Medina Bujalance, RafaelFrancisco LaraVicente MazimpakaJames R. ShevockRicardo Garilleti2024-01-252024-01-252011-06-010007-27451938-437810.1639/0007-2745.114.2.316https://hdl.handle.net/20.500.14352/95391The stay was granted by the Spanish Ministry of Science and Innovation (FL) and the University of Valencia (RG). This work was funded by the Spanish Ministry of Education and Science, Grant CGL2007-61389.Orthotrichum pilosissimum is described from herbarium material and recently collected specimens in the state of Nevada. Its specific epithet refers to the diagnostic hyper-developed axillary hairs, which are frequently longer than 1 mm, multiseriate and branched, covering most of the stems surface and sometimes protruding from the foliose shoots. These hairs are not only unique in the genus but also among mosses, providing a reliable diagnostic character for the new taxon. Additional gametophytic and sporophytic characters that contribute to its taxonomic delimitation are also given.engjournal articlerestricted access582.32desert bryophytes, mosses, Orthotrichum tenellum, Orthotrichum bartramii, Orthotrichum norrisii, Western North America.Botánica (Biología)2417.01 Briología