Annulatascus K.D. Hyde, Aust. Syst. Bot. 5(1): 118 (1992)

Index fungorum number: IF25398; 17 morphological species (Species Fungorum 2020), 7 species with sequence data.

Saprobic on submerged wood. Sexual morph: Ascomata clustered or separate, brown to black, superficial, semi-immersed or immersed, solitary or gregarious, globose or subglobose, immersed or semi-immersed, carbonaceous or coriaceous, ostiolate, periphysate. Peridium comprising several layers of cells of textura angularis, or pseudoparenchymatous, or melanized angular cells. Hamathecium comprising paraphyses which are hyaline, septate and taper distally. Asci 8-spored, unitunicate, cylindrical, pedicellate, with a massive bipartite apical ring. Ascospores unicellular to multi-septate, uniseriate to overlapping biseriate, ellipsoidal or fusiform or lunate or citriform, hyaline to pale brown, verrucose or smooth, guttulate or non-guttulate, with or without sheath and appendages. Asexual morph: Undetermined.

Type species: Annulatascus velatispora K.D. Hyde, Aust. Syst. Bot. 5(1): 118 (1992).

Notes: Annulatascus is the type genus of Annulatascaceae and was introduced by Hyde (1992b) based on two tropical freshwater taxa, A. velatispora as the type species and A. bipolaris. However, the holotype of A. velatisporus was in poor condition as herbarium material had only a few ascomata. Thus, Dayarathne et al. (2016a) designated an epitype, which was collected from submerged wood in a river, at Millaa Millaa Falls, north Queensland, Australia, based on morphological examination and DNA sequences. The genus presently contains 19 epithets (Index Fungorum 2020) and molecular data has demonstrated that this genus is polyphyletic (AbdelWahab et al. 2011, Luo et al. 2015) and confirmed that placement of species in this genus based solely on the relatively massive apical ascal ring is not very reliable (Abdel-Wahab et al. 2011, Luo et al. 2015). In our phylogenetic analyses, Annulatascus nilensis does not cluster within Annulatascus, but is basal to Ascitendus, Longicollum and Submersisphaeria with low bootstrap support. Annulatascus nilensis also formed a weakly-supported clade with members of Annulatascus (Abdel-Wahab et al. 2011, Luo et al. 2019). Fresh collections and multigene phylogenies are needed to resolve the taxonomy of this group of fungi.