Description: Thallus foliose, heteromerous, dorstiventral, broad-lobed, potentially to 30 cm across, loosely attached, without soredia and isidia. Lobes broad and rounded, rarely linear, 1-3(-4) cm wide, more or less dichotomously divided, ascending at tips. Upper surface more or less glossy, grey-green to grey-brown, briwght green when wet, strongly reticulately ridged with marked depressions, lacking isidia and soredia. Lower surface white to pale brown at margins and on the swellings corresponding to the depressions on upper surface, otherwise brown-black, tomentose except on the swellings, erhizinate or with dark, up to 4 mm long rhizines. Upper cortex pseudoparenchymatous, 30-50 µm thick, consisting of 5-6 layers of cells with c. 10 µm wide lumina; medulla white, often with internal cephalodia appearing on the surface as c. 2 mm broad swellings. Apothecia common, laminal or marginal, most frequent on ridges, up to 3.5(-4) mm across, with a brown-red disc and a warted thalline margin. Epithecium reddish brown; hymenium colourless or pale brown in lower part, 95-113 µm high; paraphyses 1.5-2.5 thick, not capitate; hypothecium brownish, 60-110 µm high. Asci (6-)8-spored, clavate, Peltigera-type. Ascospores 1-(3)-septate, fusiform to narrowly ellipsoid, straight, hyaline, 21-34 x 6-9 µm. Pycnidia laminal and marginal. Conidia bacilliform, c. 5 x 1-1.5 µm. Photobiont chlorococcoid. Spot tests: upper cortex K-, C-, KC-, P-, UV-;medulla K- or K+ pale yellow. Chemistry: tenuorin, 4-0-methylgyrophoric and gyrophoric acids, plus traces of other substances.
Note: a circumpolar, arctic-alpine species found on bryophytes and acid soil rich in humus over siliceous substrata near and above treeline: restricted to the Alps in Italy.
Growth form: Foliose, broad lobed
Substrata: soil, terricolous mosses, and plant debris