420 Mya to 300 Mya Mya means million years ago.
419.2 Mya to ca 360 Mya, Earth: The Devonian period of the the Paleozoic era. This period has been divided to early, middle, and late parts. the late part ending in a mass extinction event.
251.9 Mya to 201.3, Triassic:This is the first geological of the Mesozoic Era. The Triassic falls between the Permian and Jurassic Periods. At this time a first evidence of mammals was seen, a mouse size critter. This geologic period ended with a mass extinction of species.
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