Division Bacillariophyta Engl. & Gilg (1919) see Phylum Bacillariophyta Engl. & Gilg (1919)
   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 Thalassiosiraceae M. Lebour (1930), nom. cons.
           1 Genus Thalassiosira Cleve (1873)
           2 Genus Planktoniella Schütt (1893)
           3 Genus Porosira Jørg. (1905)
           4 Genus Minidiscus Hasle (1973)
           5 Genus Bacteriosira Gran (1900)