Fitzroyomyces xishuangbannaensis R.F. Xu & Tibpromma, sp. nov. (Fig. 3) Index Fungorum Number: IF 559624; Facesoffungi Number: FOF 10811 Holotype: HKAS 122682 Etymology: The specific epithet “xishuangbannaensis” refers to Xishuangbanna, in Yunnan Province where the holotype was collected. Saprobic on dead branch of Hevea brasiliensis. Sexual morph: Apothecial 235–430 high μm, 200–520 diam μm (x̅ = 300 × 400 μm, n = 10), subglobose, unilocular, gregarious, immersed from the substrate, immersed at first and opening by entire pore at maturity. Hypothecium convex. Disc deeply cupulate, whitish to cream. Margins white. Hymenium hyaline, enclosed in a thick gelatinous matrix. Epithecium absent. Excipulum 20–55 μm composed of cells of textura intricata. Paraphyses 1–2 μm wide at the apex, numerous, filiform, septate, unbranched. Asci 160–180× 10–20 μm (x̅ = 173 × 13 μm, n = 11), 8-spored, unitunicate, long cylindrical, short sessile, rounded at the apex. Ascospores 90–180 × 2–4 μm (x̅ = 152 × 3 μm, n = 10), filiform, hyaline, multiseptate, up to 35-septa, finely guttulate when immature, not constricted at the septa and not easily break into different size. Asexual morph: Undetermined. Material examined: CHINA, Yunnan Province, Xishuangbanna, on a dead branch of Hevea brasiliensis Muell. Arg, 30 July 2021, Ruifang Xu, XSBNR–20, (HKAS 122682, holotype). Notes: The nucleotide base pair differences of ITS, LSU and mtSSU sequences are compared between our new species and members of Fitzroyomyces (Table 2). The new taxon was established based on the recommendations outlined by Jeewon & Hyde (2016). We also compared the morphology of our strain with Fit. cyperacearum, Fit. hyaloseptisporus, Fit. pandanicola and Fit. yunnanensis (Table. 3). The differences between Fit. xishuangbannaensis and Fit. cyperacearum are that the larger apothecia (235–430 × 200–520 μm vs. 201–260 × 210–310 μm), wider exciple (17–70 μm vs. 20–55 μm), narrower paraphyses (17–70 μm vs. 24–54 μm), longer asci (110–150 × 10–20 μm vs. 160– 180 × 10–20 μm), longer, and fusiform ascospore guttulate with more septation. Fitzroyomyces xishuangbannaensis differs from Fit. hyaloseptisporus in larger apothecia (235–430 × 200–520 μm vs. 140–200 × 150–200 μm), wider exciple (20–55 μm vs. 6–20 μm), smaller asci (160–180 × 10–20 μm vs. 165–200 × 10–25 μm) and ascospores (90– 180 × 2–4 μm vs. 150–200 × 3.5–6 μm), further, ascospores are fuliform with more septation in Fit. hyaloseptisporus whereas Fit. xishuangbannaensis possesses filiform, hyaline, multiseptate ascospores finely guttulate when immature (Wei et al. 2021). Fit. xishuangbannaensis and Fit. yunnanensis have the same geographical distribution in China (Lu et al. 2021) however, the two differ in several morphological characteristics such as Fit. yunnanensis has bigger apothecia, smaller asci, smaller ascospores and septation (Table 3). A key to species in Fitzroyomyces 1. Septation of ascospores less than 25..................................................................................................................... 2 1. Septation of ascospores more than 25 .................................................................................................................. 3 2a. Guttulate fusiform ascospores, textura intricata to textura angularis exciple......................................................... Fit. yunnanensis 2b. Eguttulate filiform ascospores, textura intricate exciple ...................................................................................... Fit. cyperacearum 3. Guttulate filiform ascospores ............................................................................................................................................................. 4 3. Eguttulate filiform ascospores.................................................................................................................................. Fit. pandanicola 4a. Ascospores commonly presenting 1–3 prominent constrictions (ascospores easily break into different size of fragments................ ........................................................................................................................................................................... Fit. hyaloseptisporus 4b. Ascospores not constricted at the septa and not easily break into different size......................................... Fit. xishuangbannaensis

Published as part of Xu, Ruifang, Thiyagaraja, Vinodhini, Dai, Dong-Qin, Karunarathna, Samantha C. & Tibpromma, Saowaluck, 2022, Additions to Fitzroyomyces (Stictidaceae, Ascomycota) from Yunnan Province, China, pp. 253-266 in Phytotaxa 548 (2) on page 260, DOI: 10.11646/phytotaxa.548.2.8, http://zenodo.org/record/6597872