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Precambrian time
Earh forms; continental shields appear; fossils are rare; cyanobacteria are the most common organism. -
Period: to
L Haitof P.1
Geological Timescale -
Cambrian
Shelled marine invertebrates appear; trilobites and brachiopods are common; first vertebrates appear; atmosphere reaches modern O2-rich state. -
Ordovician
Echinoderms appear; brachiopods increase; trilobites decline; graptolites flourish. -
Silurian
Eurypterids, land plants and animals appear. -
Devonian
Age of fishes begins; amphibians appear; giant horsetails, ferns, and seed-bearing plants develop. -
Carboniferous / Mississippian Period
Amphibians flourish; brachiopods are common in oceans; forests and swamps cover most land. -
Carboniferous / Pennsylvanian Period
Giant cockroaches and dragonflies are common; coal deposits form; reptiles appear. -
Permian
Pangaea comes together; mass extinctions mark the end of the Paleolozoic Era. -
Triassic
Dinosaurs appear; ammonites are common; cyads and conifers are abundant; mammals appear. -
Jurassic
Dinosaurs are the dominant life-form; primitive birds and flying reptiles appear. -
Cretaceous
Flowering plants and modern birds appear; mass extinctions mark the end of the Mesozoic Era. -
Tertiary
Age of mammals begins; first primates appear. -
Quaternary
The last glacial ends; complex human societies develop.
