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

Several ammonoid specimens from the upper Valanginian (Lower Cretaceous) sedimentary succession of Hauteville-Lompnes, Department of Ain, eastern France, are assigned to the new genera and species Itierella melognensis n.gen., n.sp., and Paradicostella hautevillelompnesensis n.gen., n.sp. Specimens collected in the past were misidentified as Acanthodiscus Uhlig, 1905, and erroneously assigned to the lowermost part of the Hauterivian stage. The revision of the Marnes de Mélogne, along with the collection of a rich associated ammonite fauna, allows Itierella to be recognized as a latest Valanginian homeomorphic form of the genus Acanthodiscus, and Paradicostella as closely related to the genus Dicostella Busnardo, 1966. The Marnes de Mélogne are revised as mostly belonging to the upper Saynoceras verrucosum to Criosarasinella furcillata ammonite zones (uppermost Valanginian), while their uppermost metre is assigned to the Acanthodiscus radiatus Zone (lowermost Hauterivian).