stratigraphic intervals
   (System) †Tertiary (66.0 - 2.58 Ma)
     (Subsystem) †Paleogene (66.0 - 23.03 Ma) see System Paleogene System (66.0 - 23.03 Ma)
       (Series) †Paleocene (66.0 - 56.0 Ma)
         (Stage) †Thanetian (59.2 - 56.0 Ma)
           1 (Substage) †Upper
           2 (Substage) †Lower