Geologic Time Scale

(Periods are noted for the beginning of each time interval as "MYA" meaning millions of years ago )

Era Period/MYA Age of  
Cenozoic Era

Quarternary
1.8 to Present

Mammals Early man appears. Northern glaciation. Modern man spreads worldwide; Many mammals vanish
Tertiary
65
Modern types of flowering plants appear. Spread and diversification of mammals. First placental mammals. Extinction of dinosaurs.
Mesozoic Era
Cretaceous
146
Reptiles Dinosaurs and many other organisms become extinct. Flowering plants appear.
Jurassic
203
First birds and mammals. Dinosaurs increasingly abundant.
Triassic
251

Break up of Pangea. First dinosaurs. Abundant cycads and conifers

Paleozoic Era Permian
295
Amphibians End of trilobites. Extinction of many marine animals.
Carboniferous
362
Age of Amphibians. First reptiles; Great coal forests; First conifers;
First cycads
Devonian
418
Fishes First amphibians and insects; Fishes abundant
Silurian
439
First land life (plants and invertebrates)
Ordovician
490
Invertebrates First fish.
Cambrian
543
First shells, marine life including trilobites
Precambrian All time before Paleozic. First living things perhaps 3.6 billion years ago .

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