GEOLOGIC TIME SCALE

eraperiodepochfeaturesbegan years before
the present (bp)
CenozoicQuaternaryHolocene (Recent)modern humans10,000
PleistoceneEarly humans, glaciation2,000,000
TertiaryPliocenemammals5,000,000
Miocene24,000,000
Oligocene37,000,000
Eocene55,000,000
Paleocene65,000,000
MesozoicCretaceous
reptiles140,000,000
Jurassicdinosaurs200,000,000
Triassicreptiles, early dinosaurs225,000,000
PaleozoicPermianamphibians280,000,000
Pennsylvanian320,000,000
Mississippian350,000,000
Devonianfishes400,000,000
Silurian
430,000,000
Ordovicianmarine invertebrates500,000,000
Cambriantrilobites570,000,000
Precambrian
abundant fossils
through
formation of earth
4,600,000,000

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