The dawn of the Age of Dinosaurs, when all of Earth was just one giant continent.
When the Triassic period began more than 240 million years ago, the weather was warm and Earth had only one continent. Surrounding pools of water were ferns, cycads, and horsetails, and in the interior of the land, forests of ginkgos and conifer trees grew in desert-like conditions. This was the scene at the dawn of the Age of Dinosaurs. The first dinosaurs appeared late in the Triassic period, evolving from more primitive archosaurs, a group of reptiles that also gave rise to crocodiles and pterosaurs.
At the beginning of the Triassic period, all the continents were joined together into one "super-continent" called Pangaea. Without wide seas to block their path, dinosaurs and other prehistoric creatures could travel across the land. By the end of the Triassic period, Pangaea was breaking into two landmasses—Laurasia and Gondwanaland.
The dinosaurs were the last group of "ruling" reptiles to dominate the Earth. Here you can see representatives of other reptile groups that lived during the Permian period, which preceded the Age of Dinosaurs.
Plants preceded animals in adapting from life in the sea to life on land, and, like animals, plants have used a variety of methods to evolve under changing conditions. Prehistoric plants have been more successful than the dinosaurs—many primitive plant species still survive today.
Although large by current standards, the first dinosaurs were not the giants we see in movies and museums today. Small, primitive dinosaurs are being excavated and identified every year, especially in South America.
Source: Microsoft Dinosaurs (1993) CD-ROM. Text liberated from original screen art; images & audio restored from disc. Original media is Microsoft/supplier copyright — non-commercial educational preservation. Credits & Acknowledgements