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 Thalassiosirophycidae Round & R.M. Crawford (1990) see Class Mediophyceae Medlin & Kaczmarska (2004)
         Order Thalassiosirales Glezer & I.V. Makarova (1986)
           Family Cyclotellaceae see Family Stephanodiscaceae Glezer & Makarova (1986)
             1 Genus Cyclotella (Kütz.) Bréb. (1838)
             2 Genus Cyclostephanos Round (1987)
             3 Genus Stephanodiscus Ehrenb. (1845)