Nubenocephalus nebraskensis n. gen., n. sp. (Apicomplexa: Actinocephalidae) is described from trophozoites, sporonts, gamonts, and oocysts collected from adult Argia bipunctulata (Odonata: Zygoptera). The new genus is distinguished from existing acanthosporine genera by elongate dodecahedral oocysts, without equatorial faces, that are hexagonal in equatorial cross section with equatorial and ... [Show full abstract] terminal spines. The epimerite is very broadly ovoid and truncated posteriorly with equatorial lobiform tumidi that are posteriorly bilobate and do not form hooks, spines, or digitiform processes. The epimerite is borne on a long, slender stalk. The new species is also reported from naiads ofArgia bipunctulata and adults and naiads of Enallagma civile (Odonata: Zygoptera).