Taxonomic validation of Ephoron yunnanensis Zhou, 2002 (nomen nudum) (Ephemeroptera, Polymitarcyidae).

Ephoron yunnanensis Zhou, 2002 is considered as a nomen nudum since only mentioned in an unpublished Ph.D. thesis and therefore not officially validated. This study validates the species based on specimens from China (Yunnan Province) and Thailand (Chiang Mai and Chiang Rai Provinces). The species is formally described here for the first time and illustrated. Our morphological evidence and COI data support its independent species status. Additionally, the egg of this species is described. Diagnostic characters, distributions, and keys for both the nymphal and imaginal stages of all known Thai Ephoron species are also provided.