N. Jb. Geol. Paläont. Abh. Stuttgart, www.schweizerbart.de E. Schweizerbart’sche Verlagsbuchhandlung, Stuttgart, Germany DOI: New finding of Cyclida (Crustacea) from Mississippian and not-cyclidan from Permian of Russia Eduard V. Mychko, Alexander S. Alekseev, Elena L. Zaytseva, Carrie E. Schweitzer, and Rodney M. Feldmann With 5 figures Abstract: A new genus and species of cyclidan Magnitocyclus struveae gen. et sp. nov., from the Mississippian of the Urals is described and illustrated. It is the frst reliable record of a cyclidan in the Upper Viséan – Lower Serpukhovian of Russia. Petschorocaris kozhimensis, from the Permian of the Pechora Coal Basin (Russia), is not a cyclidan but is apparently the mold of a patella-like gastropod shell. Key words: Crustacea, Cyclida, Carboniferous, Mississippian, Permian, Russia. 305/1 (2022), 75–85 July 2022 Article © 2022 10.1127/njgpa/2022/1077 0077-7749/2022/1077 $ 2.75 1. Introduction Cyclidans are enigmatic, extinct crustaceans that had a crab-like carapace, long before the origin of true crabs. The frst cyclidans appeared in the Early Car- boniferous, survived the Great Permian extinction, and existed until the end of the Late Cretaceous (Maas- trichtian). The specifc structure of the carapace, a pair of antennal structures, number of legs, markedly re- duced abdomen and a horseshoe-shaped array of gill flaments do not support cyclidans being assigned to a previously defned higher taxon (subclass or infra- class) of Crustacea. Therefore, like many previous au- thors, we consider cyclidans to be in the order Cyclida Schram, Vonk & Hof , 1997, within the superclass Multicrustacea Regier et al., 2010. The earliest recognition of cyclidans was in the frst half of the 19 th century. Currently, the order Cyclida includes 6 families, 27 genera and 53 species. Fossils of cyclidans are sporadic and rare, and there were no general studies up until recently. Interest in these ex- tinct crustaceans has erupted, a general morphology and terminology was developed to describe cyclidans (Feldmann & Schweitzer 2019), and then a detailed revision of Cyclida (Schweitzer et al. 2020) was con- ducted. Remains of cyclidans are known from Europe, Asia, North America, and Madagascar. In the terri- tory of Russia, specimens of cyclidans are very rare and confned to the Middle and Southern Urals. They are represented by Prolatcyclus kindzadza Mychko et al., 2019, from the Viséan of the Orenburg Region, Ambocyclus capidulum (Chernyshev , 1933) from the Serpukhovian of the Sverdlovsk Region, Uralocyclus miloradovitchi (Kramarenko, 1961) from the As- selian of the Chelyabinsk Region, and Skuinocyclus juliae Mychko & Alekseev , 2018 from the Asselian of the Bashkortostan. There are records in various works about other rare fndings of Russian cyclidans, but without details and descriptions (Mychko et al. 2019: 81). Therefore, any new discoveries of these fossils are extremely important for understanding their evolutionary history and paleobiogeography. eschweizerbart_xxx