Neopetractis Ertz gen. nov.

MycoBank number: MB 836497; Index Fungorum number: IF 836497; Facesoffungi number: FoF 13850;

Similar to Petractis but differing from the type of that genus (P. clausa, which associates with a cyanobacterial photobiont) in associating with a trentepohlioid photobiont.

Type species: Neopetractis luetkemuelleri (Zahlbr.) Ertz.

Description: (based mainly on the descriptions in Orange (2009) and Vězda (1965)). Thallus crustose, endolithic or semi-epilithic, continuous, rarely with fine cracks, smooth to minutely rugose, whitish grey or pale pink, ecorticate. Photobiont trentepohlioid.

Apothecia immersed, at first perithecioid, finally with a slightly to rather widely expanded disc; margin slightly raised, of the same colour as the thallus or slightly paler, with or without radial cracks, up to 0.5 mm diam.; disc beige-pink to pale brown, smooth, concave or flat, sunken below level of margin. Exciple thin, colourless or yellowish; cells angular, isodiametric to oblong. Hymenium colourless, I− or I+ faint blue, KI+ blue. Hypothecium thin, colourless. Paraphyses simple, apex not or slightly widened. Asci narrowly clavate, thin-walled, 8-spored, KI+ blue. Ascospores hyaline, ellipsoid, 3– 5-transversally septate to submuriform (with 1–2 additional longitudinal septa), medium-sized (c. 16–25 × 5.5–10 μm), with a distinct gelatinous sheath, c. 2–4 μm thick.

Conidiomata pycnidia, immersed in the thallus; conidiogenous cells holoblastic, not proliferating; conidia colourless, simple or formed of irregular multicellular clusters.

Chemistry: No lichen substances detected by TLC.

Etymology: The name reflects its morphological similarity to the cyanolichen genus Petractis.

Discussion: Neopetractis differs from Petractis in having a trentepohlioid photobiont and from Gyalecta s. lat. in having ascospores with a thick gelatinous sheath. Orange (2009) described P. nodispora, which is the sister species of P. luetkemuelleri in his molecular study. In our phylogenetic tree, these two Petractis species form a lineage close to the genus Ramonia and are distantly related to Petractis clausa. Because of the different photobiont and the distinct phylogenetic position, both species are transferred to the new genus Neopetractis (see also general discussion below). Petractis crozalsii (B. de Lesd.) Clauzade & Cl. Roux is a species with non-halonate ascospores and is now considered to be a species of Gyalecta closely related to Gyalecta hypoleuca (Ach.) Zahlbr. (Roux et al. 2008), thus leaving Petractis as a monotypic genus. Both species of Neopetractis grow on calcareous rocks.