Ascomycota, the most speciose phylum of fungi, is a complex entity, comprising three diverse; subphyla: Pezizomycotina, Saccharomycotina, and Taphrinomycotina. The largest and most diverse; subphylum, Pezizomycotina, is a rich tapestry of 16 classes and 171 orders. Saccharomycotina, the; second largest subphylum, is a diverse collection of seven classes and 12 orders, while; Taphrinomycotina, the smallest, is a unique assembly of six classes and six orders. Over the past; decade, numerous taxonomic studies have focused on the generic, family, and class classifications of; Ascomycota. These efforts, well-documented across various databases, are crucial for a; comprehensive understanding of the classification. However, the study of taxonomy at the ordinal; level, a crucial tier in the taxonomic hierarchy, has been largely overlooked. In a global collaboration; with mycologists and lichenologists, this study presents the first comprehensive information on the; orders within Pezizomycotina and Taphrinomycotina. The recent taxonomic classification of; Saccharomycotina has led to the exclusion of this subphylum from the present study, as an immediate; revision is not necessary. Each order is thoroughly discussed, highlighting its historical significance,; current status, key identification characteristics, evolutionary relationships, ecological and economic; roles, future recommendations, and updated family-level classification. Teaching diagrams for the; life cycles of several orders, viz. Asterinales, Helotiales, Hypocreales, Laboulbeniales, Meliolales,; Mycosphaerellales, Ophiostomatales, Pezizales, Pleosporales, Phyllachorales, Rhytismatales,; Sordariales, Venturiales, Xylariales (Pezizomycotina) and Pneumocystidales,; Schizosaccharomycetales and Taphrinales (Taphrinomycotina) are provided. Each diagram is; 540; explained with a representative genus/genera of their sexual and asexual cycles of each order. Within; Pezizomycotina, Dothideomycetes contains the highest number of orders, with 57, followed by; Sordariomycetes (52 orders), Lecanoromycetes (21 orders), Eurotiomycetes and Leotiomycetes (12; orders each), Laboulbeniomycetes (3 orders), and Arthoniomycetes and Xylonomycetes (2 orders; each). Candelariomycetes, Coniocybomycetes, Geoglossomycetes, Lichinomycetes, Orbiliomycetes,; Pezizomycetes, Sareomycetes, and Xylobotryomycetes each contain a single order, while; Thelocarpales and Vezdaeales are treated as incertae sedis within Pezizomycotina. Notably, the; classes Candelariomycetes, Coniocybomycetes, Geoglossomycetes, Sareomycetes, and; Xylonomycetes, all recently grouped under Lichinomycetes, are treated as separate classes based on; phylogenetic analysis and current literature. Within Lecanoromycetes, the synonymization of; Sporastatiales with Rhizocarpales and Sarrameanales with Schaereriales is not supported in the; phylogenetic analysis. These orders are retained separately, and the justifications are provided under; each section as well as in the discussion. Within Leotiomycetes, the order Medeolariales, which was; once considered part of Helotiales, is treated as a distinct order based on phylogenetic evidence. The; classification of Medeolariales may change as more data becomes available from different gene; regions. Lahmiales (Leotiomycetes) is not included in the phylogenetic analysis due to a lack of; molecular data. Sareomycetes and Xylonomycetes are treated as separate classes. Spathulospora; mixed with Lulworthiales and the inclusion of Spathulosporales within Lulworthiomycetidae is; supported and extant molecular sampling is important to resolve the phylogenetic boundaries of; members of this subclass. The majority of the classes of Pezizomycotina and Taphrinomycotina; formed monophyletic clades in the phylogenetic analysis conducted based on SSU, LSU, 5.8S, TEF; and RPB2 sequence data. However, Arthoniomycetes nested with the basal lineage of; Dothideomycetes and formed a monophyletic clade also known as the superclass, Dothideomyceta.; In Taphrinomycotina, a single order is accepted within each class.
