﻿AbstractA new species of spikemoss,SelaginelladensiciliatainS.subg.Heterostachyssect.Tetragonostachyae, China, is described from southeastern Xizang, based on morphological and molecular phylogenetic data. Morphologically,S.densiciliatais similar toS.repanda,S.subvaginataandS.vaginata, but the new species can be easily distinguished from them by having sterile leaves margins densely ciliate, symmetrical axillary leaves oblong ovate to ovate-triangular, and ovate dorsal leaves obviously carinate. Molecular phylogenetic analysis resolvesS.densiciliataas sister to the clade comprised withS.vaginataandS.xipholepis, which confirms the recognition of the new species.