Thallus: foliose, tightly adnate to adnate, 2-8 cm in diam., irregularly lobate lobes: subirregular, plane to subconvex, separate, contiguous to +imbricate, 1.5-3 mm wide, not lobulate; apices: subrotund, smooth to crenate, eciliate upper surface: yellow-green, smooth, shiny, epruinose and emaculate, moderately to densely isidiate isidia: abundant, simple to rarely coralloid branched, initially subglobose but soon cylindrical, 0.07-0.1 mm in diam., 0.1-0.3 mm tall; tips: epicorticate, dull brown, often erumpent but not sorediate; soralia and pustulae absent medulla: white, with continuous algal layer lower surface: black, plane, moderately to densely rhizinate; rhizines: black, simple, 0.2-0.6 mm long Apothecia: common, substipitate, 2-8 mm wide, laminal on thallus; disc: cinnamon-brown to dark brown; margin: smooth, pruina absent asci: clavate, 8-spored ascospores: hyaline, simple, ellipsoid, 5-6 x 45 µm (according to Hale 1990) Pycnidia: not observed Spot tests: upper cortex K-, C-, KC-, P-; medulla K-, C-, KC-, P+ red Secondary metabolites: upper cortex with usnic acid (major); medulla with fumarprotocetraric acid (major). Substrate and ecology: on acidic rocks, usually in open, semi-arid to forested habitats World distribution: southeastern North America and extending to Chihuahua Sonoran distribution: occasional at intermediate elevations in Sonora and Chihuahua. Notes: This moderate-sized species is the only isidiate species with fumarprotocetraric acid in interior regions of the Sonoran area. Xanthoparmelia subramigera (Gyeln.) Hale, which also has fumarprotocetraric acid, occurs often in coastal areas of the Sonoran region, but it has a pale brown lower cortex, thicker isidia and a less adnate thallus. Although Hale (1990) describes the tips of the isidia as being syncorticate, the type has numerous isidia that are broken off and erumpent although not sorediate. The type corresponds exactly to our material.