Middle Holocene Herpetofauna and Paleogeographic Conditions Based on Fossil Remains from Medvezhiy Klyk Cave (Lozovy Ridge, Southern Sikhote-Alin, Primorsky Krai, Russia)

The study was based on material from the Medvezhiy Klyk Cave, located in the Southern Sikhote-Alin range in the Russian Far East. The aim of this research was to assess the taxonomic composition and changes in the species diversity of the Southern Primorye herpetofauna over geological time in response to environmental changes. In the fifth layer of sedimentary deposits in Medvezhiy Klyk Cave (horizons 15–11), corresponding to the Middle Holocene, remains of sixteen extant species of amphibians and squamate reptiles were identified: Bombina orientalis, Bufo sachalinensis, Dryophytes japonicus, Rana amurensis, R. dybowskii, Pelophylax nigromaculatus, Takydromus amurensis, T. wolteri, Zootoca vivipara, Elaphe dione, E. schrenckii, Lycodon rufozonatus, Hebius vibakari, Rhabdophis lateralis, Gloydius intermedius, and G. ussuriensis. Salamandrella sp. was identified only to the genus level due to difficulties in distinguishing species within this genus based on the preserved skeletal elements. Additionally, among the snake remains, some bones could not be assigned to any species in the comparative osteological collection. These remains are classified as Lycodon sp. and Serpentes gen. et sp. indet. They most likely also belong to extant species that currently inhabit regions south of the Russian border. The faunal assemblages of amphibians and reptiles indicate that forest vegetation predominated around the cave during the Middle Holocene, with the most extensive forest cover occurring during the accumulation of horizon 14. This period was also the most favorable for thermophilic and moisture-dependent species, including those whose current ranges lie further south. The climate throughout the deposition of the fifth layer is reconstructed as warmer and more humid than present-day conditions, consistent with other Middle Holocene climate reconstructions. Only horizon 11 corresponds to a relative climatic cooling.