| Era |
Period |
Start Time |
Notes |
| Cenozoic |
Quarternary |
2 million years ago |
Ice Age, modern humans |
| Tertiary |
66 million years ago |
abundant mammals |
| Mesozoic |
Cretaceous |
144 million years ago |
first flowering plants;
extinction of dinosaurs |
| Jurassic |
208 million years ago |
first birds; abundant dinosaurs |
| Triassic |
257 million years ago |
first dinosaurs and
mammals; conifer forests |
| Paleozoic |
Permian |
297 million years ago |
extinction of trilobytes and other marine
animals |
| Pennsylvanian |
323 million years ago |
first reptiles; fern
forests; abundant insects |
| Mississippian |
360 million years ago |
large primative trees |
| Devonian |
415 million years ago |
first amphibians; fish
diversify |
| Silurian |
438 million years ago |
early plants and animals on land |
| Ordovician |
490 million years ago |
jawless armored fish |
| Cambrian |
543 million years ago |
first abundant shelly invertibrates |
| Precambrian |
Proterozoic |
2500 million years
ago |
one-cell organisms (bacteria,
protists) |
| Archean |
4600 million years ago |
oldest fossils; origin of the Earth |
