Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2002. Lichen Flora of the Greater Sonoran Desert Region. Vol 1.
Thallus: orbicular to irregular, to 5 cm diam., ± closely adnate to the substrate lobes: up to 2 mm wide, mostly c. 1 mm, often imbricate, tips rounded, sometimes with the inner parts dissected into small lobes, eciliate upper surface: whitish gray to gray, usually shiny, sometimes with white dots or a pruina upper cortex: paraplectenchymatous medulla: white lower cortex: paraplectenchymatous, thick, brownish to black cell walls lower surface: black except for pale lobe tips, with black, abundant rhizines Apothecia: usually abundant, up to 2 mm across; disc: dark brown to black, sometimes covered with a white pruina ascospores: brown, 1-septate, Pachysporaria-type, (18.5-) 21-26 (-32.5) x (8.5-) 9-11.5 (-14) µm Pycnidia: abundant Spot tests: cortex and medulla K+ yellow, C-, KC-, P+ yellow Secondary metabolites: upper cortex with atranorin; medulla with atranorin, zeorin, lecotylin and occasionally some unidentified triterpenes. Habitat and ecology: growing on tree trunks and rocks in rather open but moist, subtropical situations World distribution: known from a few scattered areas in East Africa, Mexico and South America Sonoran distribution: only known from one locality near Baseseachic Falls in Chihuahua. Notes: In its appearance this species is close to P. aipolia, but easily separated by its black, distinctly paraplectenchymatous lower cortex and the ± shiny upper surface. In some specimens the thallus is dissected into narrow lobes.