Referring to the clavate ascospores of this fungus.

Thailand, That Phanom, Nakhon Phanom, on submerged decaying wood, 13 November 2018, D.F. Bao, B-161 (MFLU 19–2843, holotype), ex-type culture, MFLUCC 19–0496.

Saprobic on submerged decaying wood. Sexual morph: Ascomata 145–210 × 145–195 μm (x̄ = 175 × 169 μm, n = 10), immersed to semi-immersed, gregarious, scattered, erumpentia, depressed globose to conical with a flattened base, dark brown to black, as dark spots on host surface. Ostiole central, round to papillate, short, crest-like, dark brown. Peridium 28–47 μm wide, comprising several layers, pale brown to brown cells of textura anngularis. Hamathecium comprising 1.5–2.0 μm (n = 30) wide, numerous, branched, septate, hyaline, cellular pseudoparaphyses. Asci 110–148 × 20–27 μm (x̄ = 129 × 23 μm, n = 20), 8-spored, bitunicate, fissitunicate, cylindrical-clavate, rounded at apex, with a short pedicellate. Ascospores 48–51 × 7.5–9 μm (x̄ = 50.5 × 8.5 μm, n = 30), overlapping, 2–3-seriate, clavate, with round ends, straight, uniseptate, deeply constricted at septum, hyaline, with broad and short upper cells 16.6–18.9 × 7.8–9.0 μm (x̄ = 17.7 × 8.4 μm, n = 30), narrow and long lower cells 30–32.9 × 6.5–8.0 μm (x̄ = 31.5 × 7.3 μm, n = 30), tapering towards the end, guttulate, smooth, 2–4 equatorial appendages at the septum and surrounded by a fusiform gelatinous, sheath. Asexual morph：Undetermined.

Ascospores germinating on PDA within 24 hours. Colonies on MEA effuse, velvety, greyish-white to dark brown from above and below, reaching 2.5–3 cm diameter within 30 days at room temperature under natural light, composed of subhyaline to brown, septate, smooth hyphae.

Thailand, That Phanom, Nakhon Phanom, on submerged decaying wood, 13 November 2018, D.F. Bao, B160 (paratype: MFLU 19–2844; living culture, MFLUCC 19–0498); Thailand, That Phanom, Nakhon Phanom, on submerged decaying wood, 13 November 2018, D.F. Bao, B136 (paratype: MFLU 19–2845; living culture, MFLUCC 19–0495)

Tingoldiago clavata resembles the type species, T. graminicola in having bitunicate, cylindrical-clavate asci with a short pedicellate and clavate, hyaline, 1-septate, ascospores with broad upper cells, narrow lower cells. However, we can distinguish them by the size of ascomata and asci and the colour, septate and appendages of ascospores. Tingoldiago clavata has smaller ascomata (110–148 ×145–195 vs. 150–250 × 250–450 μm) and larger asci (110–148 × 20–27 vs. 87.5–122 × 18.25–25 μm). Moreover, ascopsores of T. clavata are hyaline, uniseptate, with 2–4 equatorial appendages at the septum, while ascopspores of T. graminicola are brown and 3-septate at maturity and lacking appendages at the septum. In addition, a comparison of the 491 nucleotides across the ITS gene region of T. clavata and T. graminicola reveals 25 base-pair differences and therefore provides further evidence to introduce T. clavata as a new species as recommended by Jeewon and Hyde (2016).