Description: Thallus crustose, episubstratic, rimose to areolate, with a paraplectenchymatous cortex, 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. Medulla poorly developed, I-. Apothecia lecanorine, sessile, 0.5-1 mm across, with a pale brown to dark red-brown, flat to slightly convex disc and a thick, smooth thalline margin. Amphithecium corticate, paraplectenchymatous, brownish in outer part; proper exciple poorly developed; epithecium brownish; hymenium colourless K+ orange-brown; paraphyses slender, sparingly branched and anastomosing, with subglobose terminal cells; hypothecium colourless or pale brown in lower part. Asci 8-spored, cylindrical-clavate, Porpidia-type. Ascospores 1-celled, hyaline, ellipsoid, 19-35 x 8-17 µm, when young often with a gelatinous sheath, the wall I-. Pycnidia black, immersed at the top of papillae. Conidia bacilliform, 4.5-5 x 1-1.5 µm. Photobiont chlorococcoid. Spot tests: thallus K-, C-, KC-, P-. Chemistry: traces of gyrophoric acid and 5-0-acethyl-4-methylhyascic acid.
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)