On the phylogeny of Early Cardioceratidae (Ammonoidea) and Cadoceratinae from Central Russia at the Bathonian–Callovian boundary

Abstract

The phylogeny of the Middle Jurassic Cardioceratidae is reconstructed on the basis of a study of their shell morphology and analysis of their stratigraphic distribution. The phylogenetic lineage Cranocephalites → Arctocephalites → Arcticoceras → Paracadoceras is assigned to the subfamily Arctocephalitinae (Upper Bajocian–lowermost Callovian). The subfamily Cadoceratinae (Upper Bajocian–Callovian) also originating from Cranocephalites includes the phylogenetic lineage Greencephalites → Cadoceras → Longaeviceras; and lateral branches Chamoussetia and Platychamoussetia. The origin of the Early Callovian Eckhardites, also assigned to Cardioceratidae, is not established. The generic names Rondiceras and Cadochamoussetia are considered as junior synonyms of Cadoceras and Chamoussetia, respectively. The Early Callovian species Cadoceras bellabimba sp. nov. is described.