EON	ERA	PERIOD		EPOCH	TIME SPAN (million years)	AGE of
Phanerozoic	Cenozoic	Quaternary		Holocene	0-2	Mammals	Humans
				Pleistocene			Mammals develop and become dominant Extinction of dinosaurs (beginning of Paleocene)
		Tertiary	Neogene	Pliocene	2-5
				Miocene	5-24
			Paleogene	Oligocene	24-37
				Eocene	37-58
				Paleocene	58-66
	Mesozoic	Cretaceous			66-144	Reptiles	Flowering plants, height of dinosaurs
		Jurassic			144-208		1st birds/mammals, abundant dinosaurs
		Triassic			208-245		First Dinosaurs
	Paleozoic	Permian			245-286	Amphibians	End of trilobites & other marine animals
		Carbon- iferous	Pennsylvanian		286-320		Abundant insects, first reptiles
			Mississippian		320-360		Large primitive trees
		Devonian			360-408	Fishes	First amphibians
		Silurian			408-438		First land plant fossils
		Ordovician			438-505	Marine Invertebrates	First Fish
		Cambrian			505-570		1st shelled organisms, trilobites dominant
Proterzoic	Also known as Precambrian				570-2,500		First Multicelled organisms
Archean					2,500-3,800		First one-celled organisms
Hadean					3,800-4,600		Approx age of oldest rocks (3800)