Anamorph: conidiomata absent. Conidiophores in large irregular clusters or in a palisade on the stroma surface, short, dark brown, frequently branched with clusters of conidiogenous cells or with the conidiogenous cells simply the terminal cell of the conidiophore. Conidiogenous cells 12-21 x 2.5-3 (-4) µm, hyaline to pale brown, irregular in form but ± cylindrical, proliferating sympodially and usually with multiple denticles. Conidia 11-18 x 2-2.5 (-3) µm, irregularly falcate, the ends somewhat attentuated and ± acute, hyaline, aseptate, smooth- and thin-walled.
Teleomorph: stroma effuse, in wood or bark, strongly lifting and disrupting the substratum surface in broad plates, the surface black, delimited by a black zone line visible within the wood, in young material covered in tomentose brown hyphae. Ostioles separately emergent, very prominent, 200-400 µm diam. and 2-3 mm in height, ± cylindrical, ± furrowed or deeply split. Ascomata perithecia, 600-700 µm diam. and to 1.1 mm tall, in a single layer, close together and distorted due to contact with other perithecia, spherical to ovoid, with a long neck. Interascal tissue of very thin-walled tapering paraphyses, often deliquescent at maturity. Asci 25-35 x 5-6 µm (spore-bearing part, with a long tapering stalk 35-75 µm in length, with a small apical ring that blues in iodine, 8-spored. Ascospores (5.5-) 6-7.5 (-9) x (1.5-) 1.8-2.2 µm, allantoid, aseptate, pale yellow, thin- and smooth-walled, without an epispore or gelatinous sheath.
Not formally assessed but common. It would certainly be considered as of Least Concern.
On dead trunks and branches of Fagus sylvatica.
Throghout the British Isles as far north as central Scotland, also in Northern Ireland and ROI.