Distribution: N - Ven, Piem, Lig (Giordani & Brunialti 2000). C - Tosc (Brunialti & Frati 2010, Brunialti & al. 2012b), Laz (Stofer 2006), Sar (Stofer 2006). S - Pugl (Nimis & Tretiach 1999), Cal (Puntillo 1996), Si (CLU 12717).
Description: Thallus crustose, continuous to slightly cracked, thin, mostly episubstratic, white to grey-white. Apothecia lecideine, black, adnate to sessile, round to often irregular in outline (often oval or sublobulate) 0.2-0.7 mm across, with a black, at first flat then convex, uneven, epruinose disc and a thin, finally excluded proper margin. Proper exciple laterally well-developed, dark red-brown, closed below the hymenium, I+ reddish, K/I+ deep blue, K+ blackish olive; epithecium dark brown; hymenium colourless, I+ pale red or blue in the inner part, K/I+ pale blue; paraphysoids richly anastomosing, not thickened at apex, richly branched at apex to form a reticulate epithecium; subhymenium pale to dark brown; hypothecium dark red-brown. Asci 8-spored, narrowly clavate, fissitunicate, the apex with a narrow amyloid apical dome penetrated by a small ocular chamber. Ascospores transversely multi-septate, hyaline, at first filiform and 70-77 x (1-)2-3 µm, but later fragmenting into individual, rectangular to cuboid part-spores which are (2-)3-8 x 2-3 µm. Pycnidia immersed or semi-immersed, punctiform, globose or subglobose, the wall brown at apex, colourless to pale brown basally. Conidia straight, 3-5 x 1-1.5 µm. Photobiont trentepohlioid. Spot tests: K-, C-, KC-, P-. Chemistry: without lichen substances.
Note: a mild-temperate to Mediterranean-Atlantic species found on bark of old, isolated deciduous trees, especially oaks, on faces which are seldom wetted by rain; mainly Tyrrhenian, perhaps exctinct in the plains of the North, and certainly declining. It is included in the Italian red list of epiphytic lichens as “Vulnerable” (Nascimbene & al. 2013c).
Growth form: Crustose
Reproductive strategy: mainly sexual
Most common in areas with a humid-warm climate (e.g. most of Tyrrenian Italy)