Distribution: N - Ven (Thor & Nascimbene 2007), Lomb (UPS-L166832). S - Camp (CLU 17865), Cal (Puntillo 1996, 2000).
Description: Thallus crustose, thin, ecorticate, continuous, rimose or warted, grey-green, smooth to granulose, usually not producing goniocysts. Apothecia biatorine, usually numerous, 0.15-0.25 mm across, whitish, pale yellow or pale grey, with a flat to slightly convex, epruinose disc, and a usually paler, white or very pale yellow, persistent proper margin. Proper exciple 4–6 cells thick, laterally 24-33 μm wide, without crystals, of very thin-walled (0.5-1 μm), not distinctly radiating hyphae, the outer rim colourless or very pale brown in uppermost part, the medullary part colourless. Epithecium colourless or rarely very pale brown and in this case K+ purple, indistinctly delimited from the hymenium; hymenium 30-40(-50) μm high, mostly colourless; paraphyses mostly simple, 1.5-2 μm thick at mid-level, the apical cells clavate or only slightly thickened, to 3-4(-6) μm wide; hypothecium poorly developed, colourless. Asci 8-spored, clavate to cylindrical-clavate, the apical dome K/I+ dark blue with a pale, conical-pointed apical cushion (axial mass) never penetrating through the entire d-layer, the wall K/I-, but the thin outer gel K/I+ blue, Bacidia-type. Ascospores (0-)1-3-septate, hyaline, needle-like, straight to sigmoid, twisted in the asci, (17-)21-34(-39) x 0.9-1.8 μm. Pycnidia immersed, colourless. Macroconidia filiform, curved and non-septate, microconidia lageniform, 3.0–4.0 × 1.0–1.5 µm. Photobiont chlorococcoid, the cells 5-12(-14) μm wide. Spot tests: thallus and apothecia K-, C-, KC-, P-, UV-. Chemistry: thallus without lichen substances.
Note: a mainly temperate to southern boreal species found on tree stumps, rotten woodwork, rusted iron, plant remnants, ground-cover plastic, rubber waste, coniferous twigs and needles, twigs of Vaccinium myrtillus, decaying vascular plant remnants, moribund bryophytes, pebbles and boulders of siliceous rock, mostly near the ground (Ekman 2023); certainly overlooked, and perhaps more widespread in Italy below the alpine belt, including in the Alps.
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual
Most common in areas with a humid-warm climate (e.g. most of Tyrrenian Italy)