Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.
Thallus: crustose, areolate with distinctly effigurate margin areoles: usually angular, plane or slightly convex, central areoles 0.2-0.5(-0.6) mm wide, marginal areoles usually distinctly elongated, 0.35-0.8 x 0.15-0.25 mm high upper surface: black, smooth anatomy: paraplectenchymatous, distinctly vertical fan-shaped lower surface: usually attached by gelatinous basal layer Apothecia: sessile, 1 per areole, 0.2-0.35 mm wide; margin: distinctly thalline persisting, smooth disc: blackish brown, at first punctiform and depressed, finally open and ±plane proper exciple: thin but distinct, hyaline or apically slightly yellowish brown epihymenium: yellowish brown, K- hymenium: hyaline or faintly red, 90-110 µm tall, IKI- (according to Vainio's diagnosis bluish); paraphyses: tips moniliform; hypothecium: hyaline or ±pale brown, IKI- ascus: prototunicate, 8-spored ascospores: hyaline, simple, broad ellipsoid to subglobose, 8-12.5 x 6-7 µm, thin-walled Pycnidia: laminal, immersed to sessile, c. 0.1 mm wide; wall: finally convoluted conidia: subglobose to cylindrical, 2-5 x 1-1.5 µm, acrogenous Spot tests: all negative Secondary products: none detected. Substrate and ecology: usually on acidic rock along seepage tracks World distribution: Brazil, North America Sonoran distribution: a single report from Baja California Sur. Notes: Pterygiopsis atra differs from P. cava and P. mutabilis in the areolate-crustose growth form with distinctly elongated marginal areoles. According to Henssen (1968) Pterygiopsis atra occurs in western North America together with Lichinella americana, a widespread Sonoran Desert species. No locality data were provided and the material was not available for study. However, Pterygiopsis atra was recently reported from NW Texas (Schultz 2006).