Vol 9 Prehistoric Animals ... Introduction ... What is a prehistoric animal?
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Introduction

The story of the past

Life has existed on the Earth for billions of years.
Nature-Explorer.net is your Internet guide to the world of nature. Browse through the natural world from Rainforests to Deserts. Find out facts about animals from Komodo dragons to butterflies, from graceful dolphins to huge dinosaurs. All text and graphics are copyrighted by REMedia, or by third parties who are acknowledged within this web site.
When we look around us, we see a variety of different animal groups, from fish to birds, from tiny insects to huge mammals like the elephant and blue whale. These animals were not always on the Earth, however. When our planet was first born, it was too hot and inhospitable a place for any animal or plant to live. In the billions of years since the Earth cooled down, the climate and geology of our planet have stabilized, and the amazing variety of animals and plants that we see today have gradually evolved.

For more than 80 percent of Earth's history, our planet was inhabited by bacteria, single-celled animals and algae. The present complexity of life on our planet has only come about over the past 600 million years. Closely related animals or plants evolved in the same time frame. For example, the body plan of bony fish evolved during the Devonian period, and reptiles evolved later, during the Permian period. Although primitive mammals co-existed with the dinosaurs, the different mammal forms started to evolve rapidly after the dinosaurs died out 65 million years ago.