The order Jahnulales comprises freshwater, lignicolous ascomycetes within the class Dothideomycetes, subclass Pleosporomycetidae. Characterized by stalked or sessile, dimorphic ascomata, these fungi possess hyphal stalk cells approximately 40 µm in width. Their ascospores are typically one-septate and may be enveloped in gelatinous sheaths or bear apical appendages. Ecologically, Jahnulales species are commonly found on decaying submerged wood in freshwater habitats. The order includes two recognized families: Aliquandostipitaceae and Manglicolaceae. Phylogenetically, Jahnulales is closely related to other orders such as Dothideales, Patellariales, and Pleosporales.