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DescriptionThallus: foliose, forming small to rather large rosettes up to 3.5 cm wide or small colonies, tightly adnate, lobate; lobes: dorsiventral, flattened to convex, 0.4-1.1 mm wide; tips: 0.3-0.7 mm wide, rotund to truncate; upper surface: yellow to bright orange, somewhat coarse, sorediate; soredia: granular, coarse, formed by small, spherical, laminal pustule-like isidia breaking up into soralia; medulla: white, bundled, with elongate hyphae; lower surface: white, smooth or somewhat wrinkled, with extremely short, white hapters; Apothecia: very rare, laminal, stipitate, up to 2 mm in diam.; margin: smooth to crenulate; disc: orange; epihymenium: brown, c. 10 µm thick; hymenium: hyaline below, 60-90 µm tall; hypothecium: hyaline to pale brown, 20-50 µm thick; paraphyses: simple or often branched, cylindrical, septate; asci: clavate, 8-spored; ascospores: ellipsoid, polarilocular, hyaline, 12-14 x 6-8.5 µm; septum: 3-4 µm wide; Pycnidia: common, immersed among soralia, slightly darker than the upper surface; conidia: ellipsoid, 2.2-3.3 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, often calciferous sandstones and exposed, nutrient rich surfaces, in rather dry microclimates at high altitudes; World distribution: circumpolar and boreal extending farther south in montane regions, also in subantarctic regions and Australasia; Sonoran distribution: rare in the mountains of Arizona, southern California, and Baja California.; Notes: Xanthoria sorediata is similar to X. elegans, but X. sorediata invariably produces soralia on the upper surface.