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Georgia Perimeter College: The Permian Period
This resource provides basic information of the changes that took place during the Permian period as well as the animals that populated the Earth during this time.
University of California
Ucmp: Paleozoic Era: Stratigraphy
This site contains a chart showing the progression of the Paleozoic Era. Each section of the chart leads to information about the geological, biological, and climatic elements of a specific period of the era.