Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2002. Lichen Flora of the Greater Sonoran Desert Region. Vol 1.
Thallus: foliose, forming orbicular rosettes, up to 5 mm diam., on fibrous, well-developed hypothallus that sometimes extends as a blue-black zone around the thallus lobes: mostly concave, 3-4 mm wide, up to 8 mm long, with raised, whitish margins that are deeply incised upper surface: bluish gray to fawn-colored (olive-brown), smooth to pruinose or sometimes scabrous at the apices upper cortex: paraplectenchymatous, 40-50 µm thick Apothecia: common, frequently centrally, up to 1.5 mm; disc: red-brown, with a persistent, crenulate thalline margin; exciple: subparaplectenchymatous, 30-40 µm thick; hymenium: primarily hyaline but brown above, partially I+ blue (in vicinity of the asci), 110-150 µm high asci: clavate to subcylindrical, without internal amyloid apical structures, 8-spored ascospores: simple, colorless, broadly ellipsoid, with an epispore, 20-24 x 10-12 µm (with epispore) Pycnidia: not seen Spot tests: thallus K-, C-, KC-, P+ orange Secondary metabolite: pannarin. Substrate and ecology: on bark in cool-temperate forests World distribution: widespead in both Northern and Southern Hemispheres Sonoran distribution: at the upper limit of the oak forests in Sinaloa and Chihuahua, sometimes extending into the conifer forests. Notes: It is mostly confused with P. lurida and P. subfusca. The former species is usually broader and has duller lobes, that are heavily wrinkled when dry. In contrast, P. subfusca is a smaller, thinner, brownish, P- species. The separation from the smaller, often abundantly fertile P. malmei Dodge, which is best recognized by its smaller spores (12-15 x 8-9 µm), is more difficult.