Age of the dinosaurs

What is a dinosaur? 10

How do we know about them? 12

How long did dinosaurs rule? 14

Were all dinosaurs the same? 16

How was a dinosaur born? 18

Dinosaur Extinction

What is a dinosaur?

Dinosaurs were land-dwelling reptiles with long tails, clawed hands and feet, and scaly skin. Some walked on two legs, others on four. While some were meat-eaters, others munched on plants. Most people know what a dinosaur looks like from books and movies. But even experts are still unsure why dinosaurs survived when their rivals died out. It was probably their erect stance, the sheer size of the largest, such as Giganotosaurus, and their efficient weapons of attack and defense that ensured their long-lasting success.

In what way were dinosaurs different?

| A Dinosaurs were different from other reptiles because they could stand with their legs straight. Most reptiles have legs that splay out from their bodies, giving them a sprawling stance. Dinosaurs were like mammals—they could walk upright with their legs directly below them.

Long tail used for balance

Many dinosaurs had scaly skin covered with bumps

Semisprawling stance of a crocodile

Sprawling stance of a lizard

Was Eoraptor the first of the dinosaurs?

| A It was certainly one of the earliest dinosaurs. The remains of Eoraptor— a small, meat-eating dinosaur—were discovered in 1991 in South America, where dinosaurs may have originated. Experts estimate that Eoraptor was alive and well as long as 228 million years ago.

Erect stance of a Barosaurus

Barosaurus

Five-fingered hands with weaker claws than later species

Long tail used for balance

Many dinosaurs had scaly skin covered with bumps

Erect Stance

Erect stance of a Barosaurus

Barosaurus

Five-fingered hands with weaker claws than later species

Bones of Tyrannosaurus foot mSBSmfi^

Word Dinosaurs

The word dinosaur means "terrible lizard" and was first used in 1842.

Bones of Tyrannosaurus foot

Did dinosaurs have claws?

| A All dinosaurs had clawed feet and hands. Some claws were like the talons of birds of prey, while others resembled curved, sharp scissors. They were either used to hook high branches down for food or to slash live prey or stab at attackers. Some "claws" were more like the hooves of cattle and merely acted to protect the toes.

Chasmatosaurus

Chasmatosaurus

More Facts

The word dinosaur means "terrible lizard" and was first used in 1842.

■ Dinosaurs and pterosaurs evolved from a group of reptiles called archosaurs, which arose 250 million years ago.

■ Chasmatosaurus was one of the earliest archosaurs. It probably spent most of its time hunting fish in rivers, much like a modern crocodile.

Chasmatosaurus

Were there dinosaurs that could fly?

Dinosaurs were all land-dwelling animals. But there were plenty of flying creatures in the prehistoric skies, and they were reptiles, just like the dinosaurs. They were called pterosaurs, which means "winged lizard." There were many different types of pterosaur, some as big as light aircraft. Rhamphorhynchus was over 3 ft (1 m) long with a narrow jaw and pointed teeth for catching fish.

Were dinosaurs warm-blooded?

No one is sure. Reptiles such as snakes are cold-blooded, which means that their body temperature cools down with the outside temperature and they become less active. But evidence suggests that some dinosaurs, such as Velociraptor, had feathers, and feathered animals are warm-blooded. Some experts now believe that all the dinosaurs may have been warm-blooded, enabling them to be active whatever the weather.

Dinosaurs Warm Blooded Cold Blooded

How do we know about them?

Everything we know about dinosaurs comes from scientific evidence. That means the real, physical remains of the animals that have been preserved in the world's deserts, riverbeds, and cliffs for millions and millions of years. It was not until the 19th century that the remains were correctly identified and the science of paleontology was born. Since then, amazing discoveries have been made worldwide, including this complete skeleton of Coelophysis, unearthed in the sands of Texas.

Coelophysis Skeleton

What is a fossil?

A fossil is the preserved remains | A of a plant or animal. These remains can be either hardened bones, shells, or other parts, or a preserved impression of the hard parts. One of the most common fossils is an ammonite—a shelled sea creature that lived at the same time as the dinosaurs.

When were dinosaurs first identified?

| A People have been collecting dinosaur fossils for many years, but it was not until 1842 that dinosaurs were recognized as a distinct group of animals. When this jaw was found in England, experts realized that this, and other remains, belonged to extinct giant reptiles. Soon the term "dinosaur" was used to describe them.

Megalosaurus jaw

How is a fossil formed?

Fossils are formed by a process called mineralization. A creature dies and its soft parts rot away, leaving the skeleton. Minerals from water seep into the bones. The minerals eventually solidify, turning the bones into stone. Dinosaur fossils are often found in riverbeds, where the bodies have been quickly covered in sand and mud.

A dinosaur is chased into a slow-flowing river, where it drowns and

A dinosaur is chased into a slow-flowing river, where it drowns and

Dinosaur Bone Snacks

What is a paleontologist?

| A | Paleontologists are those scientists who study fossils. They work both at the world's fossil sites, excavating fossils, and in the laboratory, cleaning and analyzing fossils. Here, a paleontologist treats a sauropod bone before moving it from the Sahara Desert. Dinosaur bones are easily uncovered in the desert sands without the need to dig deep.

How is a fossil formed?

Fossils are formed by a process called mineralization. A creature dies and its soft parts rot away, leaving the skeleton. Minerals from water seep into the bones. The minerals eventually solidify, turning the bones into stone. Dinosaur fossils are often found in riverbeds, where the bodies have been quickly covered in sand and mud.

Fossils Minerial Seep

| A People often think that dinosaur skeletons in museums are real, but they are usually replicas. Paleontologists create a complete skeleton from synthetic bones, using a few fossilized bones and skeletons of dinosaur relatives as a guide. Some skeletons are made from a mix of fossilized and synthetic bones.

i q How do dinosaurs get their names?

| A Many dinosaurs are named after a distinguishing feature. For example, Triceratops means "three-horned face." Some are named because of where they were found—Argentinosaurus is a "reptile of Argentina." Others are called after the person who discovered them: Herrerasaurus means "Herrera's reptile."

How long did dinosaurs rule?

Dinosaurs stomped their way across the Earth for about 160 million years and were the dominant land animals for 143 million years. During this huge stretch of time (humans have been around for less than 2 million years), many species became extinct but others evolved to take their place. Dinosaurs were survivors and most were able to adapt to their ever-changing world. Dilophosaurus, although not the largest of dinosaurs, was a meat-eater from the Jurassic Period. The last dinosaur expired 65 million years ago.

Who ruled before the dinosaurs?

| A Before the age of the dinosaurs, the land was dominated by a group of animals that were neither reptiles nor mammals. The therapsids included this Lystrosaurus, a stocky, tusked plant-eater, about the size of a sheep. Most were extinct by 200 million years ago, when the dinosaurs grew dominant, although no one knows if they were wiped out by the dinosaurs.

Why Were Dinosaurs Die

Why do species die out?

A All Living things die, and all species eventually become extinct. Most individual species of dinosaur existed for about 2—3 million years. Some species evolved into different ones by adapting to changing habitats, while others were unable to adapt. Some, such as Plateosaurus, may have died out because of a violent change to the environment that wiped out many animals.

When did dinosaurs live?

Our planet Earth was probably formed about 4.5 billion years ago, and the first animal life appeared about 1 billion years ago. The age when dinosaurs lived (from 251—65 mya) is called the Mesozoic Era, and scientists divide this into three periods—Triassic, Jurassic, and Cretaceous.

Mesozoic Era Timeline

The first dinosaurs, such as Eoraptor and Herrerasaurus, appeared in the mid Triassic Period.

Dilophosaurus

The Jurassic Period was dominated by the giant plant-eaters. Plated dinosaurs, such as the stegosaurs, appeared then, too.

|251

Herrerasaurus

Lesothosaurus

Herrerasaurus

Lesothosaurus i years ago (mya) TRIASSIC

The Jurassic Period was dominated by the giant plant-eaters. Plated dinosaurs, such as the stegosaurs, appeared then, too.

The first dinosaurs, such as Eoraptor and Herrerasaurus, appeared in the mid Triassic Period.

Dilophosaurus

Dilophosaurus Fossil FoundTriassic Period Animals With Information

Lump on the vertebra, possibly caused by cancer

Mesozoic Era Dinosaurs

Model of Baryonyx

Lump on the vertebra, possibly caused by cancer

Did dinosaurs ever get sick?

| A Since the main dinosaur evidence is their bones, the only diseases that experts have found are those that affect the bones. This section of a dinosaur's backbone shows a tumor that may have been caused by cancer. Although it cannot be scientifically proved, it is likely that dinosaurs suffered from infectious diseases, just as animals do today.

How many groups existed together?

Many dinosaur species became extinct while new species evolved over the long period of dinosaur rule, so many species did not coexist. Even so, dozens or even hundreds of different species did live at the same time in the same area. Experts know that Velociraptor was around at the same time as Protoceratops, because fossilized bones of the two have been discovered locked in battle.

Dinosaur Alive Seismosaurus
Small head

Model of Baryonyx

How long did a dinosaur usually live?

| A Bigger animals usually have a longer lifespan than small ones, so it is likely that the big plant-eating dinosaurs lived the longest. If one of these had a lucky life, it may have survived for 200 years or more. However, most dinosaurs would have died from accidents, starvation, or illness long before they could reach old age.

3 The dinosaurs were at their height in the Cretaceous Period. Some grew horns and frills, others developed club tails, and some refined their killing instincts.

Triceratops

Triceratops

Europlocephalus

Europlocephalus Dinosauro
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Responses

  • Daniel
    How many years ago was the first dinosaur born?
    7 years ago
  • robel
    What species evolved into the first dinosaurs?
    7 years ago
  • ulrich
    What was the very first dinosaur alive called?
    7 years ago
  • Fiyori Yohannes
    What was the size of the eoraptor when it died?
    6 years ago
  • AARON
    How was dinosaurs born?
    6 years ago
  • ruthie
    Why did Dinuasors died?
    5 years ago
  • marmaduke
    Why was the Barosaurus tail is the least likely to get fossilized?
    4 years ago

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