Thallus: orbicular to irregular, up to 5 cm in diam. lobes: up to 2 mm wide, usually broadest near the tips, usually overlapping, eciliate upper surface: whitish gray to gray, shiny or rarely pruinose, ± distinctly white maculate (c. like P. aipolia), sorediate soredia: often granular, in marginal, small and delimited soralia that occasionally becomed capitate upper cortex: paraplectenchymatous medulla: white lower cortex: paraplectenchymatous lower surface: black, with dark gray lobe tips; rhizines: black Apothecia: not seen in the Sonoran material, but elsewhere not common, up to 2 mm diam.; margin: crenulated and sometimes disintegrating into soredia; disc: black, with or without pruina ascospores: brown, 1-septate, Pachysporaria type, 20-26 x 9-11 µm Pycnidia: not common Spot tests: cortex and medulla K+ yellow, C-, KC-, P+ yellow Secondary metabolites: upper cortex with atranorin; medulla with atranorin and zeorin. Substrate and ecology: growing both on rocks or on tree trunks in open situation World distribution: known from South America and East Africa and southeastern Asia Sonoran distribution: not known from the Sonoran Desert proper but may be present as it is recorded from Mexico east of the study area. Notes: The species is closely related and similar to P. erumpens as was discussed under that species.