Thallus: foliose, irregular, sometimes orbicular, to 3 cm. diam., firmly adnate, repeatedly irregularly lobate lobes: radiating, up to 1.5 mm broad, adnate to the tips, ± sinuous, short and overlapping or discrete, flat to convex, minutely notched, eciliate upper surface: whitish gray to gray, mostly distinctly pruinose particularly at lobe-tips; isidiate isidia: marginal and/or laminal, very variable in length from the usual 0.1 mm and knob-like but also rarely up to 0.5 cm long and then becoming lobulate; soredia: sometimes present and may develop from broken isidia or wartlike projections upper cortex: prosoplectenchymatous medulla: white, lax lower cortex: prosoplectenchymatous lower surface: white or pale to medium brown; rhizines: simple, gray to brown Apothecia: ± common, short stipitate, up to 3 mm diam.; margin: scabrous, minutely crenate, isidiose or lobulate; disc: dark brown, epruinose asci: subclavate to clavate, 8-spored ascospores: brown, l-septate, ellipsoid, Pachysporaria-type, without sporoblastidia, (20.5-) 21-27 (-30) x (8.5-) 10.5-14 µm Pycnidia: ± common, inserted in the thallus, visible only as black warts on the surface conidia: bacilliform, 4-5 x 1 µm Spot tests: cortex K+ yellow, C-, KC-, P+ yellow; medulla K+ yellow to red, C-, KC-, P+ orange Secondary metabolites: cortex with atranorin and chloroatranorin; medulla with atranorin, zeorin and salazinic acid (major). Substrate and ecology: mainly growing on bark of various deciduous trees in moist, but open conditions from the thorn forest into adjacent montane areas World distribution: both eastern and SW North America (including Mexico) Sonoran distribution: relatively common in mesquite, riparian areas, thorn forests and deciduous forests at low to intermediate elevations in southern Arizona, Sonora, Sinaloa and Baja California Sur. Notes: Heterodermia granulifera is recognized by the isidia on the lobe margins and/or the upper surface which sometimes develop soralia in the openings after the isidia are broken.