Cortinarius fuscobovinaster is an agaric fungus in the family Cortinariaceae, formally described in 2013 based on specimens collected from limestone woodland near Steinkjer, Norway. The species features a greyish-brown cap measuring 2.5âÂÂ7 centimetres across, moderately spaced gills that transition from pale brown to dark reddish-brown, and a whitish stipe that quickly browns with age. It fruits in early September in coniferous forests on lime-rich soils throughout central and northern Europe's hemiboreal and southern boreal zones, primarily in well-preserved natural forest reserves.
Cortinarius fuscobovinaster was formally described in 2013 by Ilkka Kytövuori, Tuula Niskanen, and Kare Liimatainen following combined morphological study and DNA sequencing (ITS and rpb2 regions). The epithet fuscobovinaster â from Latin () and ("of C. bovinus") â alludes to both its darker specimens when dried and found in herbaria (dried specimens in Latin: specimina exsiccata) and its close resemblance to Cortinarius bovinidus. The holotype was collected on 5 September 2009 by Kytövuori in a karst (limestone) woodland near Steinkjer, Nord-Trøndelag, Norway. The type collection (Kytövuori 09âÂÂ537) was deposited in the herbarium of the University of Helsinki.
The cap (pileus) of C. fuscobovinaster measures 2.5âÂÂ7 cm across. Initially hemispherical with an inrolled margin, it soon flattens to a low convex or nearly level shape, occasionally bearing a small central bump (umbo). Its surface is covered in fine, innate fibres (fibrillose) and appears greyishâÂÂbrown when fresh; as it dries (hygrophanous), streaks of paler, yellowishâÂÂbrown appear. The gills are moderately spaced and notchâÂÂattached (emarginate) to the stipe, transitioning from pale brown to dark reddishâÂÂbrown, and sometimes darkening further when handled.
The stipe stands 3âÂÂ13 cm tall and 0.7âÂÂ1.3 cm thick at the apex (expanding to 1.5âÂÂ3.0 cm at the base). It is roughly cylindrical to clubâÂÂshaped and initially clothed in whitish fibrils that soon brown. Remnants of the universal veil form a woolly band around the midâÂÂstipe. The fleshis uniform pale greyishâÂÂbrown, darkening to nearâÂÂblack at the stipe base in mature specimens, and gives off no distinctive odour.
Microscopically, spores measure 8.8âÂÂ10.7 by 5.4âÂÂ6.3 üm (average 9.4âÂÂ10.1 by 5.8âÂÂ6.2 üm). They are narrowly ellipsoid to tearâÂÂshaped (lacrymoid), with a small suprahilar depression (where the spore attaches to the basidium), and bear a dense covering of fine to moderate warts (verrucose ornamentation). In Melzer's reagent these spores stain reddishâÂÂbrown (a dextrinoid reaction), a diagnostic chemical response. The central gill tissue (trama) consists of smooth, oliveâÂÂtinted hyphae, while the gill edge carries mostly globose to sphaeropedunculate (shortâÂÂstalked) cells. The cap cuticle (pileipellis) is a thin layer of pale brownish hyphae, largely smooth but sometimes showing fine, zebraâÂÂstriped pigment encrustations; a distinct layer of almost colourless cells (hypoderm) lies beneath. Clamp connections (hookâÂÂlike bridges between adjacent hyphal cells) are present throughout the mushroom's tissues.
Cortinarius fuscobovinaster fruits in early September in mesic to dryish coniferous forests on calcareous (limeâÂÂrich) soils. It has been found in mature spruceâÂÂdominated stands, mixed pineâÂÂspruce woodlands, and even on exposed limestone ridges. All known records lie within the hemiboreal and southern borealzones of central and northern Europe, where the species remains rare and mostly confined to wellâÂÂpreserved natural forest reserves.