Abstract
During the study of freshwater diatom communities in Hainan Province, China, we uncovered an unknown diatom species of the genus Decussiphycus, which is described as Decussiphycussinensis sp. nov. herein. The description is based on LM and SEM investigations; morphologically, the new species is compared to other taxa belonging to the genus. We complemented the description with the results of a molecular analysis based on SSU rDNA and rbcL sequencing. Molecular data is acquired for Decussiphycus for the first time. Hereby, we discuss the phylogenetic relationships between this genus and its closest allies - Aneumastus and Mastogloia, demonstrating the affinity of Decussiphycus within the order Mastogloiales.