Volhynian (Early Sarmatian s.l.) fishes from Tsurevsky, North Caucasus (Russia)

A new fish fauna is described from the late Middle Miocene (Volhynian; early Sarmatian sensu lato) of Tsurevsky, North Caucasus, Russia. Ten taxa belonging to nine families are described, of which two may be new (Micromesistius sp., Bothus sp.), but not formally described awaiting better-preserved material. The predominant faunal element is Sardinella sardinites, including more than 42% of all investigated specimens. The paleoecological analysis reveals a semienclosed marine environment not far from the coast, characterized by shallow depths and a soft bottom. The sedimentological features of the deposits and the preservation of the specimens suggest that periodic oxygen minima affected the bottom waters, causing repeated hypoxic events, probably related to the decay of organic matter previously accumulated in the basin. Paleoenvironmental considerations of fish faunas from several Paratethyan localities suggest that marine waters characterized by a little shift in chemical composition (high alkalinity) filled up the entire basin during the Sarmatian