Thallus: erect-shrubby, tufted, 2-7 cm long branching: the whole thallus anisotomic-dichotomous basal part: paler than or concolorous to branches or ±pale brown branches: tapering; lateral branches: distinctly narrowed at attachment point segments: terete, ±cylindrical to strongly sausage-like papillae/tubercles: verrucous, few to numerous, irregularly distributed fibercles: usually absent fibrils: few to numerous, short (< 3mm) and thick, spinulous, unevenly distributed on the whole thallus, often numerous on the apices, giving a spinulous aspect to the terminal part of the thallus soralia and isidiomorphs: absent pseudocyphellae: absent cortex: thin (3-7%), shiny medulla: moderately thick to thick, lax to dense central axis: thin to moderately thick Apothecia: usually numerous, terminal or lateral ascospores: elliptical, 9-12 x 6-8 µm Spot tests: K+ dull yellow turning reddish orange, C-, KC-, P+ deep yellow Secondary metabolites: norstictic acid (major), ±salazinic acid (major). Substrate and ecology: on bark, on Abies spp., Quercus spp. and Pinus spp. in the temperate forests in mountainous area between 1500 and 3650 m World distribution: North and South America Sonoran distribution: Arizona and southern California. Notes: Usnea cirrosa is distinguished by its lateral branches that are distinctly constricted at ramification points, its swollen branch segments, its thin and shiny cortex and the numerous apothecia. Usnea cirrosa can be considered as the primary species of U. cornuta. It is closely related to if not identical to U. ramillosa Motyka that produces protocetraric acid in the medulla instead of norstictic acid in U. cirrosa. There is probably the same relationship between U. cirrosa and U. ramillosa as occurs between U. cornuta and U. brasiliensis. Therefore, I propose the new combination Usnea cirrosa: subsp.