Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.

Thallus: foliose, 1-7 cm in diam., adnate, subdichotomously to irregularly lobate lobes: irregular, elongate, +plane, thick, separate to often imbricate, 1-6 mm wide, 150-250(-500) µm thick; with an ascending margin; apices: rotund, usually entire to irregularly cut or lobulate, occasionally upturned upper surface: medium gray or bluish gray to brown or blackish brown, usually dull, distinctly and irregularly wrinkled, not isidiate 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 or brown, wrinkled, with scattered tufts of white hairs Apothecia: common, laminal, sessile to short stipitate, 0.2-0.5 mm wide disc: brown, concave to plane margin: thalline, concolorous with the thallus, entire 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, 7-9-septate transversely, 1-2-septate longitudinally, ellipsoid to subfusiform, 35-48 x 9-16 µm Pycnidia: not observed Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: on soil or rocks World distribution: western North America and India Sonoran distribution: southern California and Chihuahua. Notes: Leptogium platynum is robuster and thicker than L. californicum or L. gelatinosum and has generally larger spores than those two species.