Arthonia protoparmeliopsidis  

Thallus: absent.
Anamorph: not known.
Teleomorph: ascomata 0.1–1 mm diam., often in small groups, blackish, flat or slightly convex, ± round or rarely irregular in shape, immersed in the apothecial disc or sometimes the thallus of the host lichen, often filling the entire apothecium. Exciple poorly developed. Hymenium 40-50 μm tall, colourless or pale brown, I+ red, K/I+ blue. Epihymenium brownish to olivaceous brown, intracellular pigment not granulose, K– or K+ more intense olivaceous green, N–, covered by a colourless gelatinous sheet 2-8 μm thick. Subhymenium and hypothecium well-developed, to more than 100 μm tall, colourless, I+ blue, K/I+ blue. Interascal tissue of branched and anastomosed paraphyses with short and wide cells, erect, septate, capitate (to 3–5 μm thick) at the apex, brownish to olivaceous green in the upper 3–9(–15) μm. Asci 22–42 × 10–15 μm, broadly clavate to elongate ellipsoidal, the wall strongly thickened in the upper part with a long ocular chamber, hemiamyloid ring present, but often poorly visible, (5–) 8-spored. Ascospores 10–14.5(–15) × (3.5–)4–5.5(–6.5) μm, ellipsoidal, colourless, thin-walled, (1–)2- or 3-septate, not or slightly constricted at the septa, I–, KI–, uniseptate ascospores with a median to submedian septum, perispore absent or very thin.