Martinjahnsia resendei (Poelt & Tav.) S Y. Kondr. = Xanthoria resendei Poelt & Tav.

    Thallus tightly attached to the substratum, rosette-forming, 4-8 cm diam., lobate, lobes long, thick, dichotomously branched, markedly convex, worm-like, stiff, surface granulose to verrucose, bright orange to golden yellow, scattered with paler rounded spots. Apothecia common, more or less numerous, cup-shaped at first, then sessile, 1-2 mm diam., disc flat, concolourous, exciple smooth to crenulate, paler, soon excluded. Ascospores broadly ellipsoid, polarilocular, 8-12 x 6-8 µm, septum  3-4.5 µm thick. Photobiont: Trebouxioid, distributed as glomeruli. K+ purple. Coastal, Mediterranean and Macaronesian on nutrient-rich substrata, notably dry vertical walls of slightly acid rocks, highly exposed to to direct sun.

_ This species is close to Xanthoria elegans but differing from it macroscopically by a more robust and larger thallus and microscopically by different characters, but especially by its habitat.

_ Also very close to Xanthoria aureola, but the latter has narrow, indented, strap-shaped lobes.