The geological time system is arranged in a hierarchical fashion, with Eon Era Period Epoch The Geological Timetable Precambrian Eon 590 million - 4.5 billion years ago From the formation of the earth to the explosion of multicellular life 4.5 billion years ago (BYA): Earth formed 3.8 BYA Oldest terrestrial rocks 3.5 BYA Earliest clear evidence of fossil bacteria 2.5 BYA Origin of aerobic photosynthesis, creation of oxygen-rich atmosphere 1.5 BYA First clear evidence of eukarytoic fossils 1.0 BYA Protists (single-celled eukaryotes) diversify 0.8 BYA Earliest clear traces of fossil invertebrates Phanerozoic Eon 590 MYA to present: The diversification of multicellular life Paleozoic Era 590 -248 MYA Fishes and amphibians dominate Mesozoic Era 248 - 65 MYA Dinosaurs dominate Cenozoic Era 65 MYA - present mammals dominate Paleozoic Era Cambrian Period 590-505 MYA Explosive evolution of most major phyla Mass extinction event at Cambrian-Ordovician boundary Ordovician Period 505-438 MYA Silurian Period 438-408 MYA First fossil jawed fishes Plants colonize the land Devonian Period 408-360 MYA Age of fishes Carboniferous Period 360-280 MYA Vast forests appear on land Amphibians appear on land Permian Period 280-248 MYA Conifers appear Mesozoic Era Triassic Period 248-213 MYA Extinction of trilobites Mammals and dinosaurs appear Jurassic Period 213-144 MYA Dinosaurs diversify Archaeopteryx, first fossil bird, appears Cretaceous Period 144-65 MYA Angiosperms appear and become the dominate terrestrial plant form Mass extinction at Cretaceous-Tertiary boundary, evidence of extra-terrestrial impact Cenozoic Era Tertiary Period 65 - 2.5 MYA Paleocene Epoch 65 -55 MYA Eocene Epoch 55 -38 MYA Oligocene Epoch 38 -26 MYA Miocene Epoch 26 - 6 MYA Earliest primates Pliocene Epoch 6-2.5 MYA Origin of hominids Quaternary Period 2.5 MYA - present Pleistocene Epoch 2.5 MYA - 10,000 years ago Origin of Homo Recent Epoch 10,000 years ago - present