Ordovician · 485.4 – 443.8 Ma

Ordovician fossil sites

The Ordovician was a period of warm seas and explosive marine diversification. Trilobite morphology became extravagant; the first true reef-building corals appeared; nautiloid cephalopods grew to over five meters. The period ended with one of the largest mass extinctions in Earth's history.

21 fossil sites

Updated 27 July 2026