| era | period | epoch | features | began years before the present (bp) |
|---|---|---|---|---|
| Cenozoic | Quaternary | Holocene (Recent) | modern humans | 10,000 |
| Pleistocene | Early humans, glaciation | 2,000,000 | ||
| Tertiary | Pliocene | mammals | 5,000,000 | |
| Miocene | 24,000,000 | |||
| Oligocene | 37,000,000 | |||
| Eocene | 55,000,000 | |||
| Paleocene | 65,000,000 | |||
| Mesozoic | Cretaceous | reptiles | 140,000,000 | |
| Jurassic | dinosaurs | 200,000,000 | ||
| Triassic | reptiles, early dinosaurs | 225,000,000 | ||
| Paleozoic | Permian | amphibians | 280,000,000 | |
| Pennsylvanian | 320,000,000 | |||
| Mississippian | 350,000,000 | |||
| Devonian | fishes | 400,000,000 | ||
| Silurian | 430,000,000 | |||
| Ordovician | marine invertebrates | 500,000,000 | ||
| Cambrian | trilobites | 570,000,000 | ||
| Precambrian | abundant fossils through formation of earth | 4,600,000,000 | ||