Kingdom Protoctista Hogg, 1860
   Phylum Bacillariophyta Engl. & Gilg (1919) - diatoms see [unranked] Diatomea Kütz. (1844)
     Class Coscinodiscophyceae Round & R.M. Crawford (1990) - radial centrics
       Subclass Coscinodiscophycidae Round & R.M. Crawford (1990)
         Order Coscinodiscales Round & R.M. Crawford (1990)
           1 Family Coscinodiscaceae Kütz. (1844)
           2 Family Aulacodiscaceae (Schütt) Lemmerm. (1903)
           3 Family Gossleriellaceae Round (1990)
           4 Family Hemidiscaceae Hendey (1937)
           5 Family Actinoptychaceae see Family Heliopeltaceae H.L. Sm. (1872)