Basionym: Data lacking.
Synonym: Index Fungorum
Type: Data lacking.
Barcode: Data lacking.
Coordinates: Data lacking.
Thallus: foliose, forming small to medium sized rosettes up to 3 cm wide, sometimes coalescing, adnate to loosely adnate, lobate; lobes dorsiventral, flattened to convex, 0.8-2 mm wide; tips: truncate to rotund, 0.3-0.9 mm wide; upper surface yellow to orange, smooth to shiny, sorediate; soredia powdery, marginal in horizontal crescent-shaped slits ('bird nests'); medulla white, reticulate, with short to elongate hyphae; lower surface white to yellow, somewhat wrinkled, rarely with short, white hapters. Apothecia rare, laminal, stipitate, up to 2.5 mm in diam.; margin initially smooth but often becoming sorediate and with cilia; disc orange; epihymenium brown, c. 10 µm thick; hymenium hyaline below, 50-110 µm tall; paraphyses simple or branched, cylindrical, septate; hypothecium hyaline to pale brown, 30-90 µm thick; asci clavate, 8-spored. Ascospores ellipsoid, polarilocular, hyaline, 11.5-17 x 6-9 µm; septum 2-5 µm wide. Pycnidia common, immersed to protruding, darker than upper surface; conidia bacilliform, 2-3.6(-4.5) x 1-1.5 µm (Nash et al. 2001: xx).
Photobiont: Data lacking.
Chemistry: Upper surface K+ purple, C-, KC-, P-; parietin (major), fallacinal (major), emodin, teloschistin (major), parietinic acid (Nash et al. 2001: xx).
Ecology: On bark, rarely rock or detritus, in rather humid to dry, but not very dry microclimates. Molecular data: Genbank
Distribution: Database
Note: In Nash et al. there are the authors "Xanthomendoza fallax (Hepp ex Arn.) Søchting, Kärnefelt & S. Kondratyuk".