Dinosaur Facts for Kids

Dinosaur quick facts

• The asteroid that ended the age of the dinosaurs probably came from beyond Jupiter, a 2024 study found.
• Fossil fish show that the asteroid struck in spring in the northern half of the world.
• Around 50 new kinds of dinosaur are named every year (2024), roughly one a week.
• The first fossils accepted as dinosaur eggs, found in 1923, were credited to the wrong dinosaur for about 70 years.
• Some sauropod neck bones show signs of a disease that still affects birds today.

What makes an animal a dinosaur?

Dinosaurs were a group of reptiles, but they did not stand like other reptiles. Their back legs went straight down under their bodies, a bit like the legs of a horse. Scientists call this an upright stance.

Lizards stand in a different way. Their legs stick out to the side and then bend down, which is called a sprawling stance. Watch a lizard such as the Komodo dragon walk and you can see its legs splayed out.

Standing upright gave dinosaurs an advantage. They used less energy to move than sprawling reptiles, and their legs could hold up more weight. This is the main feature that sets dinosaurs apart from every other reptile.

Dinosaurs shared a few other features too:

• They laid eggs, like other reptiles.
• They lived on land, not in the sea. The only exceptions are a few birds, such as penguins.
• Their skulls had a hole between each eye socket and nostril, and two more holes behind each eye.
• Strong jaw muscles passed through those holes, so dinosaurs could open their jaws wide and clamp down hard.

Birds are living dinosaurs

Here is the fact that surprises most people. Dinosaurs are not all extinct. Birds are dinosaurs, and they are the one group that survived when all the others died out 66 million years ago.

So a pigeon on a windowsill is a dinosaur. So is a robin, an owl or a hen. From a hen’s egg to an ostrich egg, every bird’s egg is a dinosaur egg. Even your breakfast egg counts.

Scientists did not always know this. In 1964, a palaeontologist called John Ostrom studied a new dinosaur named Deinonychus. A palaeontologist is a scientist who studies fossils. Ostrom noticed that its hands and hips looked a lot like a bird’s, and he suggested that birds came from dinosaurs.

At the time, that idea was highly controversial. By the late 1980s, more scientists were starting to accept it. Then feathered dinosaurs were found in China in the 1990s, and that finally settled the argument for most of them.

When dinosaurs lived

The first dinosaurs appeared about 245 million years ago, and the last non-bird dinosaurs died out 66 million years ago. Between those two dates lie about 180 million years. That is a very long time.

Numbers this big are hard to picture. If you counted one number every second, day and night without stopping, it would take you more than two years to reach 66 million. The age of the dinosaurs lasted nearly three times as long as all the time since it ended.

Scientists call this stretch of time the Mesozoic Era. An era is a very long chapter in Earth‘s history. The Mesozoic is split into three periods: the Triassic, the Jurassic and the Cretaceous.

Period	Millions of years ago	What the world was like	Dinosaurs living then
Triassic	252 to 201	All the land joined in one supercontinent, Pangaea. Hot and dry, with big deserts and no ice caps	The first dinosaurs, such as Coelophysis
Jurassic	201 to 145	Pangaea split in two. Wetter, with ferns, horsetails and tall conifer forests	Long-necked giants such as Diplodocus and Brachiosaurus, and Stegosaurus
Cretaceous	145 to 66	The land broke into continents we would recognise, in different places. Flowering plants and bees spread	Tyrannosaurus, Triceratops and the giant titanosaurs

Dinosaurs did not all live at the same time. The world changed a great deal over those 180 million years. In the Triassic, you could have walked from one side of the land to the other without crossing an ocean. Toward the end of the period, earthquakes and huge volcanic eruptions began to split Pangaea apart. That was the birth of the North Atlantic Ocean.

Nobody knows for sure which dinosaur came first. Fossils of an animal called Nyasasaurus suggest it may have been one of the very first dinosaurs, but scientists are still not certain. The search goes on.

The Triassic ended with a mass extinction, a time when huge numbers of living things died out. Its causes are still hotly debated. Many large land animals were wiped out, but the dinosaurs survived. That gave them the chance to evolve into a huge variety of shapes and sizes over the next 135 million years.

In the Jurassic, ferns and horsetails grew over huge areas. Some of that ancient greenery was buried and slowly turned into the fossil fuels people mine today.

The name Cretaceous comes from creta, the Latin word for chalk. A lot of chalk formed in that period, from the skeletons of tiny sea algae that piled up on the seabed. Britain’s White Cliffs of Dover are made of chalk from the Late Cretaceous, right at the end of the age of the dinosaurs. You can still see them today.

Types of dinosaur: the six main groups

Palaeontologists sort dinosaurs into groups of close relatives. Six groups are the best known. Theropods walked on two legs and include every big meat-eater. The other five groups were all plant-eaters.

Group	What they looked like	What they ate	Example
Theropods	Walked on two legs. Many had feathers, and birds belong to this group	Mostly meat	Tyrannosaurus rex, Megalosaurus
Sauropods	Enormous, with small heads, long necks and long tails. Walked on four legs	Plants	Diplodocus, Patagotitan
Ornithopods	Often walked on two legs but could drop onto four. Some had duck-like beaks	Plants	Iguanodon, Maiasaura
Ceratopsians	Horns on the face and a bony frill at the back of the skull	Plants	Triceratops, Protoceratops
Stegosaurs	Two rows of tall plates along the back and spikes on the tail	Plants	Stegosaurus
Ankylosaurs	Low and wide, covered in bony armour. Some had a club on the tail	Plants	Ankylosaurus

Plant-eating animals are called herbivores, and meat-eaters are called carnivores. The best-known carnivore is Tyrannosaurus rex, a theropod that lived in the Late Cretaceous in what is now the USA.

Sauropods were the true giants. They walked on four pillar-like legs and had long necks and even longer tails. Diplodocus, Apatosaurus and Brachiosaurus were all sauropods, and they are some of the largest animals ever to walk on Earth.

Ceratopsians such as Triceratops had some of the strangest heads of any animal. Triceratops and its close relatives had frills that could be more than two metres (6.5 feet) long. Their skulls are the longest known of any land animal, living or extinct.

What were the frills for? Nobody can say for certain. Scientists used to think they protected the neck from the bites of big meat-eaters. But some frills are very thin and don’t seem strong enough. Many scientists now think they were for showing off. They may have been brightly coloured, and used to impress mates or warn off rivals.

The biggest and smallest dinosaurs

The biggest dinosaurs of all were titanosaurs, a family of sauropods. Sauropods reached their largest sizes in the Cretaceous, and the titanosaurs were the largest of them.

One of the most famous titanosaurs is Patagotitan. It was about 37.5 metres (123 feet) long. That is longer than three double-decker buses parked end to end. Nothing on land today comes close.

Triceratops was big too. It was the largest of the ceratopsians, about twice as long and twice as heavy as an African elephant. Its frill alone could be almost a metre across.

Not every dinosaur was a giant, though. Microraptor was only about the size of a chicken.

Living dinosaurs can be smaller still. A sparrow is a dinosaur, and it would fit in the palm of your hand. So the dinosaur family runs all the way from a bird you could hold to an animal longer than three buses.

What dinosaurs ate

Teeth are one of the best clues to a dinosaur’s diet. Sharp, pointed teeth usually mean meat. Teeth made for grinding or stripping leaves usually mean plants. Some plant-eaters had very unusual mouths, as you can see in our guide to Nigersaurus.

Plant-eaters had plenty to choose from. In the Jurassic there were ferns, horsetails and forests of tall conifer trees, such as sequoias and monkey puzzles. This rich supply of food helped the huge sauropods to evolve.

By the end of the Cretaceous, flowering plants had become a much more common part of Earth’s plant life. Bees appeared in that period too, and they helped flowering plants to spread.

Most theropods ate other animals. Deinonychus, for example, was a small, fast, two-legged predator. Its fossils helped to change the old idea that all dinosaurs were slow and clumsy.

Sometimes a fossil shows what an animal really ate. Baryonyx had a skull and teeth suited to catching fish. It may have hooked fish out of rivers with its enormous claws, a bit like a grizzly bear catching salmon.

But scientists found something else inside one Baryonyx skeleton. Along with fish scales, the part thought to be its stomach held bones of an Iguanodon. So its diet was probably more varied than scientists first thought. Clues like these are called gut contents.

Feathers, eggs and babies

We now know that some dinosaurs that were not birds had feathers. The first clear proof came from China in the 1990s. A fossil of a small dinosaur called Sinosauropteryx showed the marks of feather-like structures around its body.

There had been an earlier clue. In 1861, the first skeleton of Archaeopteryx was dug up in Germany. It had clear marks of feathers, so it was described as one of the first birds. But later fossils showed it also had teeth, clawed fingers and a long bony tail. No living bird has any of those.

Archaeopteryx was found just two years after Charles Darwin published his famous book On the Origin of Species. Darwin’s supporter Thomas Huxley was one of the first people to notice how much Archaeopteryx looked like some meat-eating dinosaurs. The Natural History Museum in London looks after one of these fossils, with its feather marks still clear.

Every dinosaur hatched from an egg. In 1923, scientists from the American Museum of Natural History found the first fossils widely accepted as dinosaur eggs, in the Gobi Desert in Mongolia. At first they were thought to belong to Protoceratops, a plant-eater often found in the area. In the 1990s, scientists realised they more likely belonged to Oviraptor-like animals. The mix-up lasted about 70 years.

In the 1980s, palaeontologists in Montana, in the USA, dug up nests of a duck-billed dinosaur called Maiasaura. Eggs, hatchlings and adults were found together. These fossils were the first strong evidence that dinosaurs fed and cared for their young.

As many as 14 nests were found close together at one site, now called Egg Mountain. Because of this, some scientists think Maiasaura may have nested in colonies.

Another fossil shows a dinosaur called Citipati sitting on top of its nest of eggs. It suggests that some dinosaurs were protective parents, just as many birds are today.

How dinosaur fossils form

A fossil is physical evidence of a prehistoric animal or plant. Almost everything we know about extinct dinosaurs comes from fossils, so it helps to know how they form.

Most dead animals simply rot away. To become a fossil, a body has to be covered quickly by layers of mud, sand or silt. Dinosaur fossils are usually found in mudstones and sandstones. These rocks formed from mud and sand laid down by rivers, lakes and sand dunes. Here is how it happens:

• A dinosaur dies, and its body is quickly buried by mud, sand or silt.
• More layers settle on top and are pressed down hard. Over time they turn into sedimentary rock.
• Bit by bit, parts of the bones and teeth are replaced by minerals, which turns them to stone. For big dinosaur bones, this can take thousands of years.
• Millions of years later, the rock may be exposed at the surface, where someone can find the fossil.

There are two main kinds of fossil. Body fossils are the remains of the animal itself, such as bones, claws and teeth. Trace fossils are signs an animal left behind. These include footprints, eggs and nests, prints of skin or feathers, and even fossilised poo, which is called coprolite.

Dinosaur fossils turn up wherever there are rocks of the right age and type. That means rocks from about 240 to 66 million years ago. So far, the most dinosaur fossils have come from the USA, Canada, China and Argentina. Many have also been found in the UK, Brazil, Germany, South Africa and India.

To choose where to dig, palaeontologists use geological maps. These show which layers of rock lie in an area, and what age they are. That tells them whether dinosaur fossils could be hidden underground. A good map saves a lot of digging.

How scientists date and study fossils

You cannot tell how old a fossil is just by looking at the bone. Instead, scientists look at the rock it was found in. The rock holds the answer.

Sedimentary rock builds up in layers, like sheets of paper piling up on a desk. The layers at the bottom were laid down first, so they are usually the oldest. A fossil in a deeper layer is normally older than one in a layer above it. Depth acts a little like a clock.

Some fossils work like date stamps. They are called index fossils. They come from animals that were very common but lived for only a short stretch of time. When the same index fossil turns up in rocks in two different places, those rocks must have formed at about the same time.

Ammonites make excellent index fossils. They were sea creatures with coiled shells that evolved quickly and lived all over the world. Long ago, people thought ammonite fossils were coiled snakes that had turned to stone.

Fossils can show much more than what a dinosaur looked like. They can reveal what it ate, from gut contents. They can show broken bones from fights or other injuries, and even signs of disease. Footprints show where an animal was at one moment in time, and how it moved around its world.

Some of the most useful fossils are tiny. Any fossil less than one millimetre across is called a microfossil, and scientists study them under a microscope. They can be whole creatures, or scraps such as bits of bone and tiny teeth.

The first dinosaurs to be named

People found dinosaur bones for thousands of years before anyone knew what they were. Native Americans and other Indigenous peoples in Central Asia and South America even told stories about creatures based on the fossils they found.

The scientific story began in England. Around 1818, William Buckland, a clergyman at the University of Oxford, began studying some large fossils found around Oxfordshire. On 20 February 1824, at a meeting of the Geological Society of London, he formally introduced the animal they came from. He called it Megalosaurus.

Megalosaurus was the first dinosaur ever described by scientists. Dinosaur science had begun. Buckland thought it was a type of giant lizard that walked on four legs. It was later named Megalosaurus bucklandii in his honour.

A year later, in 1825, a second giant reptile was described. The first clues were teeth found at the side of a road by Mary Ann Mantell and her husband, Dr Gideon Mantell. The teeth looked like much bigger versions of the teeth of a living iguana. So the animal was named Iguanodon, which means “iguana tooth”.

Iguanodon was a big surprise. It was the first giant prehistoric reptile found to eat plants. At the time, people thought reptiles ate mainly meat or insects.

There was still no word for these animals. Then, in 1842, 18 years after Megalosaurus was described, the scientist Richard Owen grouped them under a new name: Dinosauria. It comes from Greek words often translated as “terrible lizard”, and it gave us the word dinosaur.

By the 1870s, the hunt had moved to North America. Two American palaeontologists, Othniel Charles Marsh and Edward Drinker Cope, became bitter rivals. Their rivalry soon turned very nasty. They spied on each other, stole fossils and even destroyed some to get ahead. Their feud became known as the Bone Wars.

The Bone Wars ruined both men’s reputations, but they gave the world many near-complete skeletons. Some of the most famous names come from this time, including Stegosaurus, Triceratops, Allosaurus, Diplodocus and Brontosaurus.

How many kinds of dinosaur are there?

Scientists have now named hundreds of kinds of dinosaur, and the list is growing fast. In January 2024, the Natural History Museum in London said that around 50 new dinosaurs are named around the world each year, on average. That is roughly one new dinosaur every week.

Why are so many being found now? The museum gave three reasons. Scientists are searching in parts of the world that were never explored before. There are more dinosaur experts than there used to be. And new technology in the lab lets them study fossils in more detail than ever.

Not every new dinosaur comes out of the ground. Some come from old fossils that have sat in museum collections for years, until someone looked again and realised they were something new.

This means no list of dinosaurs is ever finished. The year 2024 also marked 200 years since Megalosaurus was named, and in those two centuries the count has grown from one to hundreds. It will keep on growing.

What happened to the dinosaurs 66 million years ago

Sixty-six million years ago, a giant asteroid smashed into Earth. An asteroid is a large rocky object that travels around the Sun.

It struck what is now Mexico, and left a crater 150 kilometres (93 miles) wide. That is about twice the distance from London to Brighton. It is called the Chicxulub crater, and it is the second-largest crater on Earth.

The asteroid itself may have been up to 15 kilometres (9 miles) across. That is wider than Mount Everest is tall. It fell at a steep angle and instantly vaporised everything nearby. The whole world was plunged into what scientists call a nuclear winter, a long spell of cold and gloom.

Every dinosaur died out except the birds. The age of the dinosaurs, and the whole Mesozoic Era, was over. It had lasted about 180 million years.

How do we know an asteroid did it? The first clue came in the late 1970s. A father and son, Luis and Walter Alvarez, found lots of a metal called iridium in rocks from the very end of the Cretaceous. Iridium is rare in Earth’s rocks but common in asteroids. Their idea met resistance at first. Over the next ten years or so, it was gradually accepted.

The crash also turned rock into tiny beads of glass, called spherules, and scattered them across the world. Some of them got stuck in the gills of dying fish. Growth lines in those fish bones can be read a bit like the rings in a tree trunk. They show that the asteroid hit in spring in the northern half of the world. Even the season is known.

There was one big unanswered question: where did the asteroid come from? In the mid-2000s, some scientists suggested it came from a family of asteroids in the main asteroid belt, between Mars and Jupiter. Later evidence ruled that out.

In August 2024, a new study gave an answer. Scientists tested rocks from Spain, Italy and Denmark that formed at the time of the impact. They measured tiny amounts of a rare metal called ruthenium. Its chemical fingerprint matched a kind of space rock called a carbonaceous chondrite. That was a big clue.

That kind of space rock can only come from asteroids found beyond the planet Jupiter. So the asteroid that ended the dinosaurs was a visitor from the outer solar system. Carbonaceous chondrites are also one of the oldest known types of asteroid, formed billions of years ago.

Not everyone has always agreed that an asteroid was to blame. Other ideas have been put forward, including huge volcanic eruptions. The 2024 study adds weight to the asteroid, because the ruthenium fits an asteroid strike much better than a comet or massive eruptions. Scientists still hope to work out exactly which type of asteroid it was.

Three things people get wrong

1. Pterosaurs, plesiosaurs and ichthyosaurs were not dinosaurs. Pterosaurs were flying reptiles, not dinosaurs. Plesiosaurs and ichthyosaurs were reptiles that lived in the sea. None of them had the upright stance that makes a dinosaur a dinosaur.

Pterosaurs were close cousins, though. They belong to a bigger group of reptiles called archosaurs, along with dinosaurs and crocodiles. Dimetrodon, with the tall sail on its back, was not a dinosaur either, and it lived even longer ago. The sabre-toothed cat and the woolly mammoth were not reptiles at all. They were mammals, and they lived long after the dinosaurs had gone.

2. People never lived alongside the dinosaurs. Films and cartoons sometimes show cave people running from dinosaurs, but it never happened. The last non-bird dinosaurs died out 66 million years ago. The first modern humans appeared many millions of years later. In one way, though, we do share the planet with dinosaurs. Every time you hear a bird sing, you are listening to one.

3. Dinosaurs were not giant, slow, scaly lizards. When Megalosaurus was first described, it was pictured as a huge lizard on four legs. We now know that picture was wrong in several ways. Lizards sprawl, but dinosaurs stood upright. Deinonychus, found in 1964, was a small, fast hunter, not a lumbering giant. Microraptor was the size of a chicken. And fossils from China show that some dinosaurs were covered in feathers, not scales.

Frequently asked questions

Are birds really dinosaurs?

Yes. Birds are living dinosaurs, the only group of dinosaurs that survived when an asteroid hit Earth 66 million years ago.

When did dinosaurs live?

Dinosaurs first appeared about 245 million years ago, in the Triassic Period. The non-bird dinosaurs died out 66 million years ago, at the end of the Cretaceous Period.

What killed the dinosaurs?

An asteroid up to 15 kilometres wide hit what is now Mexico 66 million years ago, leaving the 150-kilometre Chicxulub crater. A 2024 study found that the asteroid came from beyond Jupiter.

What was the first dinosaur ever named?

Megalosaurus was the first dinosaur described by scientists. William Buckland introduced it at the Geological Society of London on 20 February 1824.

How many kinds of dinosaur are there?

Scientists have named hundreds of kinds of dinosaur, and the number keeps rising. In 2024 the Natural History Museum said around 50 new dinosaurs are named each year.

Did people live at the same time as dinosaurs?

No. The non-bird dinosaurs died out 66 million years ago, many millions of years before the first modern humans appeared.

Were pterosaurs dinosaurs?

No. Pterosaurs were flying reptiles related to dinosaurs, but not dinosaurs. Sea reptiles such as plesiosaurs and ichthyosaurs were not dinosaurs either.

Sources

• Natural History Museum: What are dinosaurs? — the upright stance and skull features that define a dinosaur, eggs, birds as living dinosaurs, Microraptor’s size, and why pterosaurs, plesiosaurs, ichthyosaurs and Dimetrodon were not dinosaurs
• Natural History Museum: When did dinosaurs live? — dinosaurs from about 245 to 66 million years ago, the dates and worlds of the Triassic, Jurassic and Cretaceous, Nyasasaurus, Jurassic plants and sauropods, Patagotitan’s length, chalk, and humans arriving millions of years later
• Natural History Museum: The seven greatest dinosaur discoveries of the last 200 years (2024) — Megalosaurus in 1824, Iguanodon and the Mantells, Owen’s word dinosaur, Archaeopteryx, the Bone Wars, the 1923 eggs, Maiasaura nests, Deinonychus and Sinosauropteryx
• Natural History Museum: What is a fossil? (2023) — how fossils form, body and trace fossils, sedimentary rock, geological maps and William Smith, index fossils and ammonites, Baryonyx’s gut contents, Citipati on its nest, disease in sauropod bones and microfossils
• Natural History Museum: Dinosaur-killing Chicxulub asteroid came from the edge of the solar system (2024) — the Chicxulub crater and asteroid size, the Alvarez iridium evidence, spherules and the springtime impact, and the 2024 ruthenium study pointing to an asteroid from beyond Jupiter
• Natural History Museum: Your dinosaur questions answered (2024) — around 50 dinosaurs named each year and why, where dinosaur fossils are found, and Triceratops’s size and frills