4 INTRODUCTION Dinosaurs roamed Earth for many millions of years The World of Dinosaurs Millions of years ago dinosaurs stomped dashed and glided around Earth Many grew to incredible sizes Others were very small Some hunted and ate meat Others grazed on plants All dinosaurs were reptiles Dinosaurs evolved and went extinct or died out during three time periods The first is the Triassic This period began 252 million years ago Back then Earth was much warmer than it is today The continents were one landmass It was
5 called Pangaea Pangaea The Jurassic Period was 201 million to 145 million years ago The Cretaceous came last The continents slowly separated during these time periods An asteroid hit Earth 66 million years ago This ended the Cretaceous Period Most dinosaurs went extinct But some survived They continued to evolve Birds are the living descendants of dinosaurs Sometimes dinosaur bones footprints eggs and other remains got preserved These are called fossils Scientists use fossils to learn more about dinosaurs Pterosaurs above and plesiosaurs below were not dinosaurs But they lived at the same time as dinosaurs
6 ALLOSAURUS ALLOSAURUS Range Allosaurus was a top predator during the Late Jurassic Period It is part of a group of meat-eating dinosaurs called theropods Allosaurus was very common in what is now North America Fossils that may be from Allosaurus have also been found in Portugal Tanzania Siberia and Australia Appearance Allosaurus could grow bigger than a school bus It looked like Tyrannosaurus But it was slightly smaller Allosaurus also had longer arms and small horns over its eyes It had sharp claws and long sharp teeth with serrated edges
Ferocious Predator Allosaurus could run very fast It ate plant-eaters including Camarasaurus and Stegosaurus Most likely it hunted alone It may also have been a scavenger This means it ate creatures that had recently died Triassic Period 252 million years ago When Did This Dinosaur Live Jurassic Period 201 million years ago Allosaurus fossil Length 39 to 43 feet 12 to 13 m 145 million years ago Weight 2.2 tons 2 metric tons Cretaceous Period 66 million years ago 7
