Abstract
A novel marine genus, Halobyssothecium (Lentitheciaceae), is introduced to accommodate Byssothecium obiones (= Halobyssothecium obiones) with evidence from phylogenetic analyses of concatenated LSU, SSU, ITS rDNA, and TEF1 sequence data. We could not locate any type material for this species and there is no molecular data available for the type of this species. Therefore, an epitype is designated for the precise delineation of this taxon. A detailed morphological description and DNA characterization based on LSU, SSU, ITS rDNA, and TEF1 sequence data are provided for the epitype, obtained from Spartina culms in Eastney, Langstone Harbour, Hampshire, UK.