stratigraphic intervals
   (System) †Jurassic (201.3 - 145.0 Ma)
     (Series) †Lower (201.3 - 174.1 Ma)
       (Stage) †Pliensbachian (190.8 - 182.7 Ma)
         1 (Substage) †margaritatus + spinatum Zones
         2 (Substage) †jamesoni-davoei Zones