Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Mycelium: I- Apothecia: rare, superficial, 180-280 µm in diam. disc: black, epruinose when young, convex or slightly applanate hymenium: hyaline or pale brown, upper part K+ green hypothecium: yellowish brown, K- asci: elongate ellipsoid to clavate, 8-spored ascospores: brown, verrucose, 1-septate, cells slightly unequal, 1113.5(-14.5) x 4-5.5 µm Pycnidia: frequent, black, superficial, 90-200 µm in diam.; wall: brown, K+ yellow in upper part, 25-35 µm thick; conidiogenous cells: ampulliform to lageniform, 4-13 x 3-4.5 µm conidia: hyaline to pale yellow, obpyriform to ellipsoid, surface finely verruculose, almost appearing as smooth, 6.5-8.5 x 3.5-5.5 µm. Hosts: thallus of Flavoparmelia caperata; also reported from Flavopunctelia, Parmotrema, Punctelia and other parmelioid genera, but confirmation required World distribution: Europe and the U.S.A. Sonoran distribution: once collected in California. Notes: The pycnidia of Abrothallus microspermus are abundant on Flavoparmelia, where some scattered apothecia are sometimes found. The identity of the material reported from other genera (see above) can only be assessed in a convincing way when a modern revision of the genus is available.