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Cambrian Period. 570-500 MYA
All life marine. Trilobites abundant -
Ordovician. 500-435 MYA
Earliest fishes. Invertebrates, coelenterates, and mollusks are abundant. Echinoderms begin to have variants. -
Silurian. 435-395 MYA
Earliest terrestial plants and animals. Peak development of euryplerids. -
Devonian. 395-345 MYA
Earliest amphibians and ammonites. Mass extinction of armored fishes. unarmored fish become abundant. -
Carboniferous. 345-280 MYA
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Permian. 280-225 MYA
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Triassic. 225-195 MYA
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Jurassic. 195-136 MYA
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Cretaceous. 136-65 MYA
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Tertiary. 65-1.8 MYA
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Quarternary. 1.8 MYA-Present