A fungus with fruitbodies resembling small white nail heads or golf tees of 3-8 mm diam., the flat surface covered in sparse, evenly spaced black dots, growing on rabbit, hare, horse, or pony dung. Morphologically very similar to Poronia punctata, but with much larger ascospores.
Stromata almost sessile (unstalked) to stipitate (stalked), shallow-cupulate, with a superficial upper portion (disc) containing perithecia, and a lower one partly or fully immersed in the substratum, formed of rather pale, 4-15 μm diam., interwoven, wavy, septate, easily separable, thick-walled, often traversely striate hyphae. Disc 3-8 mm diam., white, flat, black dotted with protruding perithecial necks, and with a slightly raised, inflexed margin. Basal peduncle (stalk) 1-10 mm long, inversely conical, sometimes branching into two, dark brown-blackish, slightly tormentose (with matted “hair”), almost leathery. Perithecia (sub)globose, 500-700 x 450-650 μm, arranged on a single plane, fully immersed in the stroma, except for the neck, ostiolate (with openings), membranous, smooth, very pale brown, with a nipple-like, leathery, blackish neck. Peridium (ascomatal or perithecial wall) layered: 1) endostratum pseudoparenchymatous (inner layer like plant parenchyma cells) formed of pale, thin-walled, polygonal cells, 5-10 μm diam., 2) exostratum (outside layer) a textura intricata of crowded, interwoven, septate, thick-walled, pale yellowish-brown hyphae, 2-5 μm diam. Paraphyses exceeding the asci, cylindric, septate, 5-7 μm diam., simple or branched at the base, tapering towards the apex, containing a few hyaline vacuoles. Asci 8-spored, amyloid (reacting yellow/brown in iodine, e.g. Lugol’s or Melzer’s solution) , 175-200 x 20-25 (-40) μm, cylindric or sometimes subclavate, roundish at the apex, with a short, lobate stalk. Ascospores one-celled, obliquely or transversely uniseriate (in a single row), hyaline in the early stages, yellowish later and dark brown at maturity, (24-)26.2-31.5 x 14.7-15.8 μm, ellipsoidal or narrowly ovoid, sometimes inequilateral (length/width ratio or Q=1.51-2.22), surrounded by a broad gelatinous sheath, smooth, rather thick-walled, provided with a slightly eccentric germ slit, 11-13 μm long.
Description adapted from Doveri, F. (2004). Fungi fimicoli italici. A guide to the recognition of basidiomycetes and ascomycetes living on faecal material. Associazione Micologica Bresadola, Trento.