On the System and Phylogeny of the Beyrichitidae (Ammonoidea, Middle Triassic)

The history of the establishment of the family Beyrichitidae (Ammonoidea) and the opinions of various authors on its systematics are discussed. The morphological characteristics, composition, and distribution of beyrichitids are discussed; the family status of this group of Middle Triassic ammonoids is substantiated. A phylogenetic analysis of the ammonoids of the family Beyrichitidae is carried out, and two lineages in the evolution of the Boreal Late Anisian beyrichitids, recognized based on study of morphogenesis of the main structures of shells and analysis of chrono- and geochorological data are considered. A new subfamily Frechitinae subfam. nov. is established within Beyrichitidae.