It includes several genera of medium-sized to very large species, such as Icadyptes salasi, Palaeeudyptes marplesi, Anthropornis nordenskjoeldi, and Pachydyptes ponderosus.

In some taxa at least, the wing, while already having lost the avian feathering, had not yet transformed into the semi-rigid flipper found in modern penguin species: While the ulna and the radius were already flattened to increase propelling capacity, the elbow and wrist joints still retained a higher degree of flexibility than the more rigidly lockable structure found in modern genera.

The decline and eventual disappearance of this subfamily seem to be connected to increased competition as mammal groups such as cetaceans and pinnipeds became better adapted to a marine lifestyle in the Oligocene and Miocene.

Indeed, it was long assumed that all prehistoric penguins that cannot be assigned to extant genera belonged to the Palaeeudyptinae; this view is generally considered obsolete today.

It is likely that some of the unassigned New Zealand/Antarctican/Australian genera like Delphinornis, Marambiornis, and Mesetaornis do indeed belong into this subfamily, but it is just as probable that others, such as Duntroonornis and Korora, represent another, smaller and possibly somewhat more advanced lineage.