GEOLOGIC TIME
EONERAPERIODS AND
SYSTEMS
EPOCHS AND
SERIES
BEGINNING OF
INTERVAL*
BIOLOGICAL FORMS
PhanerozoicCenozoic Quaternary Holocene

Pleistocene
0.01

1.6


Earliest humans
TertiaryPliocene

Miocene

Oligocene

Eocene

Paleocene

5

24

37

58

65



Earliest hominids



Earliest grasses

Earliest large
mammals
Cretaceous-Tertiary boundary (65 million years ago): extinction of dinosaurs
MesozoicCretaceous Upper

Lower



98

144





Earliest flowering
plants;
dinosaurs in
ascendance
Jurassic


Triassic


208


245

Earliest birds
& mammals

Age of Dinosaurs
begins
PaleozoicPermian

Carboniferous
Pennsylvanian
Mississippian


Devonian




Silurian


Ordovician

Cambrian

286


320
360


408




438


505

570



Earliest reptiles
Earliest winged
insects

Earliest vascular
plants (as ferns
& mosses)
& amphibians

Earliest land plants
& insects

Earliest corals

Earliest fish
ProterozoicPrecambrian

2500 Earliest colonial
algae & soft-bodied
invertebrates
Archean

4000 Life apears;
earliest algae &
primitive bacteria
*In millions of years before the present