Kingdom Protoctista Hogg, 1860
   Phylum Bacillariophyta Engl. & Gilg (1919) - diatoms see [unranked] Diatomea Kütz. (1844)
     Class Bacillariophyceae Haeckel (1878) - pennates
       Subclass Bacillariophycidae D.G.Mann (1990) - raphid diatoms
         Order Surirellales D.G.Mann (1990)
           Family Surirellaceae Kütz. (1844)
             Genus Plagiodiscus Grunow & Eulenst. (1867)