Distribution: S - Cal (Puntillo 1996, van den Boom & Giralt 2002).
Description: Thallus crustose, inapparent, fully endosubstratic. Apothecia lecideine, black, 0.2-0.4(-0.6) mm across, sessile and constricted at base, with a flat to slightly convex disc and a raised, persistent proper margin. Proper exciple brown in outer part, colourless within, but filled with minute brown crystals dissolving in K, composed of thin anastomosing hyphae with enlarged, brown-pigmented cortical cells; epithecium brown to dark blue-green, N+ red; hymenium colourless; paraphyses lax in K, simple or sparingly branched, stout, 2-3 µm thick at mid-level, the apical cells distinctly capitate, up to 5 µm wide; hypothecium colourless, but filled with minute brown crystals dissolving in K. Asci 8-spored, clavate, with a K/I+ blue apical dome penetrated by a narrow, K/I– apical cushion surrounded by a narrow, deeply K/I+ blue zone, the wall K/I- but surrounded by an I+ red-brown, K/I+ blue outer layer, the ocular chamber relatively small, Biatora-type. Ascospores 1-celled, hyaline, globose, 4-6 µm wide. Photobiont chlorococcoid, the cells 9-12 µm wide. Spot tests: thallus K-, C-, KC-, P-. Chemistry: thallus probably without lichen substances.
Note: a mainly cool-temperate to boreal-montane lichen also known from the Southern Hemisphere, found on hard, exposed lignum, more rarely on conifer bark; to be looked for in the Alps. According to Printzen (1995) the generic position of this species, related to the North American Lecidea paddensis (Tuck.) Zahlbr., is not clear.
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual
Most common in areas with a humid-warm climate (e.g. most of Tyrrenian Italy)