Dinosaurs—their name means “terrible lizards”—were the most successful land animals that ever lived. They came in all sorts of shapes and sizes and dominated the world for more than 150 million years. Modern man has been around for only 400,000 years. The last dinosaurs died out 65 million years ago. The combined effects of a meteorite impact and volcanic activity probably caused their extinction. One group survived and is all around us today. They are the birds.





WHAT WERE DINOSAURS?

Dinosaurs lived on the land. They did not live in the sea and they did not fly. They were reptiles—animals with a backbone, four legs and scaly skin. Most reptiles lay eggs with a waterproof shell; dinosaurs did that too. Dinosaurs had one special feature that made them different from all other reptiles—they had straight legs. Reptiles’ legs stick out sideways from their bodies. They have to use a lot of energy when they move because their bodies drag along the ground and they have to twist from side to side to walk. Their elbow and knee joints have to move their legs sideways and their hands and feet forwards. You cannot run very fast or very far with such a clumsy system. Dinosaurs tucked their legs underneath their bodies. That supported their body weight and made walking and running much easier. Dinosaur footprints show that they walked with one foot in front of the other just like four-legged mammals or two-legged human beings. This was what made dinosaurs so successful

WHEN AND WHERE DID THEY LIVE?
The oldest known dinosaurs lived about 228 million years ago during the Triassic Period. They lived through the Jurassic Period and the last ones died out 65 million years ago at the end of the Cretaceous Period. Tyrannosaurus and Triceratops were two of the very last dinosaurs. Dinosaurs lived all over the Earth on every continent. Several kinds have even been found in Antarctica. Antarctica is very cold and covered in ice today. When dinosaurs were alive it was quite warm and covered in forests. Their world was very different from ours. The continents were all joined together 200 million years ago and dinosaurs could wander everywhere. Later in the age of dinosaurs, the continents began to split apart. This meant that newly evolving dinosaurs were restricted to certain land areas by ocean barriers. That is why Tyrannosaurus and Triceratops lived only in western North America.

DIFFERENT KINDS OF DINOSAUR More than 900 different kinds of dinosaurs have been found. We divide them into two groups called Saurischia and Ornithischia based on the shape of their hips. The saurischians include all the meat-eaters. They are called theropods. Theropods walked on two legs and had sharp curved claws on their fingers. The sauropods (plant-eaters) are saurischians too, because they had the same shaped hips. The ornithischians include armoured dinosaurs (ankylosaurs); plated dinosaurs;(stegosaurs); dinosaurs with dome-shaped heads (pachycephalosaurs); ornithopods, which included duck-billed dinosaurs (hadrosaurs); and horned dinosaurs (ceratopians).