All About Dinosaurs

A World Before People

Imagine a world with no cities, no cars and no people. The land is covered in giant ferns and tall trees. Strange calls echo through the forest. Huge creatures stomp across the ground, and the earth shakes beneath their feet. This was the world of the dinosaurs.

Dinosaurs were a group of reptiles that lived on Earth for a very, very long time — more than 150 million years. They lived and died out long before the first humans were born. In fact, no person ever saw a living dinosaur.

So how do we know they were even here? The answer is hidden in the rocks. In this book you will discover how scientists learn about dinosaurs, meet some of the most amazing kinds, find out what they ate and how they lived, and solve the great mystery of why they disappeared. Let's travel back in time.

What Is a Dinosaur?

A dinosaur was a kind of reptile, like lizards and crocodiles are today. Most reptiles have scaly skin and lay eggs, and dinosaurs were the same. But dinosaurs were special in one important way: their legs grew straight down underneath their bodies, instead of sticking out at the sides like a lizard's. This let them stand tall and walk or run well, holding their bodies high off the ground.

Dinosaurs came in an incredible range of shapes and sizes. Some were as tiny as a chicken. Others were the biggest animals ever to walk on land, longer than a school bus and taller than a house. Some walked on four legs, and some ran on just two. Some had horns, spikes, plates or thick armour to protect themselves.

The word "dinosaur" means "terrible lizard", a name given by scientists long ago. But not all dinosaurs were terrible at all. Many were gentle giants that spent their days munching plants.

How Do We Know? Fossils!

We know about dinosaurs because of fossils. A fossil is the remains or trace of a living thing from long ago that has slowly turned to stone.

Here is how a fossil forms. When a dinosaur died, its body might be quickly covered by mud or sand. Over thousands and thousands of years, the soft parts rotted away, but the hard parts — like bones and teeth — stayed. Slowly, minerals seeped into them and turned them as hard as rock. Layer upon layer of mud built up on top, squashing down into stone. The bones became a fossil locked inside the rock.

Not all fossils are bones. Sometimes we find fossil footprints, where a dinosaur stepped in soft mud that later hardened. We even find fossil eggs and fossil dung! Each one is a clue about how dinosaurs lived.

Scientists who dig up and study fossils are called palaeontologists. They search in rocky places all over the world. When they find fossils, they dig them out very carefully with small tools and brushes so the precious bones are not broken. Then they piece the bones together, like a giant jigsaw puzzle, to work out what the dinosaur looked like.

The Plant-Eaters

Many dinosaurs ate only plants. An animal that eats only plants is called a herbivore. There were no flowers or grass in the earliest dinosaur days, so they fed on ferns, leaves and the branches of trees.

The biggest plant-eaters of all belonged to a group called the sauropods. These were the gentle giants with long, long necks, long tails and round bodies on four sturdy legs. Brachiosaurus was one of these. Its neck was so long it could reach the leaves at the tops of tall trees, like a giant living crane. To grow so big, sauropods had to eat enormous amounts of plants all day long.

Other plant-eaters protected themselves with amazing body armour. Triceratops had three sharp horns on its face and a wide bony frill around its neck, a bit like a shield. Stegosaurus had rows of big bony plates along its back and four dangerous spikes on its tail to swing at enemies. Ankylosaurus was covered in thick armour and had a heavy club of bone at the end of its tail, which it could swing like a giant hammer.

The Meat-Eaters

Other dinosaurs were hunters that ate meat. An animal that eats meat is called a carnivore. Meat-eating dinosaurs usually had sharp claws, powerful legs for running, and mouths full of sharp, pointed teeth for grabbing and tearing.

The most famous meat-eater of all is Tyrannosaurus rex, often shortened to T. rex. It was one of the largest meat-eaters ever, with a huge head and teeth as long as bananas. Its bite was one of the strongest of any animal that has ever lived. Yet its little front arms were surprisingly small and weak.

Not all hunters were huge. Velociraptor was much smaller, about the size of a large turkey, but it was fast and clever. It hunted using a large, curved claw on each foot. Scientists now believe Velociraptor and many other small meat-eaters were covered in feathers, a bit like birds.

Meat-eaters and plant-eaters lived side by side. The plant-eaters' horns, armour and spikes helped protect them from being caught by the hungry hunters.

How Dinosaurs Lived

Dinosaurs did far more than just eat and fight. They lived full lives, much as animals do today.

Like other reptiles, dinosaurs laid eggs. Palaeontologists have found fossil nests with eggs still inside, and even fossils of baby dinosaurs. Some dinosaurs may have looked after their young and brought them food, just as birds care for their chicks.

Many dinosaurs lived together in groups called herds. We know this because fossil footprints show many dinosaurs of the same kind walking together in the same direction. Living in a herd helped keep the plant-eaters safe, because there were more eyes to watch for danger.

Dinosaurs lived all over the world, in hot deserts, green forests and swampy marshes. They ruled the land for so long that whole new kinds appeared and disappeared while others carried on.

The Great Mystery

If dinosaurs were so successful for so long, what happened to them? About 66 million years ago, almost all the dinosaurs suddenly disappeared. This is one of the biggest mysteries in science, but palaeontologists think they have found the answer.

Most scientists believe that a giant rock from space — an asteroid — crashed into the Earth. The crash was so enormous that it threw huge clouds of dust into the sky, blocking out the sunlight for a long time. Without enough sunlight, plants struggled to grow. The plant-eaters could not find enough food, and then the meat-eaters had nothing to hunt. One by one, the great dinosaurs died out.

It was a sad ending for these amazing animals. But the story does not stop there.

Dinosaurs Today

Here is a wonderful surprise: dinosaurs are not entirely gone! When the big dinosaurs died out, one small group survived. That group slowly changed over millions of years into the birds we see today.

That's right — the sparrow in your garden, the duck on the pond and the chicken on a farm are all distant cousins of the dinosaurs. Birds are the dinosaurs' closest living relatives. The next time you watch a bird hop across the grass, you are looking at a tiny, feathered reminder of the age of dinosaurs.

What We Learned

We have travelled back in time over 66 million years and met some astonishing creatures!

We learned that dinosaurs were reptiles that ruled the Earth long before people existed. We know about them thanks to fossils, dug up and studied by palaeontologists. Some dinosaurs were plant-eating herbivores, like the long-necked Brachiosaurus and the armoured Triceratops. Others were meat-eating carnivores, like the mighty T. rex. Most dinosaurs died out after an asteroid struck the Earth, but birds carry on their family line to this day.

The world of the dinosaurs is gone, but every new fossil helps us picture it a little more clearly.

Hungry for more true adventures from long ago and far away? Take a trip through space in The Solar System: A Young Reader's Guide, or dive into the dark depths with Explorers of the Deep Sea.