ABSTRACT Three simple filamentous cyanobacteria (strains S1, S6 and S10) were isolated from the upper surface of intertidal soil of an Indian mangrove forest, the Sundarbans. The three cyanobacterial strains formed a new cluster within the phylogenetic tree calculated based on 16S rRNA gene sequences, which was distinctive from the clade of the ecologically and morphologically most similar genus, Euryhalinema. Moreover, the sequence similarity of 16S rRNA gene was less than 94.4% compared with the reference strain of Euryhalinema, which confirmed that the new strains belonged to a novel genus. The folded secondary structure of D1-D1’, Box-B and V3 helices of the internal transcribed spacer (ITS) region were different from those of Euryhalinema and other members of family Nodosilineaceae. P-distance analysis of the ITS region of the test strains showed 22.2% dissimilarity with the reference genus Euryhalinema, which exceeded the cut off (7%) and strongly supported that it is a novel species within a novel genus. Differential morphological and ultrastructural characters, such as the presence of various cellular inclusions (prominent large cyanophycin granule, glycogen α granules, lipid β granules and mucilaginous sheath), conical-shaped apical cell as well as cell width, supported the description of a new taxon. Therefore, based on morphological, ultrastructural and molecular analysis we propose that cyanobacterial strains S1, S6 and S10 belong to a new monophyletic genus and species Almyronema epifaneia gen. & sp. nov., in the recently established family Nodosilineaceae.