Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.

Life habit: lichenicolous, on thallus of Phaeophyscia species Thallus: inapparent photobiont: absent Ascomata: breaking through the upper cortex of the host, ±round, 0.12-0.25 mm wide disc: black, parts of the epinecral layer of the host remaining on the ascomata epihymenium: pale olivaceous brown, 10-25 µm thick; cells: c. 7 x c. 4 µm hymenium: hyaline, 30-35 µm tall; paraphysoids: vertically oriented, branched and anastomosed; subhymenium: hyaline to pale brown, K+ pale gray, 20-25 µm thick asci: clavate, 25-38 x 12-18 µm, 8-spored, with thin lateral walls ascospores: hyaline, 1-septate (indistinctly constricted at the septum), obovate, 12-14 x 4-6 µm, smooth, with an epispore Pycnidia: not observed Chemical reactions: ascomatal gels I+ red; asci with KI+ blue ring-structure. Substrate and ecology: see host World distribution: probably the same as the host Sonoran distribution: Arizona (Gila Co.) and Baja California Sur. Notes: Arthonia phaeophysciae is easily distinguished from Arthonia epiphyscia, another species on members of the Physciaceae, by its ontogeny in the uppermost layers of the host, through which it breaks after lateral extension. Arthonia epiphyscia, in contrast, develops superficially on the thallus.