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 throughout or loosely adnate and marginally ascending, 2-4 cm broad lobes: somewhat randomly to ± regularly arranged, contiguous to crowded or overlapping, narrow, 0.5-1 (-1.5) mm wide, strap-shaped to rounded, branched, sometimes quite dissected, margins deeply wavy to pinnate-cleft, tips often forked or dissected upper surface: whitish gray-green or ashy or darkening, smooth or becoming wrinkled toward center, somewhat shiny where smooth medulla: white, algal layer with Myrmecia lower surface: whitish to pale brown, somewhat wrinkled; rhizines scattered, brownish to brown Apothecia: usually present and often numerous and almost hiding thallus surface, often much wider than the lobes, 1.5-7 (-12) mm diam., sessile to shortly pedicellate, saucer-shaped; disc: concave to convex, yellowish to pale brown or chestnut brown to dark grayish brown, dull or slightly shiny, concolorous with thallus, or darker and browner next to the disc when young, raised or level, crenulate, persistent ascospores: subspherical to broadly ellipsoid, (5-) 6.5 (-8) x (3.5-) 4.5 (-6) micrometer Pycnidia: usually common, laminal or marginal Spot tests: cortex K+ yellow, C-, KC-, P-, medulla K+ deep yellow, C-, KC-, P+ deep yellow or orange, UV- Secondary metabolites: upper cortex with atranorin and chloroatranorin; medulla with thamnolic acid (major) and decarboxythamnolic acid (trace). Substrate and ecology: on conifer (rare on oak) bark, less often dead branches, in oak-pine-cypress and pine-oak woodlands and forests World distribution: eastern North America, central and southern Rocky Mountains, and northern plains Sonoran distribution: widely distributed and common in Arizona, Chihuahua, and Sonora, at 1600-3000 m. Notes: A somewhat similar species is the larger Heterodermia hypoleuca, but that species has a cottony, non-corticate lower surface and lacks thamnolic acid.