Distribution: N - Piem, Lig. C - Tosc (Ravera & al. 2020), Sar.
Description: Thallus crustose, episubstratic, up to 0.8 mm thick, smooth, rimose-areolate or verrucose-areolate, often discontinuous, whitish-grey to pale brown. Areoles 0.5-2 mm wide. Apothecia lecanorine, 0.3-0.7(-1) mm across, rounded to irregular in outline by mutual compression, with a dark brown to black (translucent and brown-speckled when wet), flat to slightly convex, epruinose disc, a smooth, finally excluded thalline margin, and often a thin parathecial ring. Thalline exciple ecorticate, the medulla with sparse algal cells; proper exciple thin, poorly developed, of dark-pigmented hyphae; epithecium brown or patchily greenish brown to black, with an epipsamma; hymenium colourless, (60-)70-90 µm high; paraphyses c. 1.5 µm thick, gradually widening to 3-5 µm at apex, difficult to separate due to the abundant hymenial gel; hypothecium colourless or very pale brown. 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 (0-)1(-2)-septate, hyaline, narrowly ellipsoid, (9-)10-13(-16) x 4-5(-6) µm. Pycnidia immersed, reddish-brown around the ostiole. Conidia filiform, curved. Photobiont chlorococcoid. Spot tests: thallus and medulla K-, C-, KC-, P-, UV-. Chemistry: without lichen substances.
Note: a Mediterranean-Atlantic species of siliceous rocks, including basalt, often starting the life-cycle on species of Caloplaca s.lat.; most frequent in Tyrrhenian Italy. The species seems to be mostly coastal in NW Europe; the record from the Alps of Piedmont is somehow dubious.
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)