Initially the species was placed in the now defunct genus Colymbus by Shufeldt , it has since been reclassified into the genus Podiceps.
Paleobiology
The holotype femur was found at the John [DayFossil BedsNational Monument]. The age of P. oligoceanus is uncertain. Shufeldt tentatively assign the species of Oligocene age, while Brodkorb believed the species is of Early Miocene age. There are doubts, however, that P. oligoceanus could also be from the Pleistocene epoch due to how similar it is to modern grebes.