Thallus: foliose, 2-7 cm in diam., adnate to loosely adnate, subdichotomously lobate lobes: sublinear, elongate, plane or convex, 2-7 mm wide; margin: entire; apices: subtruncate, plane to convex upper surface: light gray, smooth, shiny, emaculate soredia: in slightly excavated soralia of pustulae that initially may appear dactylate (but not isidia-like as in H. dactylifera); isidia absent medulla: white with continuous algal layer lower surface: black, shiny; rhizines: sparse, black, dichotomous Apothecia: sparse, laminal, substipitate, 1-8 mm in diam.; disc: brown; margin: crenulate, sorediate asci: clavate, 8-spored ascospores: rare, ellipsoid, 11-12 x 6-7 µm Pycnidia: marginal, immersed conidia: not seen Spot tests: upper cortex K+ yellow, C-, KC-, P+ yellow, UV-; medulla K-, C+ red, KC+ red, P- Secondary metabolites: upper cortex with atranorin and chloroatranorin; medulla with lividic acid (major), colensoic, methoxycolensoic, 4-O-methylphysodic acids (all submajor), gyrophoric acids (minor), and physodic, oxyphysodic, norcolensoic and 4-O-methyllividic acids (all trace). Substrate and ecology: on hardwood bark in lower montane to montane forests World distribution: neotropics and southern USA Sonoran distribution: in the mountains of SE Arizona. Notes: In the Sonoran region this species may be confused with the more common H. dactylifera but that species has a different chemosyndrome, in which lividic acid is at most a trace as well as development of dactyls. Also the lobes of H. pustulifera are usually wider than those of H. dactylifera.