The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 million years ago (mya), to the beginning of the Devonian Period, about 416.0 ± 2.8 mya. 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. Base of Devonian Ludlow Epoch Paleozoic Era Силур Wenlock Epoch Silúrcio Gorstian Age Sheinwoodian Age Geologic Time Scale (2019) Llandovery Epoch シルル紀 Hirnantian Age Ordovician Period Rhuddanian Age Phanerozoic Eon a1.1.3.4 Early Devonian Epoch Sylur Silurian Period Silúrico Siluur Silūras younger bound -419.2 +|-3.2 Ma Late Ordovician Epoch Silur Silur Silur Silur Silur Silurien Ludfordian Age Devonian Period Siluuri Base of Silurian silur silur older bound -443.8 +|-1.5 Ma Homerian Age Lochkovian Age siluriano 志留纪 szilur Pridoli Epoch silúr Silurian Aeronian Age Telychian Age