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DescriptionThallus: foliose, 2-5(-10) cm in diam., adnate, subdichotomously to irregularly lobate; lobes: irregular, somewhat elongated, separate, 2-10 mm wide, 100-200(-300) µm thick; apices: rotund, entire to irregularly cut and isidiate, occasionally upturned; upper surface: usually medium gray but sometimes brownish gray, usually dull, quite wrinkled (never really smooth), +plane; isidia: usually dense, laminal to marginal, usually cylindrical to flattened and may become squamiform, simple or occasionally branched, concolorous with the thallus or darker; internal anatomy: with upper and lower cortices consisting of a single layer of irregularly isodiametrical cells 4-8 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: rare, laminal, sessile, 0.5-2 mm wide; disc: light brown to more usually red-brown, concave to plane; margin: thalline, concolorous with the thallus or cream-colored, entire or isidiate; exciple: euparaplectenchymatous, often poorly developed, 15-100 µm centrally; hymenium: hyaline below and thinly brown above, 95-125 µm tall; paraphyses: unbranched, c. 1.5 µm wide, slightly inflated apically; subhymenium: yellow to pale brown, 45-90 µm thick; asci: cylindrico-clavate, 8-spored; ascospores: hyaline, 35-septate transversely, 0-1-septate longitudinally, ellipsoid, 15-27 x 7-9 µm; Pycnidia: not observed; Spot tests: all negative; Secondary metabolites: none detected.; Substrate and ecology: on bark in subtropical habitats; World distribution: North and South America, Australasia and East Africa; Sonoran distribution: Arizona, Baja California Sur and Chihuahua.; Notes: Leptogium austroamericanum is often confused with the variable L. cyanescens, but clearly is different in its usually thicker, always wrinkled thallus. The former species is more subtropical and the latter species more temperate in their respective distributions.