Description: Thallus crustose, not lichenized, infecting the thalli of Pertusaria-species, visible as a darkening of the host thallus. Apothecia sessile, 0.25-0.6 mm across, 0.2-0.3 mm high, usually epruinose (young apothecia rarely white-pruinose at margins), with a black mazaedium. Exciple dark brown, 50-90 µm thick laterally, of strongly sclerotized, interwoven hyphae, with an outer, 2-3 µm thick gelatinous layer, strongly thickened at base and often forming a stalk penetrating the thallus of the host; hypothecium dark brown, 40-55 µm high, of periclinally arranged, sclerotized hyphae. Asci narrowly clavate, formed singly from hooked ascogenous hyphae, persisting until the spores are nearly ripe, with biseriately arranged spores. Ascospores 1-septate and constricted at septum, brown, broadly ellipsoid, 10-15 x 6-9 µm, with a coarse ornamentation of mainly spirally arranged ridges in young spores, later disrupted by a few irregular cracks, the surface appearing striated. Photobiont absent. Spot tests: all negative. Chemistry: without lichen substances.
Note: a species with a grey thallus forming insular patches on the thalli of epiphytic Pertusaria-species (especially P. pertusa, P. coccodes and P. coronata), found on very old oaks; also known from North America, it is most common in western Europe: records from the Alps have a fairly different ecology and conspecifity is therefore in need of confirmation.
Growth form: Lichenicolous fungus
Reproductive strategy: mainly sexual
Most common in areas with a humid-warm climate (e.g. most of Tyrrenian Italy)