New Zealand: "Nelson Tophouse Saddle; 22.i.1969, leg. Horak (PDD, 27127: holotype; ZT, 69/4: isotype)". "Canterbury, Mt Grey, Kowai Bush; 22.1.69, leg. Horak (ZT, 67/205)." "Westcoast, Lake Haupiri, Kopara; 15.xii. 1967, leg. Horak (ZT, 67/257)."

Pileus 10-40 mm diam., hemispherical when young soon convex, conico-convex or campanulate to umbonate-expanded; yellow brown, golden brown, at disc with red-brown to fulvous tinge (rarely black-brown); dry, centre covered with squarrose scales and squamules, fibrillose to rimose towards estriate margin, veil remnants absent. Lamellae adnexed to sinuate-adnate, ventricose, crowded (L -18, 1 -3); pallid or grey in young carpophores turning argillaceous or olive-brownish, edge concolorous or albofimbriate. Stipe 20-50 x 2.5-4 mm, cylindrical, equal; whitish yellowish to yellowish brownish, apex sub pubescent or fibrillose, towards base with concolorous sub-squarrose to woolly fibrils or squamules, veil remnants absent; dry, hollow, single and cespitose. Context pale brownish. Odour and taste not distinctive. Chemical reactions on pileus: KOH-negative.
Spores 6.5-8.5 x 4-5 µm, amygdaliform, brown, smooth, suprahilar depression absent. Basidia 20-26 x 6-8 µm, 4-spored. Cheilo- and pleurocystidia 35-60 x 10-17 µm, fusoid to lageniform, metuloid ("2 µm diam. near apex), hyaline, encrusted with crystals. Caulocystidia clavate to subfusoid, thin-walled, with and without crystals. Cuticle a trichoderm of cylindrical hyphae (5-10 µm diam.), encrusted with yellow-brown (KOH) pigment. Clamp connections present.

On soil among litter and moss (also Sphagnum) under Nothofagus (N. fusca, N. cliffortioides). New Zealand.

Pileo -40 mm lato, convexo, convexo-conico vel campanulato, luteo brunneo vel fulvo, squamato-fibrilloso, sicco. Lamellis adnexis, pallidis dein argillaceo-olivaceis. Stipite -50 x -4 mm, cylindrico, pileo concolori vel pallidiore, fibrilloso ad apicem, squarroso basim versus. Odore nullo. Sporis 6.5-8.5 x 4-5 µm, amygdaliformibus. Cystidiis fusoideis, crasse tunicatis, incrustatis. Habitatio ad terram in silvis nothofagineis. Nova Zeiandia. Typus (PDD, 27127).

According to my observations I. scabriuscula is widely distributed in the beech forests of New Zealand. Its morphology varies considerably but the following three macroscopical characters help to identify this taxon in the field: yellow-brown to golden-brown, scaly pileus, argillaceous lamellae (often with an olive tinge), and pale yellow-brown scales towards the base of the stipe.