The holotype skull was figured in 1988 by R. E. Fordyce and Australodelphis mirus first appeared as a nomen nudum in E. H. Colbert's 1991 "Mesozoic and Cainozoic tetrapod fossils from Antarctica".

[1] All known specimens of Australodelphis were recovered from sediments of the Sørsdal Formation which outcrops at Marine Plain about 8 km south of Davis Station in the Vestfold Hills of East Antarctica.

The fossils are found in massive to poorly bedded muddy siltstone, dated at 4.5 to 4.1 million years old, placing the sediments in the Early Pliocene.

In their discussion of the species Archaeoziphius microglenoideus, the describing authors O. Lambert and S. Louwye note the distinct similarities between ziphiids but reaffirm the placement of Australodelphis.

[6] Australodelphis facial structure indicates a probable feeding style similar to the ziphiid whales, consisting of a rapid opening of the mouth to produce suction for capturing soft bodied prey.

[1] The structure of the nasal area indicates Australodelphis was likely to have enlarged nasiofacial muscles similar to Mesoplodon and indicate a possible ability to generate high-frequency sounds used in echolocation.