The genus Atherina (Atheriniformes, Teleostei) includes five extant brackish and marine species that inhabit the eastern Atlantic, Mediterranean Sea, Black Sea, and Caspian Sea. Several fossil species are known from the Mediterranean and Paratethyan basins. Here we describe a new fossil species, Atherina atropatiensis sp. nov., from Upper Miocene deposits of the intramontane Tabriz Basin in NW Iran, based on well-preserved, articulated skeletons from the Lignite Beds at Baghmisheh-Marzdaran, near Tabriz. The new fossil species closely resembles the Recent A. boyeri, the only extant species of Atherina in the Caspian Sea, from which it can be distinguished by the different relative development of the ascending and alveolar processes of the premaxilla, and the mutual relationship between pleural ribs and dorsolateral process of the basipterygium. The systematic and Zoogeographic affinities of A. atropatiensis indicate that the Lignite Beds of the Tabriz Basin were deposited in a euryhaline environment and t...