Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.
Thallus: umbilicate-squamulose squamules: initially small and flat, 0.4-0.8 mm wide, with rosulate margin and a few apothecia, later squamules bulging and lobulate, 1-2(-4) mm wide and with numerous apothecia upper surface: black with dark green tinge, dull or slightly glossy, rarely gray pruinose, uneven, warty to lobulate anatomy: apically vertical fan-shaped, mycobiont cells small and elongated, basally with a thick, fairly large-celled paraplectenchymatous layer lacking photobiont cells lower surface: attached by small central umbilicus Apothecia: sessile, finally with slightly constricted base, 0.25-0.4(-0.5) mm wide, usually several per squamule; thalline margin distinct, persisting, smooth or rarely somewhat lobulate disc: dark red, at first punctiform and depressed, later open and slightly sunken proper exciple: thin but distinct, hyaline epihymenium: yellowish brown, K- hymenium: hyaline, up to 125 µm tall, becoming divided by intrusions of bands of sterile hyphae, IKI-; subhymenium: hyaline, IKI+ pale blue ascus: prototunicate, 8-spored ascospores: hyaline, simple, ellipsoid, 10-12.5 x 5.5-7.5 µm, thin-walled Pycnidia: immersed, ±globose, 150-200 µm wide; wall: simple or eventually convoluted conidia: bacilliform, c. 4 x 1-1.5 µm Spot tests: all negative Secondary products: none detected. Substrate and ecology: on acidic rock, usually on N-facing rock surfaces on rocky slopes World distribution: North America Sonoran distribution: Baja California Sur. Notes: Pterygiopsis mutabilis differs from P. atra and P. cava in the squamulose-pulvinate growth form. Leprocollema americanum is somewhat similar but lacks the paraplectenchymatous basal layer and differs in the thick excipulum proprium and the multiply umbonate apothecial disc.