Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.

Thallus: foliose but appearing areolate centrally, very tightly adnate to tightly adnate, 2-4 cm in diam., irregularly lobate lobes: sublinear, short, plane to subconvex, separate and contiguous to subimbricate, 0.2-0.5 mm wide, not lobulate; apices: subtruncate, brown rimmed, smooth to crenate, eciliate upper surface: dark yellow-green to at least partially brown, smooth to rugulose and becoming transversely cracked with age, shiny, epruinose and emaculate, moderately sorediate soredia: farinose, in orbicular, capitate soralia (0.5-1 mm in diam.); isidia and pustulae absent medulla: white, with continuous algal layer lower surface: black, plane, shiny, sparsely to moderately rhizinate; rhizines: dark brown to black, simple, 0.1-0.2 mm long Apothecia: very rare (not seen in Sonoran material), adnate, 1-1.5 mm wide, laminal on thallus; disc: cinnamon-brown to dark brown; margin: smooth, pruina absent asci: clavate, 8-spored ascospores: hyaline, simple, broadly ellipsoid, 8-10 x 5-6 µm Pycnidia: rare, sunken conidia: bifusiform, 5-6 x 1 µm Spot tests: upper cortex K+yellow to orange, C-, KC-, P+ orange; medulla K+ yellow becoming dark red, C-, KC-, P+ orange Secondary metabolites: upper cortex with usnic acid (major); medulla with stictic acid (major), constictic and norstictic acids (both minor), and cryptostictic and peristictic acids (both trace). Substrate and ecology: usually on acidic rocks and rarely on tree bases, often in open habitats World distribution: pantemperate to subarctic in Europe, Asia, southern Africa and western North America Sonoran distribution: occasionally at intermediate elevations in southern California in the coastal mountains. Notes: The rare X. mougeotii is the only sorediate Xanthoparmelia in the Sonoran region and appears to be restricted to habitats with maritime influence, although it is a temperate to arctic/alpine species elsewhere. Sorediate species are more common in southern South America (Nash et al. 1995) and secondarily in Australasia (Elix et al. 1986).