Description: Thallus crustose, endosubstratic, poorly evident, yellowish white, often delimited by a black prothallus. Apothecia lirelliform, black, epruinose, 0.3-1 x 0.1-0.2 mm, simple or weakly dichotomously branched, laterally anastomosing, straight to curved, prominent, aggregated into 2-3 mm wide, stellate to irregular clusters of 10-20 apothecia. Proper exciple dark brown to black, extending below the hymenium, brittle, the external layer of cells c. 2-3 µm wide, with strongly occluded lumina; epithecium brown; hymenium colourless, I- or I+ yellowish; paraphysoids highly branched and densely anastomosing, c. 2 µm thick; hypothecium dark. Asci 8-spored, clavate, bitunicate, with an evident ocular chamber, K/I- (but cytoplasm usually yellowish brown). Ascospores 1-septate, slightly constricted at septum, one cell slightly shorter and wider than the other, at first hyaline then pale brown, 12-16 x 4-6 µm, with a very thin perispore, the wall ornamented. Pycnidia frequent, half to totally immersed, carbonaceous in upper part, colourless in lower part, producing either macro- or microconidia. Macroconidia simple, ellipsoid, 7-11 x 3-5 µm; microconidia narrowly ellipsoid to bacilliform, 4-8 x 1-2.5 µm. Photobiont trentepohlioid. Spot tests: K-, C-, KC-, P-, UV-. Chemistry: without lichen substances.
Note: a mild-temperate lichen found on compact calcareous rocks in shaded, microclimatically stable situations, often in underhangs; the species seems to be most frequent in Tyrrhenian Italy. For further details see Tretiach & Modenesi (1999).
Growth form: Crustose
Reproductive strategy: mainly sexual
Most common in areas with a humid-warm climate (e.g. most of Tyrrenian Italy)