Description: Thallus crustose, mostly endosubstratic, rarely thinly epiosubstratic, up to 40 μm thick, not well-delimited, greenish grey to olive-coloured, the hyphae K/I-. Apothecia arthonioid, rounded, red-brown to brown-black, 0.2-1(-1.5) mm across, 50-75 μm tall, with a flat to slightly convex disc, without a distinct proper margin. Epithecium indistinct; hymenium 25-35(-40) μm high, orange-brown, K+ pale purple, I+ wine-red; paraphysoids 0.5-1(-1.5) μm thick, not swollen ar apices, without a dark cap; hypothecium orange-brown, 30-40 μm high. Asci 8-spored, broadly clavate to subglobose, distinctly stipitate, semi-fissitunicate, with a large apical dome and a distinct ocular chamber, Arthonia-type. Ascospores 1-septate with slightly unequal cells, hyaline, ovoid, 7-11 x 3-4 μm. Pycnidia frequent, brown, the wall orange- to red-brown, K+ pale purple, the pigments not dissolving. Conidia bacilliform or narrowly ellipsoid, straight or slightly curved, 3-6 x 0.5-1 μm. Photobiont trentepohlioid. Spot tests: thallus K-, C-, KC-, P-. Chemistry: thallus without lichen substances.
Note: a mainly temperate lichen found on smooth bark in humid forests (e.g. on Ilex in the southern mountains), but also on basal parts of old oaks inside humid forests. The species is included in the Italian red list of epiphytic lichens as “Near-threatened” (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)