Teleomorph.—Stromata effused-applanate on wood, elongated in coalescent strips, 15–70 mm long × 13–28 mm diam × 1.5–4.5 mm thick, soft-textured; surface Cinnamon (62), plane, with inconspicuous perithecial mounds; orange red granules immediately beneath the surface and between the perithecia, with yielding Orange (7) pigments in 10% KOH; subperithecial tissue grey brown, brownish black at base, 0.8–3.5 mm thick. Perithecia obovoid to tubular, 0.2–0.3 mm diam × 0.2–1.5 mm high. Ostioles umbilicate, inconspicuous. Asci with eight ascospores obliquely arranged in uniseriate manner, cylindrical, 130–195 μm total length, the spore-bearing parts 62.5–77.5 μm long × 5.5–7.5 μm broad, the stipes 40–125 μm long, with amyloid, discoid apical apparatus, bluing in Melzer’s iodine reagent, 1.0–1.5 μm high × 2.0–3.0 μm broad. Ascospores brown to dark brown, unicellular, ellipsoid-inequilateral, with narrowly rounded ends, smooth, 9.8–11.8 × 5.0–6.0 μm (M = 10.9 × 5.4 μm, n = 30), with straight germ slit slightly less than spore-length, inconspicuous; perispore dehiscent in 10% KOH, with inconspicuous coil-like ornamentation; epispore smooth.

Specimen examined.— CHINA. Yunnan Province, Xishuangbanna Dai Autonomous Prefecture, Mengla, Xishuangbanna tropical rainforest, Wangtian Tree scenic area, on dead decorticated dicotylous trunk in tropical rainforest, 19 October 2013, Ma Hai X., 215(FCATAS479).

Remarks.— Hypoxylon polyporoideum was originally described by Coock (1883) on bark and wood from Africa. This species was once treated by Miller (1961) and Ju & Rogers (1996) as a synonym of H. crocopeplum Berk. & M. A. Curtis. Hsieh et al. (2005) separated H. polyporoideum from H. crocopeplum based on a combination of morphological and phylogenetic (β- tubulin and α- actin) data. Hsieh et al. (2005) noted that H. polyporoideum differs from H. crocopeplum in having thicker stromata with tubular to long tubular perithecia and conspicuous black basal tissue beneath the perithecial layer morphologically. The Chinese material from Yunnan has thick stromata [1.5–4.5 vs. 0.5–1mm (Ma et al. 2013)], tubular perithecia, and brownish black tissue beneath the perithecial layer. The Chinese collection matches well the description from Hsieh et al. (2005) in morphology, and the phylogenetic analyses of ITS rDNA and β- tubulin sequences confirm that it is conspecific with H.polyporoideum (Hsieh et al. 2005). Phylogenetically H. polyporoideum is closely related to one collection of Hypoxylon cinnabarinum (Henn.) Y.M. Ju & J.D. Rogers (JDR43) on wood from Mexico, but the later has nearly equilateral ascospores, larger, 9.5–14 × 5.0–7.5 μm, perispore indehiscent in 10% KOH, dehiscent infrequently, smooth.