stratigraphic intervals
   (System) †Tertiary (66.0 - 2.58 Ma)
     1 (Subsystem) †Neogene (23.03 - 2.58 Ma) see System Neogene System (23.03 - 2.58 Ma)
     2 (Subsystem) †Paleogene (66.0 - 23.03 Ma) see System Paleogene System (66.0 - 23.03 Ma)