Thallus: indistinct, thin; upper surface: membrane-like, evanescent, pale gray, greenish when wet; prothallus: absent; Perithecia: 0.1-0.3 mm diam., sessile to slightly immersed, black, rounded to pyriform, discrete, very rarely 2-4 contiguous; exciple: dull greenish above (K+ violaceous), paler below, 15-20 µm thick; asci: cylindrical, 8-spored; ascospores: colorless, submuriform, elongate or narrowly ellipsoid, 22-33 x 7-10 µm; Pycnidia: not seen; Spot tests: all negative; Secondary metabolites: none detected.; Substrate and ecology: encrusting dead mosses and dead lichen thalli, rarely on acid soil and plant detritus in upper montane to alpine habitats; World distribution: mountains of central Europe, northern Europe, North America; Sonoran distribution: only known from one locality in Apache National Forest in Arizona at 3000 m.; Notes: This species is characterized by an indistinct thallus, small sessile black perithecia with a dull greenish exciple and elongate submuriform ascospores. Another species known from North America is Protothelenella sphinctrinoides (Nyl.) H. Mayrhofer & Poelt, which is distinguished by larger partly immersed perithecia and larger muriform ascospores.
Regularity: Regularly occurring