The following list gives the geologic timescale and its associated primary fossils.
- Precambrian (3.8 billion to 570 million years ago)
- Bacteria and blue-green algae
- Cambrian (570 to 500 million years ago)
- First invertebrates
- Ordovician (500 to 440 million years ago)
- Silurian (440 to 410 million years ago)
- First land plants
- First land invertebrates
- Devonian (410 to 365 million years ago)
- First ferns and seed plants
- First insects
- First amphibians
- Carboniferous (365 to 290 million years ago)
- First flying insects
- First reptiles
- Permian (290 to 245 million years ago)
- Triassic (245 to 210 million years ago)
- Extinction of trilobites
- First dinosaurs
- First mammals
- Jurassic (210 to 140 million years ago)
- First birds
- Cretaceous (140 to 65 million years ago)
- Paleocene (65 to 55 million years ago)
- Diversification and spreading of mammals
- Eocene (55 to 38 million years ago)
- Oligocene (38 to 25 million years ago)
- First grass
- Miocene (25 to 5 million years ago)
- Pliocene (5 to 2 million years ago)
- First hominids
