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Geologic Time Scale - Pre-Mesozoic

(250 million years ago to approximately 4.6 billion years ago)
ERA PERIOD EPOCH DATES AGE of Events
Cenozoic  
Mesozoic  
Paleozoic Permian 250-286 Amphibians End of trilobites
Carboniferous Pennsylvanian 286-320 First reptiles
Mississippian 320-360 Large primitive trees
Devonian 360-408 Fishes First amphibians
Silurian 408-438 First land plant fossils
Ordovician 438-505 Invertebrates First Fish
Cambrian 505-570 1st shells, trilobites dominant
Also known as Precambrian 570-2,500 1st Multi-celled organisms
2,500-3,800 1st one-celled organisms
3,800-4,600 Approx. age of oldest rocks 3,800

Note: Dates are in millions of years

Modified from University of Alaska-Fairbanks, Geoscience Web SiteTaken from: MODERN PHYSICAL GEOLOGY,
Graham R. Thompson Ph.D., Jonathan Turk Ph.D., Saunders College Publishing.

 

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