Neogobius bathybius is a species of goby endemic to the Caspian Sea, where it occurs in depths down to . It is strictly confined to the brackish-water basin and does not enter fresh waters. It can grow up to a length of TL.
The species was transferred to the genus Ponticola from Neogobius on the basis of relationship revealed in molecular investigations.Neilson M.E., Stepien C.A. (2009) Escape from the Ponto-Caspian: Evolution and biogeography of an endemic goby species flock (Benthophilinae: Gobiidae: Teleostei). Molecular Phylogenetics and Evolution, 52(1): 84-102. On the other hand, recent molecular studies have proven that this species belongs entirely to the genus Neogobius.
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