Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Thallus: foliose, 2-5 cm in diam., loosely adnate, subdichotomously to irregularly lobate lobes: irregular, +plane, separate, 1-5 mm wide, 50-100 µm thick, with an ascending margin; apices: rotund, entire to lacerate, often undulate, occasionally upturned upper surface: medium gray to brown, usually dull, smooth to short pubescent (often covered with arachnoid, anastomosing hairs), distinctly and irregularly wrinkled, not isidiate internal anatomy: with upper and lower cortices consisting of a single layer of irregularly isodiametrical cells, internally with loosely interwoven chains of Nostoc and hyphae lower surface: pale gray-blue, naked, smooth, with dense white tomentum of cylindrical hairs up to 1 mm long Apothecia: common, laminal, short stipitate to stipitate, 0.2-0.5 mm wide disc: brown, concave to plane margin: thalline, concolorous with the thallus, entire, pubescent exciple: euparaplectenchymatous, 10-45 µm thick centrally hymenium: hyaline below and thinly yellow above, 170-220 µm tall; paraphyses: unbranched, c. 1.5 µm wide, slightly inflated apically; subhymenium: yellow to pale brown, 25-70 µm thick asci: cylindrico-clavate, 8-spored ascospores: hyaline, muriform, 5-7-septate transversely, 1-2-septate longitudinally, ellipsoid to subfusiform, 27-50 x 12-18 µm, with acuminate ends Pycnidia: not observed Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: on bark in montane forests World distribution: SE Asia, East Africa, Canary Islands, North and South America Sonoran distribution: Arizona. Notes: Leptogium resupinans is an easily recognized species by its unusual hairs on the upper surface, that made Nylander believe that it fruited on the upturned lower surface (hence the epithet).