Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Life habit: lichenicolous Thallus: crustose, areolate, up to 2 cm in diam., occasionally the inner areoles disintegrating; prothallus: black, dull, developing among the areoles areoles: peltate, highly convex, 0.3-0.8 mm wide surface: +bluish gray to dark gray cortex: thin, 5-15 µm thick, overlain with a thin epinecral layer up to 10 µm thick medulla: white, I+ blue-violet Apothecia: black, round disc: black; convex to strongly convex margin: lacking epihymenium: dark gray-brown, K+ red hymenium: hyaline, 100-140 µm tall; paraphyses: capitate; hypothecium: brown clavate, 8-spored ascospores: brown-black, almost opaque, muriform, ellipsoid, 16-32 x 9-16 µm Pycinidia: not seen Spot tests: medulla K-, C-, KC-, P- Secondary metabolites: unknown. Substrate and ecology: parasitic on Dimelaena oreina World distribution: western North America, Greenland and Europe Sonoran distribution: central Arizona. Note: Rhizocarpon renneri is very similar to R. eupetraeum and R. grande except for its parasitic habit.