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)

ordovician

paleozoic