Basidiomata pileo-stipitate, small to medium-sized (Fig. 1). Pileus (1.5–)2.0–2.5 cm in diameter, convex when young, becoming plano-depressed with age; margin deflexed to uplifted, surface finely tomentose, dull and dry, at first brown (7E4) to greyish-brown (8E3–8F4), becoming paler (8D3) near the margin with age; context 3–5 mm thick halfway to the margin, soft and fleshy, off-white, slightly browning on exposure. Stipe central, cylindrical, (3.4–)4.9–6.5 cm × 0.6–1.3 cm, surface even, dull and dry, scabrous, covered with granular squamules (dotted-verrucose), brownish-grey (7E2–8E2) when young to reddish-brown (8E5) to dark brown (8F5) with age, no colour change when bruised, basal mycelium off-white; context solid, fleshy, off-white, reddish-brown to dark brown near the stipe base (8F7) and in worm wounds, slightly browning on exposure. Hymenophore tubulate, subventricose, adnexed, slightly depressed around apex of the stipe, greyish-orange to brownish-orange when bruised. Tubes 3–6 mm long halfway to the margin, off-white, easily separable from one another. Pores ≤ 0.5 mm wide at mid-radius, regularly arranged, angular, off-white, turning brown to dark brown (8E5–8F5) when bruised. Odour fungoid. Taste bitter. Spore print not obtained.

Basidiospores (6.7–)7.5–10–11.7(–11.8) × (3.1–)3.5–4.7–5.8(–5.9) µm (n = 50) Q = (1.7–) 1.79–2.15–2.5 (–2.61), ellipsoid in central view, oblong to subcylindrical in side view, smooth under light microscope, yellowish to brownish in KOH (Fig. 2). Basidia 4-spored, (27–)27–37.4–54(–54) × (9–)9–12.3–19(–19) µm, clavate, yellowish to brownish in KOH, sterigmata up to 3 µm long. Cheilocystidia (19–)19.3–25.5–33(–35) × (4–)4.1–6–8.2(–8.5) µm, frequent, fusiform, thin-walled, yellowish to brownish hyaline in KOH and NH₄OH. Pleurocystidia (40­–)41–53–69(–70) × (8–)7.4–12–16.6(–17) µm, thin-walled, fusiform to broadly fusiform with a long pedicel and sharp apex, occasionally containing yellowish inclusions, yellowish to brownish hyaline in KOH and NH₄OH. Hymenophoral trama boletoid, elements smooth, cylindrical, hyaline, 5–10 µm wide. Pileipellis a trichodermium, hyphae terminations with 3–4 cells that are 5–11 µm wide and terminal cells 31–48 µm × 6–10 µm, colourless to slightly brownish in KOH. Pileus trama composed of interwoven hyaline hyphae 5–9 µm wide. Stipitipellis a disrupted hymeniderm with hyphae 3.7–7.4 µm wide, colourless to slightly brownish in KOH and caulocystidia (24–)24.5–35–47(–48) × (9–)9.2–12.4–16.9(–17) µm, thin-walled, clavate to broadly clavate with a sharp apex, yellowish to brownish hyaline in KOH and NH₄OH. Stipe trama composed of cylindrical, hyaline, interwoven hyphae 3.7–7.4 µm wide. Clamp connections absent.

This species is distinguished from Tylocinumgriseolum by its greyish-brown colour, greyish-orange to brownish-orange colour change in the hymenophore when bruised, smaller pores (≤ 0.5 mm) and longer tubes (up to 6 mm long). Additionally, the basidiospores are shorter and narrower compared to T.griseolum and the basidia are slightly longer and broader. Furthermore, the pleurocystidia of Tylocinumbrevisporum are longer than its cheilocystidia.

Epithet “brevisporum”; from the Latin words brevi (short) and sporae (spores), referring to the shorter spores of this species compared to Tylocinumgriseolum.

Thus far known only from northern Thailand.

Solitary, in tropical forest dominated by Dipterocarpaceae (Dipterocarpus spp. and Shorea spp.), with some Fagaceae (Quercus spp., Lithocarpus spp. and Castanopsiscalathiformis).

Morphologically, Tylocinumbrevisporum is similar to Tylocinumgriseolum, with which it shares the overall grey colour of the basidiomata and dark scabrous stipe surface. However, Tylocinumbrevisporum is more brownish as compared to the grey Tylocinumgriseolum. In addition, Wu et al. (2016) mentioned no discolouration in the context of Tylocinumgriseolum. The context of Tylocinumbrevisporum becomes slightly brown when bruised. The hymenophore of T.brevisporum changes to greyish-orange to brownish-orange when bruised as compared to the unchanging hymenophore of T.griseolum. Moreover, T.griseolum has relatively larger pores (up to 1.5 mm) than that of T.brevisporum (< 0.5 mm). The tubes in T.griseolum are also shorter than those of T.brevisporum.

The basidiospores of Tylocinumbrevisporum [(6.7–)7.5–10–11.7(–11.8) × (3.1–)3.5–4.7–5.8(–5.9) µm, Q = (1.7–)1.79–2.15–2.5(–2.61)] are shorter and narrower than those of Tylocinumgriseolum [(11)12.0–14.5(16) × 4.5–5.5 µm Q = 2.60–3.22] from China. The basidia of T.brevisporum [(27–)27–37.4–54(–54) × (9–)9–12.3–19(–19) µm] are also slightly longer and broader than T.griseolum [30–45 × 10–12 µm]. Wu et al. (2016) reported that, for T.griseolum, the pleurocystidia and cheilocystidia are similarly-sized. In T.brevisporum, the pleurocystidia are longer than the cheilocystidia. Phylogenetically, T.brevisporum clusters with T.griseolum, together forming a well-supported clade (MLB/BPP = 93/1.00) i.e. the genus Tylocinum.