"global chronostratigraphic units"
   (Eon) Phanerozoic Eon (541.0 Ma - present)
     (Era) Cenozoic Era (66.0 Ma - present)
       (Sub-era) Quaternary Sub-era (2.58 Ma - present) see Period Quaternary Period (2.58 Ma - present)
         1 (Period) Pleistogene Period see Period Quaternary Period (2.58 Ma - present)