A brief prehistory of time:

15Bya - Universe Forms
4.6Bya - Solar system forms
4.5Bya - Earth's crust forms


3800MY: oldest rocks
800MY : 1st red algae
700 MY: 1st animals
500 MY: 1st land plants
350 MY: 1st reptiles
200 MY: 1st dinosaurs


Precambrian Era, 4550 - 550MY
Paleozoic Era (570MY-251MY)
Periods in Paleozoic:
 Cambrian, 550-505MY - first jawless fishes
 Ordovician, 505-438MY - more jawless fishes
 Silurian, 438-408MY - 1st ray finned/lobed fish
 Devonian, 408-360MY - fish dominant, 1st amphibians
 Carboniferous, 360-286MY - amphibians and fish
    - Mississippian period, 360-322MY
    - Pennsylvanian period, 322-286MY
 Permian 286-248MY - amphibians dominant, 1st mammal-like reptiles, pangaea forms

Extinction Event 251MY - all trilobites extinct

Mesozoic Era (251MY-65MY) - "Age of reptiles"
Periods in Mesozoic:
 Triassic, 251-225MY - reptiles, 1st dinosaurs
 Jurassic, 213-144MY - dinosaurs dominant, first mammals, birds
 Cretaceous, 144-65MY - dinosaurs dominant, small mammals, birds, T. Rex 75MY

Extinction Event 65MY - K-T extinction kills dinosaurs

Cenozoic Era (65MY-present) - "Age of mammals"
Periods in Cenozoic:
  Tertiary, 65-2MY
  Epochs in Tertiary:
    Paleocene, 65-54MY
    Eocene, 54-38MY
    Oligocene, 38-26MY
    Miocene, 26-7MY
    Pliocene, 7-2MY
 Quaternary, 2MY-present
  Epochs in Quaternary:
    Pleistocene, 2MY-10000Y
    Holocene, 10000Y-present

Extinction Event - Current day