"global chronostratigraphic units"
   (Eon) Phanerozoic Eon (541.0 Ma - present)
     1 (Era) †Paleozoic Era (541.0 - 251.902 Ma)
     2 (Era) †Mesozoic Era (252.17 - 66.0 Ma)
     3 (Era) Cenozoic Era (66.0 Ma - present)