The ammonoids from the Gattendorfia Limestone of Oberrödinghausen (Early Carboniferous; Rhenish Mountains, Germany) Author Korn, Dieter 286CA4F3-7EBC-4AEF-A66A-B2508D001367 Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstrasse 43, 10115 Berlin, Germany. dieter.korn@mfn.berlin Author Weyer, Dieter A09A1738-C70E-4F22-A069-8B7DB4A1753D Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstrasse 43, 10115 Berlin, Germany. dieter.weyer@t-online.de text European Journal of Taxonomy 2023 2023-07-19 882 1 230 http://dx.doi.org/10.5852/ejt.2023.882.2177 journal article 58033 10.5852/ejt.2023.882.2177 57d1d191-2bf5-4229-a0f5-9ab472a114a6 2118-9773 8177581 67C909E4-C700-4F8D-B8CE-5FD9B2C5D549 Genus Mimimitoceras Korn, 1988 Type species Mimimitoceras trizonatum Korn, 1988 ; original designation. Diagnosis Genus of the subfamily Prionoceratinae with a discoidal to globular conch; umbilicus in the early juvenile stage slightly opened in most of the species and usually rapidly closing during the early whorls. External lobe usually V-shaped in globular species and lanceolate in discoidal species. Shell constrictions accompanied by an apertural shell bulge in the early and middle growth stage, internal shell thickenings usually cause deep steinkern constrictions throughout ontogeny. Included species Species lists including the Devonian species of the genus were published several times (Korn 1994; Korn & Klug 2002 ; Korn et al. 2015). The following Carboniferous species of Mimimitoceras are known from: Central Europe ( Schindewolf 1923 ; Korn 1992b , 1993): Postprolobites varicosus Schindewolf, 1923 ; Mimimitoceras crestaverde Korn, 1992 ; Mimimitoceras hoennense Korn, 1993 ; Mimimitoceras perditum sp. nov. North Africa ( Bockwinkel & Ebbighausen 2006 ): Mimimitoceras mina sp. nov. Remarks Mimimitoceras was revised with the description of Devonian North African material by Korn et al. (2015). The genus occurs in late Famennian ammonoid assemblages with numerous species; only two species are known so far from the basal Carboniferous Hangenberg Limestone of the Rhenish Mountains. Mimimitoceras is easily distinguished from the other genera of the subfamily Prionoceratinae by the presence of a bulging radial ridge in front of the shell constrictions ( Korn 1988c ). This bulge is usually not present throughout ontogeny; the shell constrictions may disappear in the adult stage. In some stratigraphically older species, such as M. lineare ( Münster, 1839 ) from the Late Famennian Clymenia laevigata Zone , they may be restricted to the juvenile stage. Based on this very minor variation, which rather describes a difference between species, Becker (1996) proposed the genus Rectimitoceras .