Thallus: foliose, adnate, 4-20 cm in diam., irregularly lobate lobes: subirregular, elongate, plane to subconvex, separate and contiguous, 0.8-3 mm wide, not lobulate; apices: subrotund, smooth to crenate, eciliate upper surface: yellow to yellow-green, smooth but becoming strongly rugose with age, dull to slightly shiny, epruinose and emaculate, without soralia, isidia, or pustulae medulla: white, with continuous algal layer lower surface: pale to medium brown, plane, moderately rhizinate; rhizines: brown, simple, 0.2-0.4 mm long Apothecia: common, substipitate, 2-5 mm wide, laminal on thallus; disc: cinnamon-brown to dark brown; margin: smooth, pruina absent asci: clavate, 8-spored ascospores: hyaline, simple, ellipsoid, 9-12 x 6-7 µm Pycnidia: common, immersed conidia: bifusiform, 6-7 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) and consalazinic acid (minor) and often with norstictic and protocetraric acids (both trace). Substrate and ecology: on acidic rocks, often in open or partially shaded habitats World distribution: Australasia, southern Africa and North and South America Sonoran distribution: very common at intermediate to lower elevations throughout the region. Notes: Xanthoparmelia lineola is one of the most common Xanthoparmeliae in the Sonoran region, extending from the deserts (north-facing slopes) to intermediate elevations in the mountains as well as coastal habitats where it can occasionally be found growing over consolidated soil. In arid habitats where wind blown dust becomes impregnated in tree bases, X. lineola may also be found. Although interpreted as a somewhat narrow-lobed species in Australasia (Elix et al. 1986), it is often quite robust in the Sonoran region.