Selaginella guihaiasp. nov. (Selaginellaceae), a new species of spikemoss from southern China and northern Vietnam around the Gulf of Tonkin (Beibu Gulf), is described and illustrated. Morphological and molecular comparisons of the new species with other similar species (S. doederleinii, S. ornata and S. trachyphylla) are provided. The morphological and molecular evidence clearly indicates S. guihaia is a distinct species. Morphologically S. guihaia differs from other species by its obviously white-margined leaves, the ventral leaves scabrous on upper surfaces throughout the basiscopic or also rarely present on upper halves, and the ovate axillary leaves.
Keywords: ITS; Lycopodiophyta; lycophytes; new species; rbcL; taxonomy.