Comments: Application of the name Ascomycota to this clade, and the choice of this name rather than the synonyms Ascomycetes (class) and Ascomycotina (subphylum), follow the phylogeny-based classification of Hibbett et al. (2007), which has been adopted in Ainsworth & Bisby's Dictionary of the Fungi (Kirk et al., 2008) and the GenBank taxonomy (http://www.ncbi.nlm.nih.gov/guide/taxonomy). In rankbased classifications (e.g. Kirk et al. 2008, Spatafora et al. 2017), the clade Ascomycota is the largest phylum of Fungi. It is supported in molecular phylogenetic analyses (Lutzoni et al. 2004, James et al. 2006, Schoch et al. 2009) and comprises three mutually exclusive subclades (Carbone et al. 2017, Schoch et al. 2009, Spatafora et al. 2006). Taphrinomycotina is sister group to a well-supported clade comprising Saccharomycotina and Pezizomycotina. Pezizomycotina includes all ascoma-producing taxa with the exception of Neolectomycetes of Taphrinomycotina. The monophyly of Taphrinomycotina was not supported by early analyses of ribosomal data (reviewed in Sugiyama et al. 2006), but sampling of protein coding loci (RPB1, RPB2, and TEF) and mitochondrial DNA in multi-gene analyses provided support for its monophyly (James et al. 2006, Liu et al. 2008, Spatafora et al. 2006). Saccharomycotina (Riley et al. 2016, Shen et al. 2016) and Pezizomycotina (Carbone et al. 2017, Kumar et al. 2012, Schoch et al. 2009, Spatafora et al. 2006) are both well-supported clades. The sister group of Ascomycota is Basidiomycota (James et al. 2006). The fossil record of Ascomycota dates to at least the Devonian, with Paleopyrenomycites (Taylor et al. 2005), and the enigmatic Prototaxites taitii (Honegger et al. 2018) identified as part of the Rhynie Chert fossil fungi, but putative ascomycete fossils have been reported from the Silurian (Sherwood-Pike & Gray, 1985). Efforts to fit molecular phylogenies to the fossil record have estimated the origin of Ascomycota to be between 0.40 to 1.3 billion years before present (Heckman et al. 2001, Lücking et al. 2009, Taylor & Berbee 2006).