Basidiocarps: annual brackets, applanate (flattened) to slightly convex, dimidiate, fan shaped to rounded, up to 15cm wide and long, 1 to 5 cm thick, fleshy and flexible when fresh then hard but friable when dry and light of weight; upper surface finely velutinate when young but soon glabrous, at first whitish, then yellow and finally brown becoming darker from the base with age, often pitted and slightly tuberculate; margin rounded, finely pubescent and pale brown; pore surface smooth and white when young, darker when bruised, later dirty brown and cracked. Pores: circular, 2-4 per mm. Context: much thicker than tubes, white, hard and tough up to 4 cm thick; tube layer concolorous with pore surface, up to 4 mm thick. Hyphal system: dimitic (consisting of two types) in context, monomitic (consisting of one type) in trama. Cystidia: absent, fusoid cystidioles present. Basidia: 25-30 x 7-9 μm, narrowly clavate, four spored, with a basal clamp. Spores: 6-8 x 2.5-3.5 μm, cylindrical, fusiform, tapering to the base, usually characteristically bent close to the apex, hyaline, smooth, thin walled.
Only found on the exposed heartwood of living Quercus spp (oaks). Usually old or mature trees but can occur on younger trees where damage has exposed heartwood.