Thallus: foliose, 2-7 cm in diam., adnate, irregularly lobate lobes: very irregular, elongate, strongly thickened (swelling markedly when wet), often anatomosing, 1-2 mm wide, 150-600 µm thick; apices: rotund, thickened, entire or lobulate upper surface: medium gray to dark gray to almost black, usually dull, heavily lamellate longitudinally (not really wrinkled) internal anatomy: with upper and lower cortices consisting of a single layer of irregularly isodiametrical cells 5-9 µm in diam., internally with loosely interwoven chains of Nostoc and hyphae lower surface: pale to medium gray, wrinkled, with scattered tufts of white hairs Apothecia: common, submarginal towards lobe tips, sessile, 1-5 mm wide disc: brown to red-brown, concave to plane margin: thalline, concolorous with the thallus, entire or lobulate, heavily wrinkled exciple: euparaplectenchymatous, 70-130 µm thick centrally hymenium: hyaline below and thinly brown above, 115-200 µm tall; paraphyses: unbranched, 1-2 µm wide, slightly inflated apically; subhymenium: pale yellow to pale brown, 50-100 µm thick asci: cylindrico-clavate, 8-spored ascospores: hyaline, muriform, 3-5-septate transversely, 1-septate longitudinally, ellipsoid to subfusiform, 23-30 x 9-13 µm Pycnidia: not observed Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: common on bark of soft-barked oaks at intermediate elevations World distribution: pantropical and subtropical, occurring in North and South America, Africa, Australasia and Asia Sonoran distribution: infrequent in southern Arizona, Sinaloa, and Chihuahua. Notes: Leptogium phyllocarpum is characterized by its undulating, crisp lobes with lamellae on the upper surface, that swell considerably when wet. The only other, similar, fertile species is the rarer L. chloromelum, that is a much lighter greenish gray, more crustose, wrinkled species with a granular, rather than wrinkled or lobate thalline margin of the apothecia. Leptogium milligranum is potentially confusable as well due to its dark color, but it has granular isidia.