Untangling horsehair fungi in Australia: Marasmius crinis-equi (Marasmiaceae) and related taxa

Abstract Fungi with prominent hairlike rhizomorphs, aerial habit, sparse small sporophores, and usually saprotrophic biology are commonly known as ‘horsehair or spider fungi’. The earliest descriptions of them, from the mid-late 1800s, were published from Australian material under the names Marasmius crinis-equi and M. equicrinis . For the original ‘horsehair fungus’, we review this early historical material, briefly explore the changes in the species concept over time, and investigate the nomenclatural tangle of potentially competing names. Our analysis of morphological and molecular data for over 60 collections across eastern Australia shows that material labelled as M. crinis-equi forms part of a complex of at least three closely related species and that this name has been misapplied both within Australia and internationally. An epitype is nominated for an updated concept of M. crinis-equi , and the closely related taxa, M. tropicus sp. nov . and M. kabakada sp. nov . , are described. Two more distantly related Australian taxa to which the name M. crinis-equi has been misapplied, M. perumbilicatus sp. nov . and M. argillaceus sp. nov., are also described to further stabilise the concept of the authentic horsehair fungus M. crinis-equi.