Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.

Thallus: closely adnate, foliose, lobate lobes: sublinear, contiguous, plane, narrow, 1-2 mm wide, apices truncate upper surface: brownish gray to brown, especially towards the tips, smooth, never pruinose, but also at least partly marginal pseudocyphellae: numerous, conspicuous, white, round to usually elongate to somewhat branched, laminal, reaching 0.5 mm soredia: granular, irregular, grayish white, often with bluish gray discoloration, originating from pseudocyphellae, marginal and laminal, up to 0.4 mm in diam., but joining into larger, linear or irregularly shaped structures lower surface: usually black centrally, brown marginally; rhizines: concolorous with the lower cortex Apothecia: absent in Sonoran material Pycnidia: absent Spot tests: upper cortex K+ yellow, C-; medulla K-, C+ rose Secondary metabolites: upper cortex with atranorin (minor or trace); medulla with gyrophoric acid (major) and orcinyl lecanorate (=decarboxygyrophoric acid) (minor). Substrate and ecology: on rocks from 460 m on San Clemente Island, California) to 2880 m (Hidalgo) World distribution: possibly cosmopolitan, known from North, Central and South America, Europe and Africa Sonoran distribution: Arizona and California (Channel Islands) .