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 Biddulphiophycidae Round & R.M. Crawford (1990) see Class Mediophyceae Medlin & Kaczmarska (2004)
         Order Hemiaulales Round & R.M. Crawford (1990)
           Family Hemiaulaceae Heib. (1863)
             1 Genus Eucampia Ehrenb. (1839)
             2 Genus Hemiaulus Heib. (1863)
             3 Genus Climacodium Grunow (1868)
             4 Genus Trinacria Heib. (1863)
             5 Genus Riedelta see Genus Riedelia Jousé & Shesh.-Por. (1971), nom. illeg.
             6 Genus Cerataulina H. Perag. ex F. Schütt (1896)
             7 Genus Pseudorutilaria Grove & Sturt (1886)
             8 Genus Baxteriopsis G. Karst. (1928)