History of Science and Engineering Annotation << Back The History of Crassoid Mollusks of the Genus Didacna in the Caspian Sea Khlopkova M.V., Gasanova A.Sh., Guseynov K.M. The material is intended for readers interested in the evolutionary history of the Caspian Sea fauna. Traces of the ancient Paratethys Sea can be found in the modern Caspian, Black, and Aral seas, where they exist as a unique ecosystem and relict species. The article highlights that mollusks of the genus Didacna represent one of these species. Brackish-water bivalve Didacna mollusks are autochthons (permanent inhabitants) of the Caspian Sea and endemics of the entire Ponto-Caspian basin. To date, only one species of the crassa group has survived— Didacna baeri (Grimm, 1877). In conclusion, the author substantiates the importance of combining several scientific approaches to reconstruct the life of ancient mollusks in maximum detail. Keywords: Caspian Sea, Pleistocene, autochthons, evolutionary history of the genus Didacna. DOI: 10.25791/intstg.8.2026.1639 Pp. 48-52.