"global chronostratigraphic units"
   (Eon) Phanerozoic Eon (541.0 Ma - present)
     (Era) †Paleozoic Era (541.0 - 251.902 Ma)
       (Period) †Cambrian Period (541.0 - 485.4 Ma)
         1 (Epoch) †Caerfai Epoch
         2 (Epoch) †Saint David's Epoch
         3 (Epoch) †Merioneth Epoch