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DescriptionThallus: foliose to subfruticose, forming small cushions up to 3 cm wide or extensive colonies, loosely adnate to ascending, attached by central umbilicus-like structure, lobate; lobes: dorsiventral, flattened to convex, 0.1-0.5 mm wide, ±involute; tips: truncate, often involute, 0.3-0.7(-1) mm wide; upper surface: yellow to light orange, smooth to somewhat coarse, often wrinkled, sorediate; soredia: granular, blastidious, in marginal to submarginal soralia or at lobe tips; upper cortex: paraplectenchymatous; medulla: white, reticulate, with short to elongate hyphae; lower cortex: prosoplechtenchymatous; lower surface: white to yellow, somewhat wrinkled, rarely with short, white hapters; Apothecia: rare, laminal or appearing terminal, stipitate, up to 4 mm in diam.; margin: smooth but often sorediate or lobulate; disc: orange; epihymenium: brown, c. 10 µm thick; hymenium: hyaline below, 60-90 µm tall; paraphyses: simple, cylindrical, septate; hypothecium: hyaline to pale brown, 25-70 µm thick; asci: clavate, 8-spored; ascospores: ellipsoid, polarilocular, hyaline, 12-15 x 5.5-8 µm; septum: 3-6 µm wide; Pycnidia: common, immersed, concolorous with upper surface or slightly darker; conidia: ellipsoid, 3.8-5.8 x 1-1.5 µm; Spot tests: upper surface K+ purple, C-, KC-, P-; Secondary metabolites: parietin (major), fallacinal, emodin, teloschistin and parietinic acid.; Habitat and ecology: on rock; World distribution: North America and South America; Sonoran distribution: rare, southern California (Los Angeles Co.).; Notes: Characters in the apothecium of Xanthomendoza mendozae are based on descriptions of South American material (Kondratyuk and Kärnefelt 1997), because X. mendozae has never been observed with apothecia in material from the Sonoran region, or elsewhere in North America.