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DescriptionThallus: foliose, adnate, 3-10 cm in diam., irregularly lobate; lobes: subirregular, somewhat elongate, plane to subconvex, separate, contiguous to +imbricate, (1-)1.53(-4) mm wide, not lobulate; apices: subrotund, smooth to crenate, eciliate; upper surface: yellow-green, smooth, shiny, epruinose and emaculate, moderately to densely isidiate; isidia: abundant, initially globose, sometimes becoming barrel-shaped to irregularly inflated, 0.1-0.25 mm in diam., 0.1-0.3 mm tall; tips: epicorticate, dull brown, becoming erumpent but not sorediate; soralia and pustulae absent; medulla: white, with continuous algal layer; lower surface: black, plane, moderately to densely rhizinate; rhizines: black, simple, 0.2-0.6 mm long; Apothecia: rare, substipitate, 2-10 mm wide, laminal on thallus; disc: cinnamon-brown to dark brown; margin: smooth, pruina absent; asci: clavate, 8-spored; ascospores: hyaline, simple, ellipsoid, 9-10 x 5-6 µm; Pycnidia: rare, immersed; conidia: bifusiform, 5-6 x 1 µm; Spot tests: upper cortex K-, C-, KC-, P-; medulla K+ yellow becoming dark red, C-, KC-, P+ red; Secondary metabolites: upper cortex with usnic acid (major); medulla with salazinic acid (major) consalazinic acid (minor) and often with norstictic and protocetraric acids (in trace amounts).; Substrate and ecology: on acidic rocks, rarely on wood, usually in open, arid to semi-arid habitats; World distribution: Europe, northern Africa and southwestern North America; Sonoran distribution: common at lower elevations in Arizona, Chihuahua, Sonora, Sinaloa, Baja California and Baja California Sur.; Notes: Provisionally Hale identified the North American salazinic acid-containing, isidiate Xanthoparmeliae with a black lower surface as X. tinctina, but in his 1990 monograph restricted that species to Europe and north Africa based in part on the observation that it is rarely erumpent. North American material was subsequently treated as X. australasica D. Galloway. However, a re-examination of the material does not support that conclusion. Xanthoparmelia australasica is a very broad lobed and loosely adnate species, such that it is usually collected without its substrate. In contrast, the North American material has lobe width equal to or smaller than X. australasica and is typically quite adnate. These characteristics match the European material of X. tinctina. In addition, the isidia of European material are often erumpent in the sourthern part of its range; thus its isidia match those of the North American population whereas the isidia of X. austrasica are thinner, taller and never erumpent.