Megacoelomyces (type species: Megacoelomyces sanchezii), an ascomycete asexual morph infecting Myrcia fenzliana (Myrtaceae) from the Brazilian Cerrado, is described as a new genus in the Phaeosphaeriaceae (Pleosporales, Dothideomycetes, Ascomycota), based on multilocus phylogeny (three nuclear ribosomal DNA and two protein-coding genes) in addition to morphological (light and scanning electron microscopy) and ecological data