The Late Pleistocene mollusk fauna of Selitrennoye (Astrakhan province, Russia): A natural baseline for endemic Caspian Sea faunas

The native Caspian Sea fauna underwent severe changes since the early 20th century, mostly due to anthropogenic activities. However, the nature, magnitude and rate of biodiversity change can only be assessed by comparison with natural baseline settings. A mostly in-situ mollusk fauna retrieved from Late Pleistocene (Hyrcanian, 107 ± 7 ka) deposits at Selitrennoye (Astrakhan province, Russia) provides a snapshot of a natural Caspian assemblage. In total, 24 gastropod and 13 bivalve species were identified. The fauna is predominantly endemic/native (94% in species numbers and 99% in abundance) and is dominated by three families (Cardiidae, Dreissenidae and Hydrobiidae). The Selitrennoye assemblage is a natural baseline of a pre-invasive Caspian Sea fauna living in a shallow (15–25 m), lower mesohaline (5–8 psu) open lake environment. The species-rich Selitrennoye fauna contrasts with the largely depleted and invasive-dominated fauna that currently occupies similar habitats in the Caspian Sea and underlines the magnitude of the current biodiversity crisis. action: H2020-MSCA-ITN-2014, acronym: PRIDE, grant agreement No: 642973