Kumanoa belonging to the order Batrachospermales is the most species-rich and widely distributed genus of freshwater red algae in China. In this study, a new Kumanoa species is described and illustrated from Baiyun Mountain, Guangdong, China, based on morphological observations and phylogenetic analysis. Kumanoa baiyunensis sp. nov is morphologically distinguished from other species by presenting a small habit (0.5–1 cm tall) with abundant branching in upper part of the thallus; carposporophytes spherical and one per whorl; club-shaped trichogynes with distinct stalk; spermatangia sparse and single-grown, terminal on primary fascicles. Phylogenetic analysis based on the concatenated rbcL+COI-5P+UPA alignment places Kumanoa baiyunensis in a well-supported clade (98/0.96, bootstrap proportion/posterior probability) sister to K. faroensis (from USA) and K. spermatiophora (from Hawaii) with high divergence (rbcL: 4.9%–5.0%, COI-5P: 10.1%–10.5%, UPA: 2.3%). In addition, K. baiyunensis can be easily distinguished from ten Kumanoa species reported in China through morphological features such as small thallus size, abundant branching in upper parts of the thallus, and spermatangia sparse, single-grown, and terminal on primary fascicles. The description of this new species expands the diversity of genus Kumanoa in the world.
