Leptopeltidaceae Höhn. ex Trotter [as ‘Leptopeltineae’], Syll. fung. (Abellini) 24(2): 1255 (1928).

MycoBank number: MB 81594; Index Fungorum: IF 81594; Facesoffungi number: FoF 07969, 15 species.

Epiphytic on ferns (Aspidium), Aruncus, Potentilla and other flowering herbaceous plants as well as Connarus suberosus Planch. Sexual morph: Ascomata thyriothecial, superficial, visible as black dots or irregular on host surface, producing vegetative mycelium penetrating the host, solitary to gregarious, flattened, circular, round, elongate or irregular, or Y-shaped, easily removed from the host, brown to dark brown, waxy, in section lenticular, scutate, conical, or quadrilateral trapezoid, dehiscence by slit-like opening, or splitting of the upper wall. Peridium thin-walled, composed of reddish-brown to dark brown, isodiametric or polygonal upper-walled cells with a parallel or irregular arrangement, radiating from the centre, basal layer poorly developed, occasionally forming basal cell layers, arranged in a textura angularis in verical section. Hamathecium comprising broadly filamentous, septate, unbranch, tapering towards the apex, paraphyses, embedded in gelatinous matrix. Asci 8-spored, bitunicate, broadly cylindrical to cylindric-clavate, or subglobose to ampulliform, with obtuse to truncate or acutate apex, sesille to subsessile, with truncate base, ocular chamber indistinct, clearly visible when young. Ascospores overlapping 1–3-seriate, twisted or fasciculate, varied in shape, ellipsoidal, broadly fusiform, cylindrical, lunate, or muriform, with rounded to acute ends, hyaline, aseptate or septate, smooth-walled, with or without small guttules. Asexual morph: Hyphomycetous idriella-like (asexual morph of Dothiopeltis) and coelomycetous leptothyriumlike (asexual morph of Leptopeltis) (Wijayawardene et al. 2017b).

Type: Leptopeltis Höhn.

Notes: von Höhnel (1917) invalidly introduced Leptopeltidaceae as ‘Leptopeltineen’ and treated the family in Phacidiales. However, the family was validly introduced by Saccardo (1928). The familial concept contained highly heterogenous taxa which were described as epiphytic fungi having excipular or subcuticular, uni-loculate ascomata with longitudinal irregular scratch-like openings and hyaline, fusoid, two-celled ascospores with paraphyses (von Höhnel 1917; Holm and Holm 1977; Hyde et al. 2013). von Höhnel (1917) included 12 genera in this family, Bifusella, Coccomyces, Duplicaria, Entopeltis, Haplophyse, Leptopeltella, Leptopeltis, Lophodermina, Phacidina, Schizothyrioma, Thyriopsis and Vizella. The family has a long historical discussion by various authors and many genera were included and excluded from this family (Petrak 1947a, b; von Arx and Müller 1975; Holm and Holm 1977; Eriksson 1981; Lumbsch and Huhndorf 2010; Hyde et al. 2013). Holm and Holm (1977) mentioned that taxa in Leptopeltidaceae have unitunicate asci as they could not find the “Jack in the box” dehiscence exhibited by Leptopeltis asci based on their observation under the transmission electron microscope (TEM). Eriksson (1981) disagreed with Holm and Holm (1977) and demonstrated bitunicate asci with “Jack in the box” dehiscence in Leptopeltidaceae as he had found the endotunica and ectotunica layers of the asci. However, there was no sharp delimitation between endotunica and ectotunica in ascomycetes. Hence, it is difficult to name the bitunicate or unitunicate asci in many cases of which Leptopeltis is one of these cases (Eriksson 1981; Hyde et al. 2013).

Hyde et al. (2013) re-circumscribed genera in Leptopeltidaceae following the lists of Lumbsch and Huhndorf (2010). Based on the generic type studies, Hyde et al. (2013) accepted five genera in Leptopeltidaceae viz. Leptopeltis, Dothiopeltis, Nannfeldtia Ronnigeria and Staibia and classified the family in Dothideomycetes, family incertae sedis. Hyde et al. (2013) excluded Phacidina from Leptopeltidaceae as the type genus, P. gracilis has unitunicate asci, with J+, subapical ring. However, Wijayawardene et al. (2018) listed the genus in Leptopeltidaceae. We re-examine the type of genera in Leptopeltidaceae and exclude Nannfeldtia from Leptopeltidaceae. The generic type of Nannfeldtia, N. atra has morphological similarity with taxa in Leotiomycetes in having apothecial ascomata, apically swollen paraphyses and unitunicate asci, with J+ apex (Phookamsak, pers. comm.). Therefore, we accept four genera: Leptopeltis, Dothiopeltis, Ronnigeria and Staibia in Leptopeltidaceae. However, these genera lack molecular data to clarify their phylogenetic affinities, and their morphological characteristics are heterogeneous. A taxonomic revision of genera in this family based on molecular data awaits study and will resolve whether these taxa are Dothideomycetes or belong in another class.