Acanthostigmella Höhn., Annls mycol. 3(4): 327 (1905).
Index Fungorum number: IF 17; Facesoffungi number: FoF 00219, 6 morphological species (Species Fungorum 2021), 0 species with molecular data.
Saprobic on dead stems of grasses. Sexual morph: Ascomata superficial, solitary, scattered, globose-subglobose, dark brown, with 23–74 μm long dark brown, apically acute, septate setae, darkened papilla and ostiole. Peridium thin-walled, composed of brown to red brown, 3– 6.5 μm diam. cells of textura angularis. Hamathecium lacking pseudoparaphyses. Asci 8-spored, bitunicate, oblong, subclavate to broadly obovoid, with a blunt, wide, rounded pedicel, almost apedicellate. Ascospores 2–3- seriate in ascus, ellipsoid, fusoid, ends rounded, 2–3- septate, constricted at septum, yellow brown, smooth walled. Asexual morph: hyphomycetous, helicosporous, dictyosporous and xenosporiumlike (Hyde et al. 2011).
Type species: Acanthostigmella genuflexa Höhn.
Notes: Acanthostigmella was introduced by Von Höhnel (1905) with A. genuflexa as type species. Acanthostigmella is different from all genera in Tubeufiaceae in having small ascomata comprising a distinct papilla surrounded by setae, absence of pseudoparaphyses, largely obovoid to fusoid asci, and 2–3-septate, yellow brown ascospores (von Höhnel 1905; Barr 1977). Barr (1977;1980) and Rossman (1987) suggested the placement of Acanthostigmella in Herpotrichiellaceae (Chaetothryriales) rather than Tubeufiaceae. Untereiner et al. (1995) placed Acanthostigmella in Dothideomycetes based on molecular data of Acanthostigmella brevispina. Later, Boonmee et al. (2014) re-examined the holotype specimen of A. genuflexa from FH and placed the genus in Dothideomycetes genera incertae sedis. No asexual morph is linked to the generic type. More taxa and DNA sequence data is required to solve the correct taxonomic placement of the genus.