Stemonitis amphorocolumella (Stemonitidaceae, Myxomycetes), a new species from Western Siberia

A new Stemonitis species from Northern Asia is described and illustrated. The species was found in the Altai Territory, Russia. This new species clearly differs from previously known species by several morphological characters. The new species and four other species of the Stemonitis genus have the thickening and widening of the column apex—Stemonitis capillitionodosa, S. flavogenita, S. pseudoflavogenita, S. sichuanensis, which makes them a separate morphological group in the Stemonitis genus. However, four of the above listed species have warted and spinulose spore ornamentations, whereas the new species spore ornamentations are reticulate. The peridium of the new species is partially preserved in the form of a filmy collar at the base of the sporotheca, whereas the peridium of Stemonitis capillationodosa, S. flavogenita, S. pseudoflavogenita and S. sichuanensis is always fugacious. Scanning electron microfotographs of a new species of the Stemonitis genus and an updated original identification key for species of this genus around the world, which currently includes 23 taxa, are presented.