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it is further subdivided into the Tonian, Cryogenian, and Ediacaran Periods. The most severe glaciation known in the geologic record occurred during the Cryogenian
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alot of multi-celled animals live in this time
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1,600 to 1,000 million years ago. The Mesoproterozoic was the first period of Earth's history of which a respectable geological record survives