"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) †Wenlock Epoch (433.4 - 427.4 Ma)
           1 (Stage) †Sheinwoodian Stage (433.4 - 430.5 Ma)
           2 (Stage) †Whitwellian Stage
           3 (Stage) †Gleedonian Stage