Construction of the Phylogeny of Freshwater Mollusks by Paleozoogeographic Data Based on the Example of the Family Margaritiferidae (Bivalvia)

This article is devoted to the development of a consistent pattern of phylogenetic relationships between genera and species of the family Margaritiferidae (Bivalvia) based on paleozoogeographic data. At the same time, morphological and molecular genetic data were also taken into account. A scheme of supposed phylogeny has been constructed. According to this scheme, the first genus of the family, Tihkia , appeared at the beginning of the Middle Triassic in Gondwana (what would become Africa and India). The appearance of this genus was apparently facilitated by the formation of anadromous fishes of the order Acipenseriformes, which served as hosts for the larvae of marine mollusks of the order Trigoniida. This led to the colonization of freshwaters by mollusks and the formation of the family Margaritiferidae. In the Late Triassic, mollusks first spread to the west along the Gondwana coast and then to the east along the coast of Laurasia. During the colonization, the following currently extinct genera were successively formed: Proarcidopsis , Martinsoniconcha , and Shifangella . In the Jurassic, Shifangella gave rise to other two extinct genera, Mengyinaia and Palaeomargaritifera . Three modern genera are descended from different extinct genera: Pseudunio from Proarcidopsis , Cumberlandia from Shifangella , and Gibbosula from Palaeomargaritifera . The genera Pseudunio and Cumberlandia appeared in the Early Jurassic (western coast of the Tethys Ocean), Gibbosula in the Early Cretaceous (Asian coast of the Tethys Ocean), and Margaritifera in the Eocene from representatives of Pseudunio (the Pacific coast of North America). Although some of the assumptions of the proposed phylogeny are insufficiently substantiated, it is generally quite consistent with the currently available data.