies and from the eggs of its relatives, but a complete T. rex egg is still waiting to be discovered.
Science words to know
- Fossil
- The remains or traces of a living thing from long ago, preserved in rock.
- Carnivore
- An animal that eats meat.
- Serrated
- Having a row of tiny bumps along an edge, like a bread knife.
- Coprolite
- Fossil poo! It shows scientists what an animal ate.
Quick quiz!
0 / 31. What does the name Tyrannosaurus rex mean?
2. How did T. rex hold its body when it walked?
3. Why were T. rex arms so small?
Questions kids ask
How big was a T. rex?
A big adult T. rex was about 12 metres (40 feet) long, about as long as a school bus, and weighed around 8 tonnes.
What did T. rex eat?
T. rex was a carnivore. It ate other dinosaurs, including big plant-eaters like Triceratops and duck-billed dinosaurs. Find out how scientists know in what did dinosaurs eat.
How many teeth did T. rex have?
About 60, and it kept replacing them all its life. The biggest crowns were the size of a banana.
When did T. rex live?
About 68 to 66 million years ago, at the very end of the age of dinosaurs. That is long after Brachiosaurus, which lived about 150 million years ago.
Did T. rex have feathers?
Skin fossils show T. rex had tiny pebbly scales, each smaller than a grain of rice. It may have had a few feathers too. Read more in did dinosaurs have feathers.
T-rex Foot Puzzle
Rebuild a giant T. rex foot bone by bone. Start with the tall ankle bone, then twist each toe and claw into place.
✔ The whole Dinosaur Wing is free to play
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