"global chronostratigraphic units" (Eon) Phanerozoic Eon (541.0 Ma - present) (Era) †Paleozoic Era (541.0 - 251.902 Ma) (Period) †Silurian Period (443.8 - 419.2 Ma) (Epoch) †Llandovery Epoch (443.8 - 433.4 Ma) (Stage) †Rhuddanian Stage (443.8 - 440.8 Ma)