Distribution: N - Lig (Brunialti & al. 1999). C - Tosc (Tretiach & Nimis 1994, Putortì & Loppi 1999b, Tretiach & al. 2008, Benesperi 2011), Marc (Nimis & Tretiach 1999), Umb (Ravera 1998, Ravera & al. 2006, Panfili 2007), Laz, Abr (Nimis & Tretiach 1999, Caporale & al. 2016), Mol (Nascimbene & al. 2021), Sar (Loi & al. 2000, Zedda & al. 2001, Zedda 2002). S - Camp (Nimis & Tretiach 2004), Bas (Ravera & al. 2015d), Cal (Puntillo 1995, 1996, Incerti & Nimis 2006), Si (Brackel 2008b, Campisi & al. 2020).
Description: Thallus crustose-subsquamulose, heteromerous, episubstratic, pale grey, blue-grey or brownish grey, of (0.3-)0.5-1(-1.5) mm wide, incised, dispersed to usually contiguous or imbricate areoles/squamules with a whitish margin, developing on a blue-black hypothallus and often forming a cracked crust. Upper cortex sclerenchymatous, 20-30 μm thick, of thick-walled cells. Apothecia lecanorine, 0.3-1 mm across, with a soon convex, orange-brown to red-brown disc, a finally excluded, ple brown proper margin, and an often incompletely developed, granular thalline margin. Proper exciple paraplectenchymatous, 20-40 μm wide; epithecium pale brown; hymenium colourless, 100-140(-180) μm high, I+ blue-green turning reddish; paraphyses simple, coherent, slightly swollen at apex; hypothecium colourless to yellowish, 200-300 μm high. Asci 8-spored, subcylindrical to clavate, with a I+ blue tholus and an internal, more intensely I+ blue structure. Ascospores 1-celled, hyaline, ellipsoid, usually with a single large guttule, apiculate at one or both ends, with a variably thick epispore, 10-14(-16) x (6-)7-9 μm, including the epispore 18-28 x 9-11 μm. Pycnidia wart-like. Conidia bacilliform. Photobiont cyanobacterial (Nostoc, the cells in clusters). Spot tests: thallus K-, C-, KC-, P-, UV-. Chemistry: without lichen substances.
Note: a Mediterranean-Atlantic species, usually found in cracks of the bark of ancient trees, near the base of the boles; mostly Tyrrhenian in Italy.