Fragmentary remains of small dolphins from the Pinpa and Ericmas faunas of the fluvial-lacustrine Middle Miocene Namba Formation, Tarkarooloo Basin, Lake Frome area, represent an indeterminate genus and species of the extinct family Rhabdosteidae (= Eurhinodelphidae). They provide evidence of a marine connection of the Tarkarooloo Basin before or during the Middle Miocene and constitute the first record of rhabdosteids from Australia. Rhabdosteids have been recorded previously in the Southern Hemisphere only from Patagonia and, provisionally, New Zealand. Hitherto, rhabdosteids have not been reported from fluvial-lacustrine sediments.