Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.
Thallus: dwarf-fruticose, forming small, irregular cushions, 1.5-5 mm wide lobes: 0.2-0.6 mm wide, 1(-2) mm long, c. 0.15 mm thick, up to 0.5 mm thick when becoming hollow and inflated, cylindrical to slightly flattened or somewhat knotty upper surface: blackish with dark reddish tinge, rarely somewhat grayish pruinose, smooth anatomy: small-celled paraplectenchymatous, becoming hollow and internally corticate against the central cavity lower surface: attached by small gelatinous holdfast Apothecia: sessile, eventually stipitate, 0.35-0.55 mm wide; margin: distinctly thalline, persisting and smooth, disc: reddish to yellowish brown, at first slightly punctiform and depressed, finally open and ±plane proper exciple: thin but distinct, hyaline epihymenium: pale yellowish brown, K- hymenium: hyaline, 125-150 µm tall, finally divided by intrusions of 1-2 bands of sterile hyphae, IKI+ blue; subhymenium: hyaline, IKI+ blue asci: prototunicate, 24-32-spored ascospores: hyaline, simple, globose to subglobose, 4-6 x 4-5 µm, thin-walled Pycnidia: immersed to slightly elevated, globose to broadly pyriform, 150 x 125 µm, wall simple conidia: bacilliform, 3-4 x c. 1 µm Spot tests: all negative Secondary products: none detected. Substrate and ecology: on acidic rock, on inclined rock surfaces and seepage tracks World distribution: North America Sonoran distribution: central and southeastern Arizona. Notes: Pterygiopsis cava is distinguished from other dwarf-fruticose cyanobacterial lichens in the Sonoran Desert region by the hollow, internally corticated lobes, the polysporous asci and small, globose ascospores.