Thallus: foliose, circular in outline or irregularly spreading, up to 10 cm wide, loosely adnate to adnate, irregularly lobate lobes: flat to convex, discrete, loosely imbricate, short linear, 2-5 mm long, mostly 0.5-2 mm wide, tips rounded, entire or weakly crenulate upper surface: pale gray to ash colored (pale brown in herbarium), dull or somewhat shiny, emaculate; pseudocyphellae irregularly rounded to sublinear, up to 0.7 mm long and 0.13 mm wide, isidiate isidia: laminal, cylindrical, simple; soredia absent upper cortex: paraplectenchymatous, 20-30 micrometer thick, composed of 4-5 layers, lumina up to 7 micrometer diam., pale brown medulla: white, 100-110 micrometer thick, often with internal cephalodia lower cortex: c. 20-25 micrometer thick, composed of 3-4 layers, pale brown lower surface: brown to brownish black centrally, densely short (>8 [or 35] micrometer long) tomentose, moderately rhizinate; rhizines: simple, up to 1.2 mm long, pale brown initially and darkening with age Apothecia: rare, laminal, stipitate, up 3 mm diam., margin weakly lobate, often densely isidiate; disc: reddish to blackish brown; epithecium: reddish brown, c. 10 micrometer thick; hymenium: hyaline below, c. 100-120 micrometer thick, I+ blue; subhymenium pale brown, 20-30 micrometer thick; hypothecium colorless, c. 20 micrometer thick; paraphyses: simple, cylindrical, septate asci: obclavate, 8-spored ascospores: acicular, 7-septate at maturity, colorless, 90-105 x 8-9 micrometer Pycnidia: not seen Spot tests: upper surface K+ yellow, C-, KC-, P-; medulla K-, C-, KC+ rose, P- Secondary metabolites: cortex with substance "A"; medulla with gyrophoric acid (major). Habitat and ecology: on bark or rock in very humid microclimates World distribution: Mexico to Brazil, including the West Indies Sonoran distribution: Sierra Madre Occidental region of central Sinaloa. Notes: Lobariella exornata is only tentatively identified for the Sonoran region, although it does occur at the northern end of the Sierra Madre Oriental in Tamaulipas.