Anamorph: referable to the form-genus Phaeoacremonium. Conidiophores (11–)16–20(–33) x (1.5–)2(–2.5) µm, mostly unbranched, subhyaline to hyaline, the apical cells supporting one or two conidiogenous cells. Conidiogenous cells terminal or lateral, tapering towards the apex, ± hyaline, proliferating percurrently with inconspicuous collarettes, dimorphic. Type 1: (2–)3–4(–6) x 1–2 µm, cylindrical to subcylindrical. Type 2: (5–)7–9 (–16) x (1.5–)2(–2.5) µm, elongate–ampulliform and attenuated at the base, or subcylindrical, tapering towards the apex. Conidia 4–5 x 1(–1.5) µm, mostly cylindric–ellipsoidal or suballantoid, becoming biguttulate with age. Teleomorph: stromata absent. Ascomata 335–500(–670) µm diam. and 340–500(–700) µm high, papillate or with necks to 0.5 mm and straight or curved, dark brown to black, ± smooth, gregarious to crowded, immersed beneath bark and superficial to semi-immersed on bare wood. Wall 50–70 µm thick near the base, 75–100 µm thick in the upper part, leathery to fragile, two-layered; outer layer of reddish brown, thick-walled angular cells, inner layer of thinner-walled, subhyaline to hyaline elongate and compressed cells. Neck periphysate. Interascal tissue paraphysis-like, persistent, septate, slightly constricted at the septa, 3–6 µm diam. near the base, tapering to ca 2–2.5 µm, significantly longer than the asci. Ascogenous hyphae 20–45 µm long, abundant, persistent, sympodially elongating, bearing a crown of mature attached asci and ascus remnants. Asci (15-)22-27.5 x 3-4 µm, clavate, shortly stipitate, with broadly rounded to truncate apices, thick-walled at the apex but without visible discharge mechanism, 8-spored. Ascospores arranged biseriately, 3-5.5(-6) x 0.5-1(-1.5) µm, allantoid to nearly straight, hyaline, aseptate, smooth- and thin-walled, without a gelatinous sheath or appendages.