Thallus: foliose, 2-5(-8) cm in diam., adnate, subdichotomously to irregularly lobate lobes: irregular, somewhat elongated, +plane, separate, 2-4 mm wide, (130-)200-350 µm thick; apices rotund, entire to irregularly cut, occasionally upturned upper surface: usually dark brown to olivaceous brown but sometimes medium to dark gray, shiny, strongly ridged periclinally, not isidiate internal anatomy: with upper and lower cortices consisting of a single layer of irregularly isodiametrical cells 5-7 µm in diam., internally with loosely interwoven chains of Nostoc and hyphae lower surface: pale to medium brown, wrinkled, with dense white tomentum of cylindrical hairs up to 1 mm long Apothecia: abundant, laminal, sessile, 0.4-2(-3) mm wide disc: light brown to more usually red-brown, plane to slightly convex margin: thalline, concolorous with the thallus, entire or isidiate exciple: euparaplectenchymatous, 25-45 µm centrally hymenium: hyaline below and thinly brown above, 90-105 µm tall; paraphyses: unbranched, c. 1.5 µm wide, slightly inflated apically; subhymenium: pale yellow, 35-45 µm thick asci: cylindrico-clavate, 8-spored ascospores: hyaline, muriform, 3-4(-5)-septate transversely, 0-septate longitudinally, fusiform, 30-40 x 6-7 µm Pycnidia: not observed Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: occasional on bark of soft-barked oaks at intermediate elevations World distribution: southwestern North America and Japan Sonoran distribution: southeastern Arizona, Sonora and Chihuahua. Notes: In contrast to the more common L. pseudofurfuraceum, L. rugosum lacks isidia, although both are brown. In addition, the fusiform, transversely septate spores of L. rugosum contrast with the submuriform spores of L. pseudofurfuraceum. Its brownish thallus and fusiform spores separate it from the more bluish L. acutisporum.