Stiff-tailed ducks are part of the Oxyurinae subfamily of ducks.

Oxyura, stiff-tailed ducks (five living species)

New Zealand Stiff-tailed Duck.

Subfamily Oxyurinae: Stiff-tailed ducks and allies.

The White-headed Duck (Oxyura leucocephala) is a small stiff-tailed duck.

Biziura is a genus of stiff-tailed ducks endemic to Australasia and containing one living and one fossil species.

The extinct New Zealand Stiff-tailed Duck, Oxyura vantetsi, was named in his honour.

The New Zealand Stiff-tailed Duck presumably became extinct due to overhunting by the Māori in the 16th century.

The Musk Duck (Biziura lobata) is a highly aquatic, stiff-tailed duck native to southern Australia.

The Masked Duck (Nomonyx dominicus) is a tiny stiff-tailed duck ranging through the tropical Americas.

The specific name honours the late Australian ornithologist Gerard Frederick van Tets (1929-1995) who first recognized the relationship of this species with the stiff-tailed ducks in 1983.

The Blue-billed Duck (Oxyura australis) is a small Australian stiff-tailed duck, with both the male and female growing to a length of 40 cm (16 in).

As such, it is quite closely related to the stiff-tailed ducks proper, but as it seems not as closely as generally believed, with many similarities due to convergent evolution.

The Black-headed Duck (Heteronetta atricapilla) is a South American duck allied to the stiff-tailed ducks in the subfamily Oxyurinae of the family Anatidae.

The New Zealand Stiff-tailed Duck (Oxyura vantetsi) is an extinct duck species from New Zealand which is known only from subfossil remains.

The Ruddy Duck (Oxyura jamaicensis) is a duck from North America and the Andes Mountains of South America, one of the stiff-tailed ducks.

The New Zealand Musk Duck (Biziura delautouri ), also known as de Lautour's Duck, is an extinct stiff-tailed duck native to New Zealand.

It is distinct from all other ducks, but most closely related to the whistling ducks in the subfamily Dendrocygninae, though also showing some similarities to the stiff-tailed ducks in the subfamily Oxyurinae.

The New Zealand Stiff-tailed Duck was closely related to the Australian Blue-billed Duck (Oxyura australis) but its bones were about one tenth smaller than those of its Australian relative.

Overall much resembling a fairly typical diving duck, its plumage and other peculiarities give away that it is not a very close relative of these, but rather the product of convergent evolution in the ancestors of the stiff-tailed ducks.

Altogether however, the only thing that seems clear is that the musk ducks probably are not part of the stiff-tailed ducks in the strict sense but rather represent a not-too-distantly related lineage that is highly convergent as regards their hindlimb anatomy.

Their anatomy is more similar to Oxyura than to the two less derived genera, but still unique in many respects.

Stiff-tails: Oxyura.

New British species, corrections of nomenclature, etc. (Cynipidae, Ichneumonidae, Braconidae, and Oxyura).

For example, the African White-backed Duck (Thalassornis) also shows some similarities to Oxyura, but again, this may be yet another case of convergent evolution.

RUDDY DUCK Oxyura jamaicensis.

It is traditionally included with the stifftail subfamily Oxyurinae, but appears only distantly related to the genus Oxyura, and its peculiar apomorphies make it difficult to place.

WHITE-HEADED DUCK Oxyura leucocephala.

Europe's rarest duck, the white-headed Oxyura leucocephala, used to live throughout the Mediterranean region, but hunting and habitat destruction have wiped out most of the population since the beginning of the century.

ANATIDAE Oxyura maccoa (Maccoa Duck) Near Threatened (NT)

It is sometimes included with the latter in the genus Oxyura, but apparently the Masked Ducks of our time are the descendants of a missing link in the Oxyurinae evolution, having changed but little for millions of years.