Sordariomycetes is one of the largest classes of Ascomycota that comprises a highly diverse range of fungi mainly characterized by perithecial ascomata and inoperculate unitunicate asci. Freshwater Sordariomycetes play an important role in ecosystems and some of them have the potential to produce bioactive compounds. This study documents and reviews the freshwater Sordariomycetes, which is one of the largest and important groups of fungi in aquatic habitats. Based on evidence from DNA sequence data and morphology, we introduce a new order Distoseptisporales, two new families, viz. Ceratosphaeriaceae and Triadelphiaceae, three new genera, viz. Aquafiliformis, Dematiosporium and Neospadicoides, 47 new species, viz. Acrodictys fluminicola, Aquafiliformis lignicola, Aquapteridospora fusiformis, Arthrinium aquaticum, Ascosacculus fusiformis, Atractospora aquatica, Barbatosphaeria lignicola, Ceratosphaeria aquatica, C. lignicola, Chaetosphaeria aquatica, Ch. catenulata, Ch. guttulata, Ch. submersa, Codinaea yunnanensis, Conioscypha aquatica, C. submersa, Cordana aquatica, C. lignicola, Cosmospora aquatica, Cylindrotrichum submersum, Dematiosporium aquaticum, Dictyochaeta cangshanensis, D. ellipsoidea, D. lignicola, D. submersa, Distoseptispora appendiculata, D. lignicola, D. neorostrata, D. obclavata, Hypoxylon lignicola, Lepteutypa aquatica, Myrmecridium aquaticum, Neospadicoides aquatica, N. lignicola, N. yunnanensis, Ophioceras submersum, Peroneutypa lignicola, Phaeoisaria filiformis, Pseudostanjehughesia lignicola, Rhodoveronaea aquatica, Seiridium aquaticum, Sporidesmiella aquatica, Sporidesmium lageniforme, S. lignicola, Tainosphaeria lunata, T. obclavata, Wongia aquatica, two new combinations, viz. Acrodictys aquatica, Cylindrotrichum aquaticum, and 9 new records, viz. Chaetomium globosum, Chaetosphaeria cubensis, Ch. myriocarpa, Cordana abramovii, Co. terrestris, Cuspidatispora xiphiago, Sporidesmiella hyalosperma, Stachybotrys chartarum,S. chlorohalonata. A comprehensive classification of the freshwater Sordariomycetes is presented based on updated literature. Phylogenetic inferences based on DNA sequence analyses of a combined LSU, SSU, RPB2 and TEF1α dataset comprising species of freshwater Sordariomycetes are provided. Detailed information including their habitats distribution, diversity, holotype, specimens collected and classification are provided.
