The other members of the Anatinae are the extinct moa-nalo, a young but highly apomorphic lineage derived from the dabbling ducks.

The classification as presented here more appropriately reflects the remaining uncertainty about the interrelationships of the major lineages of Anatidae (waterfowl).

[2] The dabbling duck group, of worldwide distribution, was delimited in a 1986 study[3] to include eight genera and some 50–60 living species.

[2] This group of ducks has been so named because its members feed mainly on vegetable matter by upending on the water surface, or grazing, and only rarely diving.

In addition, the genus Anas, as traditionally defined, is not monophyletic; several South American species belong to a distinct clade which would include the Tachyeres steamer-ducks.

[6] Because of its unique apomorphies (it seems to have had small eyes high and far back on its head), the placement of this anatid is likewise unresolved; only dabbling ducks and true geese are with certainty known to have colonized the Hawaiian archipelago.

Flightless or at least a poor flyer, it instead shows adaptations for wing-propelled diving, occupying a similar ecological niche to that of penguins and plotopterids.