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Tonian Period
1000–720 million years ago
Rodinia reconstruction.jpg

The Tonian (from Greek tonas, "stretch") is the first geologic period in the Neoproterozoic Era and lasted from 1000 Mya to ~720 Mya (million years ago). Instead of being based on stratigraphy, these dates are defined by the ICS based on radiometric chronometry.

Events leading to the formation of supercontinent Rodinia started in this period[contradicts Rodinia and Stenian wiki pages, help clarify?].

The first radiation of acritarchs occurred during the Tonian.