stratigraphic intervals
   (System) †Cretaceous (145.0 - 66.0 Ma)
     (Series) †Upper (100.5 - 66.0 Ma)
       (Subseries) †Senonian
         (Stage) †Santonian (86.3 - 83.6 Ma)
           1 (Substage) †[upper]
           2 (Substage) †lower