Thaxteriella Petr., Annls mycol. 22(1/2): 63 (1924).
Saprobic on dead bark. Mycelium forming a dense velvety subiculum on surface of bark, comprising black hyphae. Sexual state:Ascomata superficial or slightly embedded on a basal subiculum, solitary or densely gregarious, globose to turbinate, black, shiny, often with small apical papillae at central ostiolate apex, often collapses when dry. Peridium comprising two strata, outer layer of thick-walled, dark brown cells of textura angularis and inner layer of brown cells of textura globosa. The apical region is composed of less thick-walled cells that disintegrate to form an ostiole. Hamathecium composed of filamentous, septate, branched, anastomosing,hyaline pseudoparaphyses. Asci 8-spored, bitunicate, cylindrical to broadly clavate or subclavate, usually with a short pedicel, thickened at apex withan ocular chamber. Ascospores cylindrical to long fusiform, tapering towardsrounded to sub-acute ends, trans-septate, hyaline.Asexual state: hyphomycetous, helicosporous.Conidiophoreserect, up to 180 µm long, brown to dark brown, light-coloured at apex. Conidia 17–21 µm diam., pleurogenous, developing on cylindrical pegs arising form cells of conidiophores, 1½–1¾ times coiled, 5–12-septate, hyaline to pale olivaceous brown (from Sivanesan 1984).
Notes: No sequences exist in GenBank for the type species of Thaxteriella, T. corticola and other species in the genus. Thaxteriella pezizula was included in this genus by Petrak (1953) based on morphological consistency with the genus, as recognized by globose or oblate globose, darkly pigmented, shiny, ascomata, collapsing in the middle when dry and filiform ascospores (Berkeley 1876; Linder 1929; Barr 1980; Sivanesan 1984). In addition, Linder (1929) determined thatThaxteriella pezizula produced a helicoma-likehyphomycetous asexual state. Thaxteriella may therefore be a synonym of Helicoma. Boonmee et al. (2011) introduced Thaxteriella inthanonensisas a new species in Thaxteriella, and this species clusters with Helicoma sensu stricto as reported
Type species:Thaxteriella corticola Petr., Annls mycol. 22(1/2): 63 (1924)