Uncobasidium luteolum is a species of crust fungus in the family Meruliaceae, and the type species of genus Uncobasidium. The holotype was collected in ÃÂvre Dividal National Park, in MÃÂ¥lselv Municipality (Norway), where it was growing on Salix. The fungus has a monomitic hyphal system, with individual hyphae measuring 2.5âÂÂ4 üm and having a clamp connection and oily refractive contents. The basidia are four-sterigmate, measure 30âÂÂ50 by 8 üm, and feature a hook-shaped protuberance. Its spores are ellipsoid to in shape, measuring 9 by 6 üm. Uncobasidium roseocremeum, found in South America, differs microscopically from U. luteolum in its larger, spherical spores, and the presence of encrusted hyphidia.