Eon

Era

Period

Epoch

Years Ago

Age of

Significant Events

Phanerozoic

Cenozoic

Quaternary

Holocene

0-11,000

Mammals

Human

Civilization

Pleistocene

11,000-2 million

Ice Age

Tertiary

2-66

million

Extinction of Dinosaurs

Mesozoic

Cretaceous

66-144

million

Reptiles

Flowering Plants

Jurassic

144-208

million

Birds and Mammals

Triassic

208-245

million

Dinosaurs

Paleozoic

Permian

245-286

million

Amphibians

Extinction of Trilobites

Carboniferous

286-320

million

First Reptiles and Large Primitive Trees

Devonian

260-408

million

Fishes

First Amphibians

Silurian

408-438

million

First Land Plant Fossils

Ordovician

438-505

million

Invertebrates

First Fish

Cambrian

505-570

million

First Shells-Trilobites Dominate

Proterozoic

Also known as the Precambrian

570 million-

2.5 billion

First Multi-celled Organisms

Archean

2.5- 3.8

billion

First One-celled Organisms

Hadean

3.8-4.6

billion

Approximate age of oldest known rocks