RESUMO
Xylariomycetidae comprises extremely diverse taxa that are widespread on decaying wood worldwide. An investigation of the diversity of microfungi on oil tree plantations in Sichuan Province was conducted during 2020-2021. Twelve saprobic taxa representing five species were identified as members of Amphisphaeriales and Xylariales through morphological comparisons. Phylogenetic analyses of combined ITS, LSU, rpb2, tub2 and tef1 sequence data indicated a distinct clade formed by three strains within Xylariomycetidae, unrelated to any currently recognized families. Thus, a novel anthostomella-like genus, Bicellulospora, is proposed and treated as Xylariales genera incertae sedis. Bicellulospora is characterized by dark brown to black, immersed, subglobose ascomata with a clypeus, cylindrical asci, and hyaline to yellowish brown, inequilaterally ellipsoidal ascospores with a large upper cell and a dwarf lower cell. Two new species of Amphisphaeria, namely A. oleae and A. verniciae, are introduced based on multi-gene phylogenetic analyses (ITS, LSU, rpb2 and tub2) coupled with morphological characteristics. Amphisphaeria micheliae and Endocalyx ptychospermatis are reported as new host records.