A reassessment of the genus oligoneuriopsis crass, 1947 (Ephemeroptera, oligoneuriidae, oligoneuriellini)

The distinction between the two closely related genera Oligoneuriella Ulmer, 1924 and Oligoneuriopsis Crass, 1947 has been much debated. First described from South Africa, Oligoneuriopsis seemed to be a clearly defined genus. However, as the known distribution of the genus widened and knowledge on it expanded, species delimitation based on morphology became less clear due to overlap in several apparently defining morphological characters, especially in the nymphs. This work attempts to reassess Oligoneuriopsis morphology in the context of all currently known species. The type species, Oligoneuriopsis lawrencei Crass, 1947 is redescribed at the imaginal and nymphal stages and a neotype is designated. The putative nymph of Oligoneuriopsis dobbsi (Eaton, 1912) is described based on material collected around Mt Elgon (Kenya). The adults of Oligoneuriella orontensis Koch, 1980 are described for the first time and the species is transferred to the genus Oligoneuriopsis (Oligoneuriopsis orontensis comb. nov.). Egg structure is also described for the first time for the species Oligoneuriopsis skhounate and O. orontensis. Some biogeographical considerations are also given. It is likely that more species will still be discovered, especially in Africa.