Racodium

Racodium is a monotypic fungal genus in the family Racodiaceae, which is itself the sole family of the order Racodiales. The genus contains a single species, Racodium rupestre, a distinctive filamentous lichen that forms dark, thread-like growths on rocks by closely enveloping filaments of the green algal genus Trentepohlia. The name has a complex taxonomic history, having been used for both this rock-dwelling lichen and an unrelated cellar fungus, until nomenclature experts formally conserved Racodium for the lichen genus in 2011. Modern DNA studies place this unusual lichen close to the Capnodiales, where it represents such a distinct evolutionary lineage that it has been assigned its own order and family.