Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.
Thallus: crustose, very thin, minutely granulose to almost powdery, usually forming very small patches, rarely somewhat spreading granules: irregularly shaped, 0.1-0.25 mm wide, ±diffuse or slightly aggregated upper surface: blackish, finely granulose, dull lower surface: attached by rhizohyphae Apothecia: single, ±hemispherical or slightly flattened on top, very small, 0.12-0.35 mm wide disc: punctiform, with shallow, persisting thalline margin proper exciple: very thin, up to 10 µm wide epihymenium: yellowish brown, K- hymenium: hyaline, 70-90 µm tall, IKI+ blue asci: subclavate, 8-spored ascospores: simple, hyaline, subglobose to broad ellipsoid, 8-15 x 5-9 µm; wall: thin Pycnidia: not observed conidia: not observed Spot tests: all negative Secondary products: none detected. Substrate and ecology: on calcareous rocks World distribution: Europe and SW North America Sonoran distribution: Arizona, southern California, and Baja California Sur. Notes: The intricate nomenclatural situation around the genera Psorotichia, Pyrenocarpon and Thelochroa was elucidated by Jørgensen and Henssen (1990b). However, because of the yet unsettled taxonomic position of Pyrenocarpon flotowianum (Hepp) Trevis. and Thelochroa montinii A. Massal., the latter species is treated here under Psorotichia following Forssell (1885). Psorotichia montinii is characterized by the very small and very thin, granulose to almost powdery thallus and minute apothecia with punctiform discs and flat margin.