Thallus: foliose, 1-5(-8) cm in diam., adnate, subdichotomously to irregularly lobate lobes: irregular, elongate, +plane to slightly roughened (but not wrinkled), separate, 2-4 mm wide, 35-110µm thick; apices rotund, entire, dentate to irregularly cut and isidiate, occasionally upturned upper surface: light to medium gray, usually dull, smooth to somewhat wrinkled isidia: usually dense, laminal to marginal, usually cylindrical to flattened and may become lobulate, simple but usually becoming branched, concolorous with the thallus or darker internal anatomy: with upper and lower cortices consisting of a single layer of irregularly isodiametrical cells 5-8 µm in diam., internally with loosely interwoven chains of Nostoc and hyphae lower surface: light to medium gray, smooth, with scattered tufts of white hairs Apothecia: occasional, laminal, sessile to substipitate, 0.5-2 mm wide disc: light brown to more usually red-brown, slightly concave to plane to convex margin: thalline, concolorous with the thallus or cream-colored, entire or isidiate exciple: euparaplectenchymatous, often poorly developed centrally hymenium: hyaline below and thinly brown above, 95-130 µm tall; paraphyses: unbranched, c. 1 µm wide, slightly inflated apically; subhymenium: pale yellow, 45-80 µm thick asci: cylindrico-clavate, 8-spored ascospores: hyaline, 3-septate transversely, 0-1-septate longitudinally, ellipsoid to fusiform, 18-23 x 6-10 µm Pycnidia: not observed Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: particularly common on bark of soft-barked oaks and junipers at intermediate elevations World distribution: pantropical and pantemperate, throughout North America, especially in the south, Australasia, Europe, Asia and East Africa Sonoran distribution: central and southeastern Arizona, Sinaloa and Baja California Sur. Notes: Morphologically the bluish gray L. cyanescens is most similar to the olivaceous brown L. dactylinum Tuck. in Nyl., that is not yet known from the Sonoran region. The latter species usually has smaller, more squamiform lobes and is more abundantly fertile than L. cyanescens.