Silurian

The Silurian was the period from the end of the Ordovician, about 443.4 million years ago (mya) to the beginning of the Devonian period, about 419 mya. It is the third period of the Paleozoic era and the Phanerozoic eon and the shortest period in the Paleozoic.

As with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by several million years. The beginning of the Silurian is set at a major extinction when 60% of marine species were wiped out, the End-Ordovician extinction event.