ERA	Period	End Date (millions of years ago)	Notes
	None	580	Earth's history begins, first life forms in the sea; first prokaryotes appear, then the first eukaryotes appear.
Paleozoic	Cambrian Ordovician Silurian Devonian Carboniferous Permian	500 430 400 345 285 245	Age of invertebrates First fish appear ( jawless fish) Age of fish, first land plants appeared, first land arthropods First amphibians, insects developed. First reptiles, ice covered a large part of the earth, great coal forming forests. Major extinctions occurred, first cone bearing plants and ferns.
Mesozoic	Triassic Jurassic Cretaceous	195 135 65	Age of Reptiles. First dinosaurs, first mammals Rocky mountains rise, first birds, largest dinosaurs thrive. First flowering plants, dinosaurs die out, first placental mammals.
Cenozoic	Tertiary Quaternary	55 recent	Age of Mammals Primitive apes, ancient humans. Humans are the dominant organism.