Description: Thallus fruticose, once or twice dichotomously branched, cream-coloured, smooth and glossy, deep red-purple to violet at the necrotic base, loosely attached, sometimes forming compact mats. Lobes flattened, smooth, canaliculated to subtubular, erect to ascending, 2-4(-8) cm tall, to 5 mm broad (usually less in Italian material), often white-maculate on upper surface, the margin with black, short-spinulose pycnidia; lower surface corticate, with narrow, marginal, whitish pseudocyphellae. Cortex thin, paraplectenchymatous in upper part; medulla white, rather lax. Apothecia extremely rare, zeorine, submarginal at lobe-ends, with a brown disc. Asci 8-spored, narrowly clavate, Lecanora-type. Ascospores 1-celled, hyaline, ellipsoid, 5-10 x 3-5.5 µm. Pycnidia black, immersed in marginal projections. Conidia dumbbell-shaped (thickened at both ends), c. 6 x 1 µm. Photobiont chlorococcoid. Spot tests: cortex K-, C-, KC+ yellowish, P-: medulla K-, C-, KC-, P-; reddish basal parts K+ red. Chemistry: cortex with usnic acid; medulla with lichesterinic and protolichesterinic acids; basal necrotic parts with anthraquinones.
Note: a circumpolar, arctic-alpine lichen, a typical element of tundra-like vegetation in open, dry habitats above treeline, most frequent on basic siliceous substrata, in wind-exposed ridges. The species was neotypified on an Italian specimen (see Thell & Moberg 2011).
Growth form: Fruticose
Substrata: soil, terricolous mosses, and plant debris
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by thallus fragmentation