Eon Phanerozoic Eon

Phanerozoic Eon 28

• 538.8 Ma – 521 Ma Cambrian Explosion Most animal body plans appear Rapid diversification of complex multicellular life with hard body parts.
• 470 Ma First Coral Reefs Ordovician reef systems First significant coral-stromatoporoid reef systems in shallow Ordovician seas.
• 443.8 Ma End-Ordovician Extinction First major mass extinction Two-phase extinction driven by glaciation and sea level fall; ~85% of marine species lost.
• 430 Ma First Vascular Plants Life colonises the land Early plants like Cooksonia spread onto land.
• 385 Ma First Forests Devonian tree evolution Archaeopteris and Wattieza form first forests, dramatically altering the carbon cycle.
• 375 Ma First Tetrapods Fish crawl onto land Tiktaalik and relatives develop limbs and begin exploiting terrestrial environments.
• 372 Ma – 358.9 Ma Late Devonian Extinction Kellwasser and Hangenberg events Series of pulses over ~20 Ma; reef ecosystems collapse; ~75% of species lost.
• 335 Ma – 270 Ma Pangaea Assembles Supercontinent forms All major landmasses collide to form Pangaea.
• 312 Ma First Reptiles Amniote egg evolves Evolution of the amniotic egg frees vertebrates from dependency on water.
• 252.5 Ma – 251.5 Ma Siberian Traps Volcanism Triggers Great Dying Massive flood basalt volcanism releases CO2 and SO2, causing runaway climate change.
• 251.902 Ma End-Permian Extinction The Great Dying — 96% of marine species lost Largest mass extinction; caused by Siberian Traps volcanism, ocean acidification and anoxia.
• 231 Ma First Dinosaurs Triassic origin of dinosaurs Earliest dinosaurs appear in South America after the P-T extinction recovery.
• 225 Ma First Mammals Tiny Triassic ancestors Small insectivorous mammals appear alongside early dinosaurs.
• 201.4 Ma End-Triassic Extinction CAMP volcanism Massive volcanism as Pangaea rifts apart; ~80% of species lost; clears way for dinosaur dominance.
• 201 Ma – 140 Ma Pangaea Breaks Apart Atlantic Ocean opens Pangaea rifts apart; Atlantic begins to open.
• 150.8 Ma Archaeopteryx First known bird Transitional fossil combining dinosaur and bird features; Jurassic Solnhofen limestone, Germany.
• 130 Ma First Flowering Plants Angiosperms diversify Flowering plants appear and co-evolve with insects, eventually dominating terrestrial ecosystems.
• 120 Ma – 90 Ma Ocean Anoxic Events Cretaceous dead zones Repeated episodes of ocean-wide anoxia during the Cretaceous.
• 66.5 Ma – 65.5 Ma Deccan Traps Volcanism Contributes to K-Pg extinction Large volcanic province erupting around Chicxulub impact, compounding extinction pressures.
• 66 Ma Chicxulub Impact Asteroid ends the Mesozoic 10 km asteroid strikes Yucatan; triggers mass extinction.
• 66 Ma End-Cretaceous Extinction K-Pg event — dinosaurs go extinct Chicxulub asteroid impact ends the Mesozoic. Non-avian dinosaurs, mosasaurs and ammonites disappear.
• 56 Ma – 55.8 Ma Paleocene-Eocene Thermal Maximum PETM — rapid global warming Global temperatures rise 5-8 C in under 20,000 years; closest ancient analogue to modern climate change.
• 53 Ma First Whales Return to the sea Pakicetus and relatives begin transitioning from land to aquatic life.
• 33.9 Ma – 33.7 Ma Antarctic Ice Sheet Forms Eocene-Oligocene transition Drake Passage opens; cold circumpolar current drives Antarctic glaciation.
• 6 Ma – 4 Ma First Hominids Apes walk upright Early hominins appear in Africa; bipedal locomotion evolves.
• 3 Ma – 2.8 Ma Panama Land Bridge Closes Atlantic and Pacific separate Central American seaway closes; alters ocean circulation and intensifies glaciation.
• 2.58 Ma – 0.012 Ma Pleistocene Ice Ages Repeated glacial cycles Glacials and interglacials driven by Milankovitch cycles; ice sheets cover North America and Europe.
• 0.3 Ma – present Homo sapiens Modern humans evolve Anatomically modern Homo sapiens appears in Africa, eventually spreading to every continent.