Encyonema meghamalaiense sp. nov. (Bacillariophyceae, Encyonemataceae): A New Cymbelloid Diatom from the Meghamalai Hills, Tamil Nadu, India

Diatom taxonomy has undergone significant revisions, particularly within the order Cymbellales, where species boundaries remain challenging due to transitional morphological characters and emerging new insights from molecular data. In this study, Encyonema meghamalaiense sp. nov. is described from the Meghamalai Hills, Western Ghats, Tamil Nadu, India. This species is characterised by its asymmetric, lanceolate valves with subcapitate apices. The striation is irregular, becoming uniseriate to biseriate near the apices. While it shares similarities with Encyonema keshrii in the areolae pattern, it differs in valve outline and raphe structure, highlighting its taxonomic distinction. Given the taxonomic complexity of the Encyonema—Encyonopsis—Kurtkrammeria complex, detailed comparative morphological assessments were conducted to clarify its classification using a light and scanning electron microscope. These findings contribute to the growing understanding of species diversity within Encyonemataceae and underscore the need for further integrative taxonomic studies to resolve complex species boundaries in this group, especially from the tropics.