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Proterozoic

Definition of Proterozoic

adjective

Geology

relating to or denoting the aeon that constitutes the later part of the Precambrian, between the Archaean aeon and the Cambrian period, in which the earliest forms of life evolved.
(as noun the Proterozoic) the Proterozoic aeon or the system of rocks deposited during it.

The Proterozoic lasted from about 2,500 to 570 million years ago. For millions of years only bacteria and single-celled organisms existed, and the early invertebrates that followed were soft-bodied and rarely left any trace in the form of fossils

Origin:

late 19th century: from Greek proteros 'former' + zōē 'life', zōos 'living' + -ic

Proterozoic in other Oxford dictionaries

Definition of Proterozoic in the US English dictionary

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