Nematothecium Syd. & P. Syd., Leafl. of Philipp. Bot. 5(no. 76): 1534 (1912).
MycoBank number: MB 3444; Index Fungorum number: IF 3444; Facesoffungi number: FoF 07882; 5 morphological species (Species Fungorum 2020), molecular data unavailable.
Type species: Nematothecium vinosum Syd. & P. Syd.
Notes: The genus was introduced from the Island of Palawan in the Philippines. Nematothecium is characterized by large mycelium colonies, irregular, superficial ascomata with dark red ascomata, bitunicate asci and elongate fusi- form, curved or flexuous, multi-septate, hyaline to red brown ascospores. Nematothecium was placed in Pseudoperisporiaceae by Kirk et al. (2008), Lumbsch and Huhndorf (2010), and Hyde et al. (2013). Boonmee et al. (2017) re-examined the holotype and lectotype of N. vinosum and concluded that the shape and septation of ascospores are typical of Tubeufiaceae, however, its habitat can differentiate them from Tubeufiaceae. Therefore, Nematothecium is placed in the new family Nematotheciaceae (Boonmee et al. 207).