The Silurian is a geologic period and system that extends from the end of the Ordovician period, about 443.7 ± 1.5 Ma (million years ago), to the beginning of the Devonian period, about 416.0 ± 2.8 Ma (ICS, 2004). 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 base of the Silurian is set at a major extinction event when 60% of marine species were wiped out. See Ordovician-Silurian extinction events.
Welsh Connection Edit
The Silurian period was named by Roderick Murchison for the Silures, an ancient tribe that lived in Wales, where Murchison first mapped Silurian-period rocks.