Maasoglossum, a basal genus in Geoglossomycetes

• The earth tongue genus Maasoglossum was examined in depth.
• Maasoglossum was supported as a basal member of Geoglossomycetes.
• A new combination, Maasoglossum aseptatum, was made.
• The genus description of Maasoglossum was emended.
• Morphology of basal Geoglossomycetes suggests common ancestry between Geoglossomycetes and Leotiomycetes.

The genus Maasoglossum is examined using morphology, ecology, and molecular systematics of the internal transcribed spacer region and large subunit of the nuclear ribosomal RNA gene, all of which support the placement of Maasoglossum among the basal members of Geoglossomycetes. The morphology of the genus extends the range of ascocarp and ascospore development in Geoglossomycetes. The ecology and conservational significance of the genus is discussed, a nomenclatural transfer of Geoglossum aseptatum to Maasoglossum is made, and an emended description of Maasoglossum is provided.