in Hafellner & Grube, Lichenologist, 55: 245, 2023.
Distribution: N - TAA (Hafellner & Grube 2023).
Description: Thallus not lichenized, lichenicolous on species of the Lecanora polytropa-complex, the infections not distinctly parasitic except in well-defined areas on the host apothecia. Apothecia arthonioid, pure black (somewhat paler at the margins), 0.2-0.6(-1) mm across, rounded, immarginate, developing on the yellowish green discs of the host apothecia, remaining individual or rarely 2-3 apothecia confluent but not agglomerating in dense groups, entirely immersed in the hymenium of the host, flat to hardly convex. Epithecium dull brown to chestnut brown, 15-20 μm high; hymenium colourless to pale brown, 30-40 μm high, hemiamyloid; paraphysoids branched and anastomosing, c. 1 μm thick, the terminal cells slightly enlarged, conglutinated by amorphous pigments, inbetween with granules of unclear origin; hypothecium colourless to pale brown, 40-50 μm high. Asci 8-spored, clavate, fissitunicate, with a tiny K/I+ blue ring basally in the tholus of the endoascus, Arthonia-type, 30-40 x 15-18 μm. Ascospores 1-septate, hardly constricted at septum, hyaline, obovate, 12-15(-16) x 4-5(-6) μm, the upper cell distinctly wider and longer, not halonate. Pycnidia not visible from the outside, embedded in ascomatal structures, subspherical, with brown walls. Conidia hyaline, bacilliform, 5-6 x c. 1 μm. Photobiont absent. Chemistry without lichen substances.
Note: An apparently rare species known from the mountains of Central and Southern Europe, growing on species of the Lecanora polytropa-complex.
Source: Hafellner, J., & Grube, M. (2023). Arthonia epipolytropa and Arthonia subclemens, two new lichenicolous species on Lecanora polytropa, with a key to the microfungi known on this common species. The Lichenologist, 55(5), 241-251. doi:10.1017/S0024282923000397