Arthopyreniaceae Walt. Watson, New Phytol. 28: 107 (1929).
MycoBank number: MB 80473; Index Fungorum number: IF 80473; Facesoffungi number: FoF 08161, 61 species.
Non-lichenized on bark in terrestrial, temperate forest habitats. Thallus reduced, ecorticate, whitish or indistinct. Sexual morph: Ascomata scattered, prominent, brown-black, hemisphaerical, carbonaceous, ostiolate. Ostiole round. Involucrellum and excipulum are indistinct, dark brown, carbonized. Excipulum dense, proso- to paraplectenchymatous in thin sections, brown. Hamathecium comprising densely packed, paraphysoids connected to both the base and the top of the centrum, hyaline, straight to irregularly bent, branched and anastomosing. Asci forming in locules between the paraphysiods, 8-spored, fissitunicate, bitunicate, broadly clavate to cylindric clavate, short-pedicellate, with rather broad, non-amyloid ocular chamber. Ascospores irregularly arranged to 2-seriate, oblong with the proximal end slightly tapering, hyaline, occasionally brownish when become old, 1–3-septate, eusepta and rectangular lumina, not or very slightly constricted at the septa, the upper cells often slightly larger than the lower cells, smooth-walled. Asexual morph: Pycnidia erumpent to prominent, visible as brown-black dots. Conidia acrogenous, either macro- or microconidia; macroconidia bacillar, hyaline, aseptate, 10–13 × 2–2.5μm; microconidia acicular, hyaline, aseptate, 7–14 × 0.8–1μm.
Chemistry – Unidentified perithecial wall pigment reacting K+ green.
Type – Arthopyrenia A. Massal.
Notes – Arthopyreniaceae was established by Watson (1929) to encompass the genera Acrocordia, Athrismidium, Arthopyrenia, Bottaria, Celothelium, Laurera, Leptorhaphis, Microthelia, Microtheliopsis, Polyblastiopsis, Pseudosagedia, Raciborskiella, and Tomaselli. It includes lichenized and some non-lichenizd fungi based on trentepohlioid photobiont and has branched, anastomosing paraphyses (Watson 1929). These genera were later assigned to different classes, orders and families (Harris 1975, 1995, Aproot et al. 2008, Nelsen et al. 2009, 2011a, Hyde et al. 2013). Subsequently, Arthopyreniaceae was synonymysed with Mycoporaceae (Riedl 1961, von Arx & Müller 1975) or Pleosporaceae (Poelt 1974, Harris 1975). Arthopyreniaceae was reestablished by Barr (1979a) and considered a synonym of Xanthopyreniaceae (Eriksson 1981). Presently this family comprises a single genus Arthopyrenia (Jaklitsch et al. 2016a, Lücking et al. 2017). However, Liu et al. (2017a) did not accept this family while Wijayawardene et al. (2017a) considered both Arthopyrenia and Magmopsis in Arthopyreniaceae. According to Index Fungorum 2020, there are two species of Magmopsis namely M. argilospila and M. pertenella. These species have been referred to incertae sedis and have characteristics such as nostociform cyanobacteria intermingled with mycelium, preformed ostiole, anastomosed paraphysoids with thin-walled ascospores (Grube 2005); no molecular data are available in Genbank (Wijayawardene et al. 2017a). Therefore, we keep Magmopsis in Dothideomycetes incertae sedis and consider only Arthopyrenia in Arthopyreniaceae. Based on phylogenetic analysis, Arthopyreniaceae is included in Pleosporales where it is close to bambusicolous species in Roussoella and thus, the delineation of this family needs to be assessed (Nelsen et al. 2009, Schoch et al. 2009, Zhang et al. 2009b, Hyde et al. 2013).