Ustilago is a polyphyletic genus of smut fungi found mainly on Poaceae. The development of
a taxonomy that reflects phylogeny requires subdivision of Ustilago into smaller monophyletic genera.
Several separate systematic analyses have determined that Macalpinomyces mackinlayi, M. tubiformis,
Tolyposporella pachycarpa, Ustilago bouriquetii and U. maydis, occupy a unique phylogenetic position
within the Ustilaginaceae. A previously introduced monotypic generic name typified by U. maydis,
Mycosarcoma, is available to accommodate these species, which resolves one component of polyphyly
for Ustilago s. lat. in Ustilaginaceae. An emended description of Mycosarcoma is provided to reflect the
morphological synapomorphies of this monophyletic group. A specimen of Ustilago maydis that has had
its genome sequenced is designated as a neotype for this species. Taxonomic stability will further be
provided by a forthcoming proposal to conserve the name Uredo maydis over Lycoperdon zeae, which
has priority by date, in order to preserve the well-known epithet maydis.