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Proterozoic

(prät′ə rə zō′ik, prōt′-)

adjective

designating or of the geologic eon characterized by the development of sedimentary rock, shallow seas, and the first soft-bodied, marine invertebrates; Precambrian, esp. late Precambrian

Origin: < Gr proteros, former, compar. of pro, forward (see pro-) + zo- + -ic

See Proterozoic in American Heritage Dictionary 4

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.

Origin:

Origin: Greek proteros, earlier, former; see per¹ in Indo-European roots

Origin: + -zoic

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