The Himalayas represent a globally significant biodiversity hotspot, yet bryophyte diversity remains insufficiently explored, especially in some inaccessible areas. During recent field surveys in Motuo County, Xizang, China, we collected an unusual moss species resembling Scabridens E.B.Bartram but differing in gametophyte morphology, most notably by a short double costa. To clarify its taxonomic position, we assembled and annotated 20 complete chloroplast genomes from Cryphaeaceae, Leucodontaceae, and Pterobryaceae, and analyzed these alongside 29 additional Hypnales accessions. Comparative plastome analyses revealed conserved structures across these lineages, with minor variations in genome size, GC content, and IR boundary regions. Phylogenomic analyses revealed the unknown taxon as sister to S . sinensis E.B.Bartram with strong support. Morphologically, it differs from S . sinensis by a short double costa, leaf margins revolute from the base to near the apex, and longer setae. Both morphological and molecular evidence support the recognition of this unknown taxon as a new species, which we described here as S . gaochienii W.Z.Huang Y.Huan Wu. Furthermore, although Scabridens is sister to Cryphaeaceae in plastid phylogenies, its pronounced morphological distinctiveness supports the recognition of a new family, Scabridentaceae W.Z.Huang Y.Huan Wu, to accommodate the genus. Our results highlight the power of plastid phylogenomics in resolving complex relationships in Hypnales and underscore the eastern Himalayas as a priority region for bryophyte diversity exploration.
Huang et al. (Tue,) studied this question.