Their unusual courtship displays involve drumming noises from inflatable throat sacs, head throwing, and erecting short crests.

One mid-sized genus and two or three which are monotypic are described today: The black-headed duck of Heteronetta is indisputably quite basal, looking more like a typical duck-like Anatidae with a short tail and normal bill.

The masked duck of Nomonyx has a more intermediate position; it probably diverged from the lineage leading to the main radiation some time after Heteronetta.

The musk ducks (Biziura), sometimes included in this group, are noted for their bizarre habitus and pronounced sexual dimorphism; they are of uncertain position and decidedly aberrant.

mtDNA cytochrome b sequence data suggest a closer relationship with the pink-eared ducks (Malacorhynchus) which if correct would represent one of the most drastic cases of divergent adaptation in the whole Anseriformes.