Dinosaurs

Dinosaurs were amazing reptiles that lived on Earth a very, very long time ago, long before people. Some were bigger than a bus and some were as small as a chicken. They walked the land for millions of years, and then died out ages before the first humans appeared.

Dinosaurs came in every size you can imagine. The biggest, the long-necked giants, were taller than a house and longer than a swimming pool. The smallest were about the size of a chicken or a house cat. So not all dinosaurs were huge, some were tiny.

Some dinosaurs ate only plants, munching leaves, ferns and treetops all day long. Others were meat eaters that hunted or scavenged other animals. You can often tell them apart by their teeth: flat teeth for grinding plants, and sharp, pointed teeth for tearing meat.

Nobody has ever heard a dinosaur, so we cannot be sure. But by studying their bones and their closest living relatives, birds and crocodiles, scientists think many dinosaurs boomed, honked, hissed or rumbled rather than roaring like a lion in films. Some may have made deep sounds we would feel more than hear.

Tyrannosaurus rex, or T. rex, was one of the biggest meat-eating dinosaurs, with a huge head and teeth as long as bananas. It walked on two strong back legs and had surprisingly tiny arms. It was a fierce hunter, but its little arms were still strong enough to grip.

The giant long-necked dinosaurs used their necks to reach food that other animals could not. Stretching up high, they could munch leaves from the very tops of tall trees, a bit like a giraffe today. A long neck also let them sweep across lots of low plants without moving their heavy bodies.

Triceratops was a plant eater with three sharp horns and a big bony frill around its neck. It probably used its horns to defend itself from hungry hunters and maybe to show off to other Triceratops. The wide frill may have protected its neck or made it look bigger and scarier.

Stegosaurus was a plant eater with a row of large, flat plates running down its back and sharp spikes on its tail. The plates may have helped it warm up or cool down in the sun, or made it look bigger to enemies. The spiky tail was a powerful weapon for swinging at attackers.

Yes, all dinosaurs hatched from eggs, just like birds and many reptiles do today. They laid their eggs in nests on the ground, sometimes in careful circles or mounds. Scientists have found fossil dinosaur eggs, and a few even have tiny baby dinosaur bones still curled up inside.

Baby dinosaurs hatched out small and often had to grow very fast to become huge adults. A giant long-neck could start smaller than a football and grow into the largest animal on land. Scientists can even count faint growth rings inside dinosaur bones, a bit like the rings in a tree.

Some dinosaurs did seem to care for their young. Scientists have found nests grouped close together, and one dinosaur was even named "good mother lizard" because its nests suggested it looked after its babies. Living in herds may also have helped keep the little ones safe.

Some dinosaurs were speedy and some were slow, depending on their bodies. Small, light meat eaters with long legs could dash quickly, maybe as fast as a car in town. The giant long-necks were far too heavy to run and simply plodded along on their huge legs.

Dinosaurs lived a very long time ago, so long that it is hard to imagine. They first appeared over two hundred million years before us, and they ruled the land for an incredibly long time. The last of them died out about sixty-six million years ago, ages before the very first people.

Dinosaurs shared their world with many other creatures. Giant reptiles with wings flew through the sky, and huge reptiles with flippers swam in the seas, though neither were true dinosaurs. There were also insects, small furry mammals and plants everywhere, all living alongside the dinosaurs.

Yes, quite a few dinosaurs had feathers, especially smaller meat eaters. Some feathers were fluffy for keeping warm, and others were colourful for showing off, long before any dinosaur could fly. These feathery dinosaurs are a big clue that birds today are their living relatives.

Long, long ago, something changed the whole world very fast, and most dinosaurs could not survive it. They died out about sixty-six million years ago, along with many other creatures. But not every dinosaur vanished, because the birds you see today are their living cousins.

When a dinosaur died and was quickly buried in mud or sand, its soft parts rotted away but its hard bones stayed protected. Over millions of years, water carrying minerals slowly seeped in and turned those bones to stone. What we dig up today is a rocky copy of the original dinosaur bone.

Fossil hunters search rocky places where old layers of the Earth are exposed, looking for bits of bone poking out. When they find one, they dig very carefully with small tools and brushes so they do not break anything. Then they wrap the fossils in protective jackets to carry them safely to a museum.

For a long time nobody knew dinosaur colours, so they were only a guess. But in some beautifully preserved feathered fossils, scientists found tiny structures that once held colour. By comparing them with the same structures in modern birds, they can now work out real colours and patterns for a few dinosaurs.

Fossil bones are almost never found complete, so scientists work like puzzle solvers. They clean each bone, figure out where it fits, and compare it with other, more complete dinosaurs to fill in missing pieces. Then they mount the bones on a strong frame so the whole dinosaur can stand up in a museum.

A dinosaur's teeth are one of the best clues to its meals. Flat, blunt teeth were good for grinding tough plants, while sharp, blade-like teeth were made for slicing meat. Scientists also study fossil dung and even stomach contents to find out exactly what was on the menu.

Dinosaur tails did many important jobs. Long, heavy tails helped the big two-legged dinosaurs balance as they walked and ran. Some dinosaurs had tails with clubs or spikes to swing at attackers, while the giant long-necks may have cracked their whip-like tails to make a loud warning.

The biggest dinosaurs were built like living cranes and bridges. Their legs were thick, straight pillars, perfect for holding up tons of weight. Surprisingly, many had hollow, air-filled bones that made them lighter than they looked, so they could grow enormous without collapsing.

Plant-eating dinosaurs could not fight like hunters, so many grew amazing armour instead. Some were covered in bony plates and studs like a living tank, and a few had heavy clubs on the ends of their tails. Others relied on sharp horns, thick frills, or simply staying together in a herd.

The flying reptiles of the dinosaur age, called pterosaurs, were close cousins of dinosaurs but not dinosaurs themselves. They ruled the skies on wings made of skin stretched between their bodies and a very long finger. Some were as small as a bird, while the biggest had wings wider than a small plane.

While dinosaurs ruled the land, huge reptiles ruled the ancient oceans. Some looked like dolphins with long snouts, others had long necks and paddle-shaped flippers, and a few were fierce hunters bigger than a bus. Like dinosaurs, these sea reptiles were not fish and had to come up to breathe air.

The biggest flying animals of all time were the largest pterosaurs, giant reptiles from the dinosaur age. The very biggest had wings as wide as a small aeroplane, yet light hollow bones helped them take to the sky. Standing on the ground, one could look a giraffe in the eye.

Pterosaurs flew on wings made of a tough, stretchy skin held out by one enormously long finger. Their bones were hollow and light, which made lifting off easier, and their strong shoulders and chest powered each flap. Many were superb gliders, riding the wind for long distances with barely a beat.

Yes. Scientists now agree that birds are a kind of dinosaur that never died out. They descended from small, feathered, meat-eating dinosaurs and carry many of the same features, like hollow bones and wishbones. So the sparrow in your garden is a real dinosaur, just a small and feathery one.

Feathers did not start out for flying at all. The first feathers were simple and fuzzy, and they most likely helped dinosaurs stay warm or show off bright colours to each other. Only much later did some feathers grow long and stiff enough to help their owners glide and finally fly.

Archaeopteryx was an amazing creature, about the size of a crow, that was half dinosaur and half bird. It had feathers and wings like a bird, but also teeth, clawed hands and a long bony tail like a dinosaur. It is one of the best clues we have that birds slowly evolved from dinosaurs.

Almost all dinosaurs died out long ago, but one group made it through: the ancestors of today's birds. These small, feathered dinosaurs survived the disaster that wiped out the giants, and over millions of years their descendants became every bird alive today. So dinosaurs are still all around us.

About sixty-six million years ago, a huge space rock crashed into the Earth with unbelievable force. It threw so much dust into the sky that sunlight was blocked for a long time, plants died, and the food chain collapsed. Along with huge volcano eruptions around the same time, this wiped out most dinosaurs.

The object that struck Earth was a huge asteroid, a rocky chunk left over from the birth of the solar system, likely more than ten kilometres across. It slammed into what is now the Gulf of Mexico at enormous speed. The impact released more energy than millions of the biggest explosions people have ever made.

Scientists found a thin layer of special dust in rocks all around the world, right at the moment the dinosaurs vanished. This dust is rich in a metal that is rare on Earth but common in asteroids. Later they even found the giant buried crater, which matched the same age, confirming the story.

When the giants died out, many small animals pulled through, including the ancestors of birds, along with mammals, insects, crocodiles and turtles. Being small often helped, because tiny creatures needed less food and could hide or shelter. When sunlight returned, these survivors spread out and filled the empty world.

Dinosaurs ruled the land for an astonishing amount of time, more than one hundred and fifty million years. That is so long that the famous T. rex actually lived closer in time to us than to the earliest dinosaurs. Humans have been around for only a tiny sliver of that vast history.

The long age of dinosaurs is split into three parts. In the first, dinosaurs first appeared and were mostly small. In the second, giant long-necks and many others grew huge. In the third and last, famous dinosaurs like T. rex and Triceratops lived, right up until the great extinction ended their reign.

Scientists work out a fossil's age mostly from the rock layers around it. Layers pile up over time, so deeper usually means older, like pages stacked in a book. They also measure special clocks hidden in certain rocks, natural materials that change at a steady, known rate, to pin down an age in millions of years.

When dinosaurs first appeared, all the land was joined in one giant supercontinent, so early dinosaurs could roam almost everywhere. Over millions of years the land slowly split apart and drifted into separate continents. Groups of dinosaurs were carried away from each other and evolved into different kinds in different places.

Modern scanning machines let scientists peek inside a fossil without breaking it open. By making detailed pictures of the inside of a skull, they can study the shape of a dinosaur's brain and its senses. Cutting thin slices of bone under a microscope even reveals growth rings, showing how fast the animal grew.

Scientists work out dinosaur speeds without ever seeing one move. They measure fossil footprints, because the gap between steps hints at how fast the animal was going. They also use the size and shape of the legs, plus computer models, to estimate whether a dinosaur sprinted, jogged or merely plodded.

Bringing dinosaurs back like in the movies is not possible, at least not for real dinosaurs. To copy an animal you need its DNA, but DNA slowly falls apart and none can survive the tens of millions of years since dinosaurs died. Scientists study their fossils and their living bird relatives instead.

Yes, and more often than ever before. Fossil hunters around the world find new kinds of dinosaurs almost every week, often on average close to one a week. Each new discovery adds another piece to the picture, and there are surely many more still buried, waiting to be found.

Dinosaurs did not appear out of nowhere. They evolved from earlier reptiles that lived before them, slowly changing over millions of years. Early dinosaurs were small and walked on two legs, and only later did some branches grow into giants, armoured tanks and long-necked titans.

Over their vast reign, dinosaurs had a huge amount of time to change and spread into every corner of the land. Different groups adapted to different lives: some to eating high leaves, some to hunting, some to armour or speed. Filling so many different roles led to an incredible variety of dinosaurs.

Birds evolved from a group of small, feathered, meat-eating dinosaurs over millions of years. Little by little, their arms turned into wings, their bones grew lighter and hollow, and their feathers became better for gliding and then for flapping. Step by tiny step, ground-running dinosaurs became the birds of today.

Dinosaurs show us that life on Earth is always changing, over spans of time far longer than we can easily imagine. They ruled for ages, then a sudden disaster reshaped the whole living world, yet life carried on in new forms. Their story reminds us how amazing, tough and surprising life can be.