Mimimitoceras Korn, 1988

Korn, Dieter & Weyer, Dieter, 2023, The ammonoids from the Gattendorfia Limestone of Gattendorf (Devonian-Carboniferous boundary; Upper Franconia, Germany), European Journal of Taxonomy 883, pp. 1-61 : 8

Genus Mimimitoceras Korn, 1988

Type species

Mimimitoceras trizonatum Korn, 1988 ; original designation.

Diagnosis

Genus of the subfamily Prionoceratinae with discoidal to globular conchs; 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; Korn & Weyer 2023): Postprolobites varicosus Schindewolf, 1923 ; Mimimitoceras crestaverde Korn, 1992 ; Mimimitoceras hoennense Korn, 1993 ; Mimimitoceras perditum Korn & Weyer, 2023 .

North Africa ( Bockwinkel & Ebbighausen 2006; Korn & Weyer 2023): Mimimitoceras mina Korn & Weyer, 2023 .

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 1988). 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 .