What is so unique about the precambrian era?

or:What is so unique about the precambrian era?or:Well that's the period when life began and when hard shelled creatures first appeared. Apart from t

or:What is so unique about the precambrian era?

or:Well that's the period when life began and when hard shelled creatures first appeared. Apart from that very little is known because most of the sedimentary rocks laid down in the period have undergone metamorphosis.

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