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Proterozoic

Proterozoic The eon of geological time extending from the end of the Archaean, about 2600 million years ago, to the start of the present eon (see Phanerozoic), about 570 million years ago. Life in the early Proterozoic was dominated by bacteria, which flourished in shallow seas and muds. They depended on a wide variety of metabolic strategies, including photosynthesis, which were crucial in determining the composition of the earth's atmosphere and oceans. The oldest eukaryotic fossils date from after the middle Proterozoic, about 1200 million years ago. These early protoctists are thought to have arisen through symbiotic associations of various prokaryotes (see endosymbiont theory), probably on several independent occasions. Towards the end of this eon comes the first fossil evidence of multicellular animal life, the so-called Ediacara fauna, named after a rocky outcrop in Australia but also found elsewhere. These rocks, dated to around 650 million years ago, reveal traces of soft-bodied fanlike or quiltlike creatures, perhaps unrelated to any modern forms, as well as animals resembling jellyfish and worms.

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Proterozoic

Proterozoic The eon of geologic time, 2500–542 Ma ago, between the Archaean and Phanerozoic Eons, and ending in the abundantly fossiliferous Ediacaran Period. It wa the final period of the former Precambrian

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Proterozoic

Proterozoic The most recent of the three subdivisions of the Precambrian, dated at about 2500–590 Ma ago. It culminated with the first abundantly fossiliferous period, the Ediacaran.

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Proterozoic

Proterozoic The most recent of the three subdivisions of the Precambrian, dated at about 2500–590 Ma ago.

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Proterozoic

Proterozoic The most recent (about 2500–575 Ma ago) of the three subdivisions of the Precambrian.

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