Definition of Proterozoic

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< proteose

protest >

Prot·er·o·zo·ic

(pr

-z

k, pr

r-) KEY

ADJECTIVE:

Of or relating to the later of the two divisions of Precambrian time, from approximately 2.5 billion to 570 million years ago, marked by the buildup of oxygen and the appearance of the first multicellular eukaryotic life forms. See Table at geologic time.

NOUN:

The Proterozoic Eon.

ETYMOLOGY:
Greek proteros, earlier, former; see per¹ in Indo-European roots + -zoic

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