Bonomyces pseudoarnoldii L. Fan & N. Mao 2022, sp. nov

Bonomyces pseudoarnoldii L. Fan & N. Mao, sp. nov. (Figs. 3, 4) MycoBank:— MB841875 Diagnosis:—differing from the phylogenetically and morphologically closest related species B. arnoldii by its crowded lamellae, absence of granules at the top of the stipe, well-differentiated mediostratum and stipitipellis, genetic profile, and distribution in north China. Etymology:—‘ pseudoarnoldii ’, refers to this species being similar to B. arnoldii. Holotype:— CHINA. Shanxi Province, Linfen City, Yicheng County, Zhongtiaoshan Mt., 1950 m elev., 8 July 2021, on the ground under Pinus armandi, N. Mao MNM 239 (BJTC FM1672). Description:— Pileus 12–49 mm, at first convex, then flat to slightly depressed or umbilicate; margin not striate, revolute or flat when young, later slightly uplifted and wavy, sometimes split; surface dry, finely to coarsely fibrillose near the margin, occasionally cracking into minute squamules towards the center; reddish brown (#b95d30) to dark brown (#a56829), pale orange (#e67028), sometimes light yellow (#f3bc9b) or dark reddish brown (#3f1010) in the center. Lamellae 1.5–3.0 mm broad, L = 40‒60, l = 1‒3, crowded, subdecurrent to decurrent, whitish (#ff0000), becoming beige (#f5f5dc), edge turning reddish brown (#b95d30) with age. Stipe central, 18–45 × 3–9 mm, terete, usually equal, occasionally inflated at the apex and slightly tapering at base, granules absent at the top, sometimes curved, longitudinally fibrillose, solid, pale white (#fafafa) to reddish brown (#b95d30) or pale orange (#ee9e6d), with a cluster of large white rhizomorphs at the base. Context white when young later pale brown under the pileus and stipe surface. Odor not recorded. Taste not recorded. Spore print white. Basidiospores [120/4/3] (6.5–)7–8.5(–9) × (4–)4.5–5.5(–6) μm (avg. ± SD = 7.6 ± 0.65 × 4.8 ± 0.57 μm), [Q = (1.35–) 1.40–1.75 (–1.90), Q av = 1.58 ± 0.16], mostly oblong-ellipsoid or amygdaliform in side-view, a few somewhat cylindrical, usually uni-guttulate, smooth, slightly thick-walled (0.3–0.6 µm), with a thick lateral apiculus. Basidia (27–)30–35(–37) × 5–8 μm, mostly 4–spored, occasionally 2–spored, cylindrical to clavate, mostly hyaline, with sterigmata 3–6 μm long. Subhymenium 10–15 µm thick, pavimentous (bottom of hymenophore), weakly developed, made of small polygonal elements 2–4 µm wide. Hymenopodium, 15–20 µm thick, slightly divergent, composed of slender hyphae 1.5–5 µm wide. Mediostratum 70–105 µm thick, well differentiated, regular, composed of parallel hyphae 3–9 μm diam, smooth, colorless. Hymenial cystidia not seen. Pileipellis a trichoderm, 120–150 µm thick, composed of parallel cylindrical to clavate hyphae, 3–11 μm in diam, smooth, with walls sometimes slightly thickened, with yellow to brown minute intracellular pigment, often with numerous cystidioid terminal elements measuring about 30–55 × 5–9(–13) μm, cylindrical to narrowly clavate or sometimes irregular, prostrate or erect, in fascicles. Subpellis not differentiated. Stipitipellis well-differentiated, 90–105 µm thick, composed of parallel hyphae 2.5–6 μm diam. with pale yellow to light brown content, thin-walled. Stipititrama well-differentiated, made of parallel hyaline hyphae 2.5–9.0 µm wide. Clamp connections present in all tissues. Habit, habitat and distribution:—Solitary or scattered, on the ground in conifer forests dominated by Pinus armandi, known from the north of China. Additional specimens examined:— CHINA. Shanxi Province, Linfen City, Yicheng County, Zhongtiaoshan Ms., 35°29’41’’N, 111°54’15’’E, 1950 m elev., 8 July 2021, on ground under Pinus armandi, N. Mao MNM 238 (BJTC FM1671); ibid. 35°29’51’’N, 111°55’1’’E, 1920 m elev., 8 July 2021, on ground under Pinus armandi, N. Mao MNM 240 (BJTC FM1673).
Published as part of Mao, Ning, Lv, Jing-Chong, Zhao, Tao-Yu & Fan, Li, 2022, Bonomyces pseudoarnoldii (Biannulariaceae, Agaricales), a new species from China revealed by morphology, and multilocus phylogenetic analysis, pp. 69-78 in Phytotaxa 545 (1) on pages 72-76, DOI: 10.11646/phytotaxa.545.1.5, http://zenodo.org/record/6520388