Anamorph: Coniothyrium-like. Conidiomata to 500 µm broad, similar in appearance to the ascomata, stromatic, the wall composed of dark brown thick-walled polygonal cells externally, with an inner layer of thin-walled tissue. Conidiogenous cells formed from the inner peridial cells, doliiform, proliferating percurrently with annellations present. Conidia 5-7 x 3.5 µm, broadly ellipsoidal, ovoid or globose, pale olivaceous brown, aseptate, thin-walled, punctiform.
Teleomorph: Stroma well-developed, 5-20 mm broad, extensive and appearing superficial, or reduced and inconspicuous amongst fissures in host bark; erumpent through the periderm, the surface black, containing dense clusters of unilocular ascomata. Ascomata to 700 µm diam, developing as pustule-like extensions of the stroma, with a broad, often slightly papillate and collapsing ostiole. Peridium to 50 µm thick, with 2-3 outer layers of very thick-walled, dark brown, almost opaque cells, and inner layers of hyaline thin-walled cells. Asci 110-140 x 10-12 µm, cylindrical, short-stalked, fissitunicate, 8-spored. Ascospores 16-25 x 7-9 µm, with 3-5 transverse septa, usually with longitudinal and oblique septa, constricted at the transverse septa, the ends acute, brown, smooth, without mucous sheath or appendages.