EON

ERA

PERIOD

EPOCH

TIME SPAN
(million years)

AGE of

Events

Phanerozoic

Cenozoic

Quaternary

Holocene

0-2

Mammals

Humans appear - Ice Ages - Mammals become abundant - Alps and Himalayas form

Pleistocene

Tertiary

Neogene

Pliocene

2-5

Miocene

5-24

Paleogene

Oligocene

24-37

Eocene

37-58

Paleocene

58-66

Mesozoic

Cretaceous

66-144

Reptiles

Flowering plants become abundant, diverse and abundant dinosaurs - major extinctions mark end of Cretaceous

Jurassic

144-208

First birds, abundant dinosaurs

Triassic

208-245

First dinosaurs and mammals

Paleozoic

Permian

245-286

Amphibians

Abundant small reptiles appear - major extinctions mark end of Permian

Carbon-
iferous

Pennsylvanian

286-320

Abundant insects, first reptiles - Widespread coastal swamps

Mississippian

320-360

Large primitive trees

Devonian

360-408

Fishes

First amphibians

Silurian

408-438

First land plant fossils

Ordovician

438-505

Marine Invertebrates

First Fish

Cambrian

505-545

1st shelled organisms,
Abundant and diverse marine life appears

Proterozoic

Grouped as Precambrian

545-2,500

Primitive Life

First multicelled organisms

Archean

2,500-3,800

First one-celled organisms - oldest fossils

Pre-Geologic Time

3,800-4,600

No geologic record on Earth