Paleozoic Era
Ordovician Period
485–444 Million Years Ago
The Ordovician saw a massive diversification of marine life, often called the Great Ordovician Biodiversification Event. Brachiopods, bryozoans, crinoids, and corals built the first extensive reef systems. The period ended with a severe glaciation and mass extinction that eliminated roughly 85% of marine species.
Environment
Climate & Environment
Initially warm, but ended with a major glaciation as Gondwana drifted over the South Pole. Sea levels dropped dramatically during the end-Ordovician ice age.
Fauna & Flora
Signature Life Forms
Brachiopods and bryozoans dominated seafloors
First coral reefs
Nautiloid cephalopods — major predators
Earliest land plants (non-vascular)
Collection
