Dicranum nepalense (Dicranaceae, Dicranales), a new species with fragile leaves from Nepal Himalayas

Dicranum Hedw. is a highly diverse and widely distributed genus within Dicranaceae, with over 95 species currently accepted. However, the species diversity and distribution of this genus in the Nepal Himalayas are still poorly understood. During our recent reexamination of older herbarium materials, we encountered intriguing specimens from Nepal annotated as “Dicranodontium nepalense”—a nomenclaturally invalid name due to the lack of a diagnosis and description when published. Here, we describe it as a new species, Dicranum nepalense W.Z.Huang, T.X.Zheng & Y.Huan Wu. This species is characterized by the fragile leaf apex, which is often absent in the lower portion of the plant; some leaves fractures at the base, with residual alar cells on the stem, forming a leafless section; a smooth leaf apex; rectangular, thick-walled, strongly porose laminal cells in the upper leaf portion; marginal cells narrower than the inner laminal cells, not porose; transverse section of the costa shows one row of guide cells and one row of slightly smaller cells below, without stereid bands; bistratose alar cells; and a differentiated central strand. In addition, a key for identification of the species of Dicranum with fragile leaves is provided.