INTRODUCTION:- Millions of years ago, long before there were any people, there were Dinosaurs. Dinosaurs were one of several kinds of prehistoric reptile that lived during Mesozoic era “The age of reptiles.” Dinosaurs dominated the Earth for over 165 million years, but mysteriously went extinct 65 years ago. Palaeontologists study fossil remains to learn about the amazing world of dinosaurs. With the help fossils Palaeontologists can tell many Dinosaurs were tall, many were short, many were speedy, many were slow. NAMES OF FAMOUS DINOSAURS:- Camarasaurus Camarasaurus is far by one of the most numerous sauropods discovered and is one of the few dinosaurs we know what all the bones looked liked. It also held a small, but key role in the changing of the name Brontosaurus to Apatosaurus. T-rex T. rex was a huge meat-eating dinosaur that lived during the late Cretaceous period, about 85 million to 65 million years ago. T. rex lived in a humid, semi-tropical environment, in open forests with nearby rivers and in coastal forested swamps. Raptors Raptors came into their own during the late Cretaceous period (about 90 to 65 million years ago), but they roamed the earth for tens of millions of years before that. Ankylosaurs During the late Cretaceous period, Ankylosaurs reached the apex of their evolution. From 75 to 65 million years ago, some Ankylosaurs genera (most notably Ankylosaurs and Euoplocephalus) developed incredibly thick and elaborate armour, doubtless a result of the ecological pressures applied by bigger, stronger predators like Tyrannosaurus Rex. EXTINCTION:- There are many reasons of Dinosaurs extinction some of them are: A big meteorite crashed into Earth, changing the climatic conditions so dramatically that dinosaurs could not survive. Ash and gas spewing from volcanoes suffocated many of the dinosaurs. Diseases wiped out entire populations of dinosaurs. Food chain imbalances lead to the starvation of the dinosaurs.