Itierella melognensis n.gen., n.sp., and Paradicostella hautevillelompnesensis n.gen., n.sp. (Ammonoidea, Neocomitidae, Neocomitinae),

two new upper Valanginian trituberculated ammonoids from the Jura Mountains, eastern France

Abstract

Several specimens of ammonoids from the upper Valanginian sedimentary series (Lower Cretaceous) of Hauteville-Lompnes, Department of Ain, eastern France, are assigned to the new genera and species Acanthomorphites melognensis nov. n. gen. sp. and Paradicostella hautevillelompnensis nov. n. gen. sp. Specimens collected in the past were misidentified as Acanthodiscus Uhlig, 1905 and erroneously assigned to the lowermost Hauterivian stage. The revision of the Marnes de Mélogne and the harvesting of a rich associated ammonite fauna allows to assign Acanthomorphites to a latest Valanginian homeomorphic form similar to the genus Acanthodiscus, and Paradicostella close to the genus Dicostella Busnardo, 1966. The age of the Marnes de Mélogne is revised as uppermost Valanginian Neocomites peregrinus and Criosarasinella furcillata ammonite zones, while the uppermost metre can be attributed to the lowermost Hauterivian Acanthodiscus radiatus Zone.