| Era | Period | Epoch | Million Years Ago (MYA) | Characteristic Life |
| Cenozoic | Quaternary | Holocene (Recent) | .001 | Culmination of mountain building followed by erosion and moderate, short-lived invasions of continental margins by the seas. Rise of modern plants, animals, and man. Evolution of humans during the last 5-8 million years. Transition from archaic mammals to modern orders and eventually families. Early warming trends were reversed by the middle of the period to cooler and finally to glacial conditions. |
| Pleistocene | 1.8 |
| Tertiary | Pliocene | 5.3 |
| Miocene | 23.7 |
| Oligocene | 36.6 |
| Eocene | 57.8 |
| Paleocene | 66.4 |
| Mesozoic | Cretaceous | | 144 | Extensive mountain building at the end, climate cooled worldwide. Extinction of archaic birds and many reptiles by the end of this period. |
| Jurassic | 208 | First reptilian birds. Reptilian diversity was high in all habitats. Climate was warm and stable with little seasonal variation. |
| Triassic | 245 | Earliest dinosaurs, flying reptiles, marine reptiles. Primitive mammals appeared. Continents were high with few shallow seas. Climate warm. |
| Paleozoic | Permian | | 286 | Rise of primitive reptiles. Extinction of the trilobites. Climate was cold at the beginning but warmed progressively. Widespread extinctions at the end of this period. |
| Pennsylvanian | 330 | Earliest know insects, large arthropods. Climate generally warm and humid. Extensive coal producing swamps. Many specialized amphibians and the first appearance of reptiles. |
| Mississippian | 360 | Extinction of some fish lineages expansion of others. Beginning of large coal production swamps. Extensive radiation of amphibians. |
| Devonian | 408 | Explosion of fish and disappearance of many jawless varieties. First winged insects and tetrapods. Land was higher climate cooler. |
| Silurian | 438 | Earliest know land animals. Primitive plants. Rise of fishes. Abundant trilobites. |
| Ordovician | 505 | Earliest know vertebrates. Primitive plants. Trilobites and cephalopods abundant. |
| Cambrian | 550-590 | Extensive shallow seas. Brachiopods and trilobites common. |
Precambrian | Proterozoic | | 2,500 | Primitive water dwelling plants and animals. Changes in the lithosphere produced major land masses and shallow seas. |
| Archean | 4,600 | Oldest know life (mostly indirect evidence). Formation of the earth and slow development of the lithosphere, hydrosphere and atmosphere. Development of life in the hydrosphere. |
Adapted from Pough, F. H. 1996. Vertebrate life, 4thed. Prentice Hall. Upper Saddle River, NJ. Chart created by Arnold C. Mendez Sr. |