Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Life habit: lichenized, not lichenicolous Thallus: crustose, immersed in the host thallus or areolate; prothallus: poorly to well developed areoles: round to angular, sometimes indistinctly effigurate, weakly convex to bullate, up to 0.8 mm in diam. surface: bright yellow, smooth or scabrose, epruinose medulla: white, KI+ faintly violet Apothecia: round or angular, up to 0.6 mm in diam. disc: black, weakly convex or strongly convex, epruinose margin: lacking epihymenium: brown, not containing crystals, K+ red hymenium: hyaline, 60-90 µm tall; paraphyses: tips fused into a pseudoparenchymatous tissue; hypothecium: brown asci: clavate, 8-spored ascospores: black, ellipsoid, 12-18 x 5-10 µm Spot tests: medulla K-, C-, KC-, P+ yellow Secondary metabolites: rhizocarpic acid, often psoromic acid and sometimes traces of stictic acid. Substrate and ecology: on non-calciferous often vertical rock in spruce-fir zone above 3000 m Host: Pleopsidium flavum World distribution: Europe and North America Sonoran distribution: Arizona (San Francisco Peaks, Mt. Baldy). Notes: Sonoran material is lichenicolous on Pleopsidium flavum. The species may also be autonomous, and such specimens differ from R. superficiale mainly in forming smaller, slightly effigurate thalli and in having a KI+ faintly violet medulla. The Sonoran material lacks psoromic and stictic acid, which occur, e.g., in material from Colorado and Montana.