Kingdom Protoctista Hogg, 1860
   Phylum Rhodophyta Wettst. (1901) - red algae
     Class Rhodophyceae Thuret (1855) - red algae see Phylum Rhodophyta Wettst. (1901)
       Genus Porphyridium Nägeli (1849), nom. cons.
         1 Porphyridium cruentum (Gray) Nägeli