Description: Thallus crustose, episubstratic, rimose to areolate, often delimited by a dark prothallus, with numerous, whitish grey to pinkish grey, isidia-like, cylindrical to subclavate, 0.5-1.2 mm tall papillae bearing a pycnidium on the top. Cortex paraplectenchymatous, brownish in uppermost part, without a distinct epinecral layer; medulla poorly developed, I-. Apothecia lecanorine, sessile, sometimes slightly constricted at base, 0.5-1(-1.2) mm across, with a pale brown to dark red-brown, flat to slightly convex disc and a thick, smooth thalline margin. Thalline exciple corticate, paraplectenchymatous, brownish in outer part; proper exciple poorly developed; epithecium brownish, with coarse granules dissolving in N; hymenium colourless, 125-180 µm high, K+ orange-brown; paraphyses coherent, slender, sparingly branched and anastomosing, with subglobose terminal cells; hypothecium colourless or pale brown in lower part. Asci 8-spored, elongate-clavate, with a thin, outer amyloid layer and a thickened tholus penetrated by a pore, the sides of which stain I/KI+ deep blue, Porpidia-type. Ascospores 1-celled, hyaline, ellipsoid, 19-30(-35) x 8-13(-17) µm, when young often with a gelatinous sheath, the wall thin, I-. Pycnidia black, immersed at the top of the papillae. Conidia bacilliform, (3.5-)4.5-5 x 1-1.5 µm, often with a short attachment peg at one end. Photobiont chlorococcoid. Spot tests: thallus K-, C-, KC-, P-. Chemistry: traces of gyrophoric acid and 5-0-acethyl-4-methylhyascic acid, and of an unidentified substance.
Note: an arctic-alpine, circumpolar species found on periodically wetted, base rich siliceous rocks, with optimum near and above treeline; being often sterile, it might have been largely overlooked in the Alps.
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by isidia, or isidia-like structures (e.g. schizidia)