Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2002. Lichen Flora of the Greater Sonoran Desert Region. Vol 1.

Thallus: foliose, ± firmly appressed, up to 8 cm in diam., usually smaller (3-5 cm) lobes: flat to slightly concave, 0.3-0.6 mm wide soredia: always present, farinose, initially in marginal, fissural, rarely later in laminal, orbicular soralia; isidia and polysidiangia lacking medulla: upper part lemon to beige yellow, very thin lower part white lower surface: black in center, paler towards lobe tips; rhizines: ± dense, blackish, furcately divided Apothecia: obscurascens-type, common, laminal, 0.3-1.5 mm wide; disc: black, not pruinose internal stipe: weakly developed, upper part brownish-red, lower part whitish ascospores: one-septate, brown, 13-19 x 6-8 µm Pycnidia: immersed conidia: bacilliform, 3-4 x 1 µm Spot tests: upper cortex K-, C-, KC-, P-; medulla upper and lower part K-, C-, KC-, P-; internal stipe upper part K+ purple, C-, KC-, P-; lower part K-, C-, KC-, P- Secondary metabolites: upper cortex with lichexanthone; medulla with terpenes of a characteristic pattern on TLC plates, and an unknown pigment. Substrate and ecology: on bark, wood, and rarely on acidic rocks from sea level to high montane areas World distribution: pantropical with scattered collections from the subtropics and warm temperate regions, insular Laurimacaronesia and Europe/Italy Sonoran distribution: Arizona, Baja California Sur, Sinaloa and Sonora, at low to intermediate elevations from thorn forests to oak forests. Notes: Previously specimens belonging to this species have been reported under the names of P. caesiopruinosa and P. meissneriana.