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DescriptionLife habit: lichenized; Thallus: foliose to subfruticose, circular in outline, often forming rosettes or irregularly coalescing and spreading extensively over its substrate, loosely adnate to adnate, lobate; lobes: usually flattened to convex or concave but sometimes subterete, discrete, often loosely imbricate, elongate, horizontal with tips sometimes ascending or semi-erect to erect, eciliate; upper surface: mostly some shade of orange but in shade paling to yellow, occasionally pale green to gray, dull or somewhat shiny, with or without pruina, lacking pseudocyphellae, with or without isidia or soredia; upper cortex: paraplectenchymatous; medulla: white, with or without hyphae bundles, or lax and reticulate; primary photobiont a Trebouxia sp., secondary photobiont lacking; lower cortex: paraplectenchymatous; lower surface: white to yellow, smooth to somewhat wrinkled, with or without simple hapters; Ascomata: present or absent, apothecial, zeorine, laminal, sessile to stipitate; margin: concolorous with the thallus, smooth or sorediate; disc: darker orange than the thallus, sometimes pruinose, eperforate; epihymenium: bright yellowish orange; hymenium: usually hyaline below but light orange above, sometimes with oil droplets; hypothecium: hyaline to pale brown; paraphyses: simple or branched, sometimes anastomosing below; asci: clavate to broadly clavate, 8-spored, Teloschistes-type (sensu Honegger 1978); ascospores: ellipsoid to narrowly ellipsoid, polarilocular, hyaline, 10-20 x 4-10 µm; septum: narrow to wide, 1-8 µm; Conidiomata: pycnidial, concolorous with the thallus or darker, immersed or protruding; conidia: simple, ellipsoid, hyaline; Secondary metabolites: anthraquinones present in colored parts; Geography: worldwide; Substrate: bark and rock, rarely on detritus or other substrates.; Notes: Morphologically and chemically Xanthoria is similar to Xanthomendoza, but Xanthoria differs mainly by having ellipsoid conidia, and hapters instead of well developed rhizines (see also Søchting et al. 2002). The taxonomy of Xanthoria in relation to the genera Caloplaca and Teloschistes is currently unresolved.