Description: Thallus subfoliose to subfruticose, loosely attached, often forming large tufts, consisting of dorsiventral, flattened, elongate, ascending, 1-3(- 4) cm broad and up to 6(-10) cm tall, often sparingly branched laciniae with often in-rolled margins bearing short (0.2-1 mm) marginal, pycnidia-bearing spinulose outgrowths. Upper surface dark brown in sun-forms to pale olive-green in shade, matt or somehow glossy, smooth or often slightly wrinked, the basal parts often reddish; lower surface usually paler, with large, maculiform, irregular, white pseudocyphellae spread throughout the surface and the margins. Cortex 2-layered, with an external layer of brownish, thick-walled, paraplectenchymatous cells, and an inner layer of periclinally arranged hyphae; medulla white. Apothecia extremely rare, lecanorine, mostly subterminal, with a dark brown disc and an often crenulate thalline margin. Epithecium brownish; hymenium and hypothecium colourless. Asci 8-spored, Lecanora-type. Ascospores 1-celled, hyaline, ellipsoid to ovoid, 6-10 x 3.5-5 μm. Pycnidia immersed at the top of the marginal spinules, often empty. Conidia fusiform, multiseptate, colourless, 6-7 x c. 1 μm. Photobiont chlorococcoid. Spot tests: cortex K-, C-, KC-, P-; medulla K- or K+ yellow-orange, C-, KC-, P+ yellow to orange or P-, UV-. Chemistry: medulla with fumarprotocetraric acid, and variable amounts of protocetraric and protolichesterinic acids.
Note: an arctic-alpine to boreal-montane, circumpolar lichen found on mineral and organic soil, amongst thick moss carpets, exceptionally on bark or lignum near the ground, with optimum near treeline; common and often abundant throughout the Alps, less frequent in the mountains of southern Italy. The subsp. crispiformis (Räsänen) Kärnefelt should be looked for in the Alps.
Growth form: Fruticose
Substrata: soil, terricolous mosses, and plant debris
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by thallus fragmentation