Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2002. Lichen Flora of the Greater Sonoran Desert Region. Vol 1.

Thallus: foliose, adnate, orbicular, irregularly rosetted and spreading, 2-8 cm diam., lobate, with mostly contiguous to overlapping lobes lobes: up to c. 2.5 cm long, 0.5-1 mm broad, terete, or the main ones flattened when on stone, becoming crenate to incised or irregularly branched laterally or towards tips, partly also with ± sparse, discrete, narrow (0.2-0.5 mm) branches or lobules, which arise ± perpendicularly to the tips or margins, or towards the thallus center, and are often more terete and nodulose than the main branches upper surface: epruinose, pale gray, ashy gray, or brown, darkening or blackening especially on the lobules and towards the tips, and there becoming shiny, with conspicuous, reticulate whitish-yellowish maculae at least in the apical 2-3 mm of the lobes or lobules, with the darker areas between the maculae often slightly depressed (shallowly sulcate); otherwise mostly plane, smooth, dull, continuous to irregularly and finely cracked [in material from outside the Sonoran region, becoming distinctly areolate with discontinuous patches of cortex interspersed with black cracks and lines, Thomson 1984] medulla: white, solid lower surface: black, brown toward the tips, with occasional coarse transverse cracks, smooth to ± irregularly, weakly, and shallowly wrinkled to plicate or foveolate Apothecia: rare [not seen in material from Sonoran region], up to 5 mm diam., with a thin, entire thalloid margin; disc: dark brown ascospores: subglobose to broadly ellipsoid, 10-12 x 8 µm Pycnidia: numerous, conspicuous under lens, immersed, the visible part black to gray-brown, roundish, < c. 0.5 mm diam Spot tests: cortex K+ yellow, C-, KC-, P+ yellow; medulla K-, C-, KC+ red, P+ orange in layer close to cortex in apices only, or P- Secondary metabolites: cortex with atranorin and chloroatranorin, medulla with physodic acid (major) and with protocetraric acid (accessory). Substrate and ecology: alpine, on highly insolated rocks and over mosses in places with winter snow cover World distribution: circumpolar, arctic and northern boreal and alpine regions to the south Sonoran distribution: known only from the alpine zone of the San Francisco Peaks near Flagstaff, Arizona.