Class Conjugatophyceae Engl. (1892) see Class Zygnematophyceae Round ex Guiry (2013) Order Zygnematales - filamentous conjugates and saccoderm desmids Family Mesotaeniaceae Genus Nucleotaenium A.A. Gontcharov & M. Melkonian (2010) 1 Nucleotaenium eifelense