Division Bacillariophyta Engl. & Gilg (1919) see Phylum Bacillariophyta Engl. & Gilg (1919)
   Class Fragilariophyceae Round (1990) - araphid, pennate diatoms see Class Bacillariophyceae Haeckel (1878)
     Subclass Fragilariophycidae Round (1990) - core araphid diatoms
       Order Thalassionematales Round (1990)
         Family Thalassionemataceae Round (1990)
           1 Genus Thalassionemaᵀ (Grunow ex H. Perag. & Perag.) Perag. (1921)
           2 Genus Thalassiothrix Cleve & Grunow (1880)
           3 Genus Trichotoxon F. Reid & Round (1988)