World's Largest Collection of Dinosaur Drawings and  Pictures

Dinosaurs were vertebrate animals that dominated the terrestrial ecosystem for over 160 million years, first appearing approximately 230 million years ago. At the end of the Cretaceous period 65 million years ago, dinosaurs suffered a catastrophic extinction, which ended their dominance on land. Modern birds are considered to be the direct descendants of theropod dinosaurs.

Since the first dinosaur was recognized in the 19th century, their mounted, fossilized skeletons have become major attractions at museums around the world. Dinosaurs have become a part of world culture and remain consistently popular, especially among children. They have been featured in best-selling books and blockbuster films such as Jurassic Park, and new discoveries are regularly covered by the media.

The superorder or clade "Dinosauria" was formally named by the English scientist Richard Owen in 1842. The term is a portmanteau derived from the Greek words δεινός (deinos - "terrible", "fearsome" or "formidable") and σαύρα (saura; "lizard" or "reptile"). Owen chose it to express his awe at the size and majesty of the extinct animals, not out of fear or trepidation at their size and often-formidable arsenal of teeth and claws. Dinosaurs were extremely varied. Some were herbivorous, others carnivorous. Some dinosaurs were bipeds, some were quadrupeds, and others — such as Ammosaurus and Iguanodon — could walk easily on two or four legs.

While the evidence is incomplete, it is clear that, as a group, dinosaurs were large. By dinosaur standards the sauropods were gigantic. For much of the dinosaur era, the smallest sauropods were larger than anything else in their habitat, and the largest were an order of magnitude more massive than anything else that has since walked the Earth.

All dinosaurs so far discovered share certain modifications to the ancestral archosaurian skeleton. Though some later groups of dinosaurs featured further modified versions of these traits, these shared derived features are considered typical across Dinosauria; the earliest dinosaurs had these features and passed them on to all their descendants. Such common structures across a taxonomic group are called synapomorphies. 230 million to 65 million years ago, reptiles called dinosaurs lived on the Earth. They varied tremendously in size and shape. Some were about the size of a dog but others were huge, weighing many tons. The largest species ate plants, but others were flesh eaters. Most were four-legged, but many walked and ran on their hind legs only. Dinosaur fossils have been discovered nearly worldwide, and major new finds are continually reported. These fossils include bones, eggs, footprints, and even traces of feathers. Based on their study of fossils, scientists have been able to classify dinosaurs into two main groups, the Saurischia ("lizard hips") and the Ornithischia ("bird hips"). Also using fossils as a guide, scientists have created life-size models that show how different events in a dinosaur's life may have occurred. But many mysteries remain. One of the biggest concerns the disappearance of the dinosaurs. Scientists have proposed various theories to account for the extinction of these fascinating animals, but none have been conclusively proven.

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