"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)
           1 (Stage) †Rhuddanian Stage (443.8 - 440.8 Ma)
           2 (Stage) †Aeronian Stage (440.8 - 438.5 Ma)
           3 (Stage) †Telychian Stage (438.5 - 433.4 Ma)