stratigraphic intervals
   (System) †Carboniferous (358.9 - 298.9 Ma)
     (Series) †Upper
       (Stage) †Serpukhovian (330.9 - 323.2 Ma)
         1 (Substage) †Chokierian + Alportian
         2 (Substage) †Pendleian + Arnsbergian