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 |
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 . | ||