Phylum Ascomycota Caval.-Sm. (1998) - sac fungi
   Subphylum Pezizomycotina O.E. Erikss. & Winka (1997)
     Class Dothideomycetes O.E. Erikss. & Winka (1997)
       Family Mytilinidiaceae Kirschst. (1924)
         Genus Actidium Fr. (1815), nom. sanct.