Distribution: N - TAA (Nascimbene 2005, Nascimbene & al. 2006e), Lomb (Abramini & al. 2008). C - Tosc, Marc (Nimis & Tretiach 1999).
Description: Thallus crustose, episubstratic, of convex to subglobose, greenish white to whitish grey, usually epruinose, corticate areoles. Apothecia micareoid, 0.1-0.3 mm across, sometimes confluent into tuberculate, to 0.8 µm wide aggregates, with a dark brown to brown-black, strongly convex to hemispherical disc, without a distinct proper margin. Proper exciple indistinct; epithecium dark brown, the pigment dissolving in K, sometimes K+ faintly violet; hymenium colourless or with brownish vertical streaks, 30-40 µm high; paraphyses numerous, sparingly branched especially in upper part, 0.8-1 µm thick at mid-level, the apical cells to 2 µm wide; hypothecium pale yellowish brown, K-, N-. Asci 8-spored, cylindrical-clavate, the I+ blue tholus with a wide, I+ dark blue tube structure that expands towards the top, without a pale axial body. Ascospores 0-1(-3)-septate, hyaline, fusiform to ovoid-oblong, sometimes slightly curved, (9-)11-15(-24) x 2-3.5 µm. Pycnidia frequent, immersed to emergent, grey-brown, often paler around the ostiole, the wall pale olivaceous brown, K+ violet. Mesoconidia cylindrical or slightly wider at one end, 3.5-4.5 µm long; microconidia narrowly cylindrical, 4-6.5 µm long. Photobiont micareoid, the cells 4-7 μm wide. Spot tests: K-, C-, KC-, P-, UV-. Chemistry: without lichen substances.
Note: a temperate to circumboreal-montane species with optimum on lignum, more rarely on acid bark, most frequent in Castanea-forests, often with Chaenotheca ferruginea; probably more widespread than the few Italian records would suggest (Alps, Central Italy), but much overlooked.