Platytrachelaceae H. W. Shen & Z. L. Luo 2026, fam. nov.

Platytrachelaceae H. W. Shen & Z. L. Luo fam. nov. Etymology. The family name Platytrachelaceae is derived from the type genus Platytrachelon. Type genus. Platytrachelon Réblová, detailed description and illustrations by Réblová (2013). Description. Saprobic on decaying wood. Asexual morph: Hyphomycetous. Mycelium immersed to superficial, composed of pale brown to brown, septate, branched hyphae. Conidiophores semi-macronematous to macronematous, mononematous, cylindrical, septate, unbranched, or reduced to conidiogenous cells. Conidiogenous cells enteroblastic, mono- to polyblastic, phialidic, polytretic, integrated or discrete, terminal or intercalary, cylindrical, clavate, ampulliform, spherical, sympodial, with denticulate or collarette, proliferating or non-proliferating. Conidia solitary or in short chains, hyaline to dark brown, ellipsoidal, obovoid to cylindrical, obclavate to rostrate, falcate or filiform, aseptate to multi-septate, with or without a sheath and appendages. Sexual morph: Ascomata immersed to superficial, subglobose to globose, dark brown to black, uniloculate. Necks central, cylindrical, ostiolate. Peridium leathery, two-layered. Paraphyses hyaline, branched, septate. Asci 8 - spored, unitunicate, cylindric-clavate, long pedicellate, with an apical annulus. Ascospores uniseriate, hyaline, fusiform, septate. Accepted genera. Aquimonospora, Multiseptisporium, Paradiplococcium, and Platytrachelon. Notes. The new family Platytrachelaceae is proposed to accommodate Multiseptisporium gen. nov. and three previously monotypic genera, Aquimonospora, Paradiplococcium, and Platytrachelon, which were formerly placed in Diaporthomycetidae genera incertae sedis and Sordariomycetes genera incertae sedis (Hyde et al. 2024). In our multi-gene phylogenetic analyses, these four genera consistently formed an independent clade, clearly distinct from all currently recognized families within Diaporthomycetidae families incertae sedis (Fig. 1, Suppl. material 1: fig. S 1). Consistent results were also recovered in single-gene maximum likelihood analyses, in which Platytrachelaceae repeatedly emerged as an independent lineage distinct from other families and orders within Diaporthomycetidae (Suppl. material 1: figs S 2 – S 6). However, due to relatively low support values for the backbone of this lineage, we tentatively place it in Diaporthomycetidae families incertae sedis. The family is typified by the genus Platytrachelon, which was introduced by Réblová (2013) to accommodate P. abietis (formerly Ceratosphaeria abietis), based on a combination of morphological characteristics and phylogenetic placement. Platytrachelon abietis was originally described based on its sexual morph, and subsequent studies documented its asexual morph on PCA medium, including the presence of synanamorphs (Réblová 2013). Although Platytrachelon remains monotypic, it is currently the only genus within Platytrachelaceae for which both sexual and asexual morphs have been documented. This morphological completeness supports the designation of Platytrachelon as the type genus of Platytrachelaceae.