Abstract
Pleosporales, the largest order within Ascomycota, is globally distributed and exhibits remarkable host diversity. Fagaceae, a plant family of significant ecological importance in the Northern Hemisphere, harbors a wide array of fungal species. During an investigation of pleosporalean fungi associated with woody litter from Fagaceae plants, dead wood samples with fungal fruiting bodies were collected in Henan and Jiangxi provinces, China. In this study, we describe two novel species, Pseudothyridariella fagacearum and Phaeoseptum biyangense, and report a new host record for Byssosphaeria siamensis. These taxa are formally characterized using an integrative taxonomic approach, which combines detailed morphological characterization with maximum likelihood (ML) and Bayesian inference (BI) phylogenetic analyses of multi-locus sequence data (ITS, LSU, SSU, rpb2, and tef1-α). The newly designated species can be morphologically distinguished from other members of the respective genera based on the size of the asci and ascospores. This comprehensive study enhances our understanding of microfungi associated with Fagaceae, contributing to the knowledge of China's biodiversity.