The Paleozoic ERA was a period of time that lasted from 541 million years ago to 251 million years ago. It is the first of three eras in the Phanerozoic Eon, and is divided into six periods: Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian. During this ERA, life on Earth diversified and many new species evolved, including the first fish, amphibians, reptiles, and land plants. The Paleozoic ERA is known for its great mountain-building events, which created the Appalachian Mountains in North America and the Ural Mountains in Russia.