Arius argentinus Dolgopol, 1941 Bachmannia is an extinct genus of ray-finned fish from the order of the catfishes (Siluriformes), containing a single species, B. chubutensis (syn.

[1] Fossils of the species, dated to the early Eocene, were found in the Laguna del Hunco site, a caldera in the Argentinean province of Chubut, which is filled with fine-grained, layered mudstones and sandstones interspersed with pyroclastic deposits.

[2] The genus was named by Mathilde Dolgopol de Sáez, in honor of the German physician and naturalist Franz Ewald Theodor Bachmann.

The Laguna del Hunco was located on the southern edge of the tropics, in a humid climate with a distinct maritime influence.

[2] A common feature (synapomorphy) of Bachmanniidae and Diplomystidae is a double, anterior articular head of the palatinum.