[Parmelia saxatilis var. leucochroa Wallr., more, Parmelia sulcata var. laevis Nyl., Parmotrema sulcatum (Taylor) M. Choisy, Parmotrema sulcatum var. contorta (Bory) M. Choisy, Parmotrema sulcatum var. pruinosa (Harm.) M. Choisy, Parmotrema sulcatum var. sulcatum (Taylor) M. Choisy]
Thallus: adnate, foliose, 4-20 cm in diam., lobate lobes: sublinear, contiguous to imbricate, elongate, plane, separate, 2-4 mm wide, apices truncate upper surface: gray, smooth to strongly foveolate, shiny, sometimes white pruinose, becoming cracked along prominent, effigurate pseudocyphellae soredia: granular, abundant, laminal, in linear soralia; isidia, pustulae and dactyls absent medulla: white with continuous algal layer lower surface: black, rhizinate; rhizines moderately dense, black, simple Apothecia: rare, laminal, 2-8 mm wide; margin: usually sorediate; disc: dark brown asci: clavate, 8-spored ascospores: ellipsoid, 11-14 x 6-8 µm Pycnidia: infrequent, immersed conidia: bacilliform, 6-8 x 1 µm Spot tests: upper cortex K+ yellow, C-, KC-, P+ yellow; medulla K+ yellow turning deep red, C-, KC-, P+ orange Secondary metabolites: upper cortex with atranorin and chlorotranorin; medulla with salazinic acid (major) and consalazinic acids (minor). Substrate and ecology: common on trees in open habitats, occasionally on rocks World distribution: pantemperate and southern boreal Sonoran distribution: relatively common on deciduous and coniferous trees in montane habitats of Arizona, on coastal oaks in California and on rocks in the high mountains of northern Baja California.