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GEOLOGIC TIME TABLE THE LAST 4600 MILLION YEARS
Millions of years ago	ERA	PERIOD	EVENTS
4600	Precambrian	Precambrian	The formation of the Earth's crust and the subsequent evolution of life
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4550 +	Precambrian era lasts from 4600 million years ago to 570 million years ago, a span of over four billion years. A straight-line time- axis showing this would extend about 400 lines here
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600 +
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|	Palaeozoic	Cambrian	Marine animals with mineralized shells appear: trilobites, echinoderms, brachio-pods, molluscs, primitive graptolites; a variety of worms
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550 +
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500 +		Ordovician	Graptolites dominant; also trilobites, brachiopods, bryozoans, gastropods, bivalves, echinoids, crinoids, cephalopods, and corals
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450 +
|		Silurian	Barchiopods, crinoids, corals, corals; primitive fish
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400 +		Devonian (395)	Corals, brachiopods, ammonoids, crinoids; fishes and early land plants
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350 +		Carboniferous (345)	Foraminiferans, corals, bryozoans, brachiopods, blastoids; seed ferns, lycopsids, and other plants; amphibians become more common
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300 +
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|		Permian	Trilobites extinct; Amphibians and reptiles dominant land animals; gymnosperms dominant plants Molluscs dominant
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250 +
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|	Mesozoic	Triassic	invertebrates; reptiles dominant: turtles, dinosaurs, ichthyosaurs
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200 +
|		Jurassic	Ferns, cycads, ginkgos, rushes, conifers; ammonites and other invertebrates; pterosaurs, Archaeopteryx appears
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150 +
|	Cretaceous (136)		Angiosperm plants; Mesozoic reptiles peak
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100 +
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|	Cenozoic	Tertiary (65)	Mass extinction: dinosaurs, pterosaurs, and ammonites extinct; rise of modern animals; shrubs, grasses, and other flowering plants
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50 +		.
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PRESENT +		Quaternary (1.8)