Dinosaur is the name given to prehistoric that lived on the earth for about 160 million years. Although dinosaurs were not lizards, the word dinosaur comes from the term Dinosauria, which means terrible lizards. Most dinosaurs were not very terrible either. These animals have been extinct for over 65 million years, but they have fascinated people for the last two centuries. .
Before the 1800's no one even knew that dinosaurs even existed. When people found a bone or tooth, they had no idea what it was. Around 1818, an English scholar, William Buckland, obtained a large lower jaw that contained a number of sharp teeth. After studying the jaw, he decided that it was unlike any other fossil ever found. He gave it the name Megalosarus, meaning great lizard. .
Around this time an English naturalist, Mary Ann Mantall, found a large tooth partly buried in a rock. She and her husband, Gideon, decided that the tooth looked like one of an iguana and thus named it Iguanodon. .
The Magalosarus and the Iguanodon were the first dinosaurs to actually have a name.
During the late 1800's and early 1900's, large deposits of dinosaur remains were discovered in North America, Europe, Asia, and Africa. During the late 1900's extensive research had begun on the fossils discovered, in order to determine how the animals may have looked, acted, lived, and became extinct. .
It has been determined that the dinosaurs lived during what is now called the Mesozoic Era. This era is divided into three periods: Triassic, Jurassic, and Cretaceous. The Triassic period lasted from approximately 248-213 million years ago, the Jurassic period lasted from about 213-145 million years ago, and the Cretaceous period from about 145-65 million years ago.
Scientist believe that the earth's continents were not always separated as they are today. About 250 million years ago, they formed a single land mass surrounded by an enormous sea.