Fossils and the geological timescale: Definition and Links by Encyclopedian.com

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 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)
- First flowering plants
- First primates
- Extinction of dinosaurs
- Extinction of ammonites
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