Microtheciumzobelii Corda, Icon. fung. (Prague) 5: 74. 1842. Representative strain: NBRC 9442.

Ascomata ostiolate or not, superficial or immersed, globose to subglobose or pyriform, yellowish-orange, orange-brown or reddish, tomentose or glabrous; necks short or absent, conical, composed of angular cells similar to those of the ascomatal wall, usually with a crown of hyaline, septate, smooth- and thick-walled setae around the ostiole; ascomatal wall membranaceous, translucent, of textura angularis. Periphyses present. Paraphyses absent. Asci 8-spored, clavate, rounded at apex, without apical structures, thin-walled, evanescent. Ascospores one-celled, at first hyaline, becoming brown to dark brown when mature, ellipsoidal, fusiform, navicular, citriform, plataniform or spindle-shaped, smooth, reticulate, pitted or wrinkled, with a terminal apiculate or depressed germ pore at each end. Asexual morph phialidic, hyaline. Bulbils usually produced, pale orange to reddish-orange.

Microthecium has translucent ascomata of textura angularis, cellular necks short or absent, ascospores smooth-walled or ornamented with a depressed or apiculate germ pore at each end, often producing bulbils and a phialidic asexual morph. Dactylidispora, Pustulipora and Pseudomicrothecium produce ascomata similar to Microthecium. However, the two first genera can be distinguished by the presence of a raised rim and blistered structure surrounding the germ pores of the ascospores, respectively, while Pseudomicrothecium differs in the production of 2-spored asci and ascospores with indistinct germ pores.

The species Mi.africanum, Mi.beatonii, Mi.brevirostratum, Mi.episphaerium, Mi.foveolatum, Mi.geoporae, Mi.hypomyces, Mi.internum, Mi.lenticulare, Mi.marchicum, Mi.masonii, Mi.micropertusum, Mi.moureai, Mi.nectrioides, Mi.pegleri and Mi.perplexum were not included in the phylogenetic study because we could not locate any specimens since the holotypes or living cultures of most of them are not available. However, these species were transferred to Microthecium based on their complete and well-illustrated descriptions.