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{{Short description|Tribe of birds}}
{{
| fossil_range = [[Late Oligocene]] to present
| image = Blue-billed-duck.jpg
| image_caption = [[Blue-billed duck]] (''Oxyura australis'')
| taxon =
| authority = [[William John Swainson|Swainson]], 1831
| subdivision_ranks = Genera
| subdivision =
''[[Oxyura]]''<br/>
''[[Nomonyx]]''<br/>
''[[Heteronetta]]''
}}
The '''
Their [[Morphology (biology)|habitus]] resembles a freshwater [[diving duck]], particularly when moving on dry land. Their legs are set far back, making them awkward walkers, so they rarely leave the water. When at rest, their tails are a notable difference
== Systematics ==
One mid-sized [[genus]] and two or three which are [[monotypic]] are described today:
{| class="wikitable"
* ''[[Black-headed duck|Heteronetta]]'' – black-headed duck▼
|-
! Image !! Genus !! Living Species
|-
|[[File:Heteronetta atricapilla blackheadedduck (cropped).jpg|250px]]|| ''[[Black-headed duck|Heteronetta]]'' {{au|Salvadori, 1866}}||
|-
|[[File:Nomonyx dominicus Pato enmascarado Masked Duck (10724525153).jpg|250px]]||''[[Masked duck|Nomonyx]]'' {{au|Ridgway, 1880}}||
*masked duck, ''Nomonyx dominicus''
|-
|[[File:White-headed duck - witkopeend - Oxyura leucocephala.jpg|250px]]||''[[Oxyura]]'' {{au|Bonaparte, 1828}} – stiff-tailed ducks||
*[[Blue-billed duck]], ''O. australis''
*{{extinct}}[[New Zealand stiff-tailed duck]], ''O. vantetsi''
*[[Ruddy duck]], ''O. jamaicensis''
*[[Andean duck]], ''O. ferruginea''
*[[White-headed duck]], ''O. leucocephala''
*[[Maccoa duck]], ''O. maccoa''
*[[Lake duck]], ''O. vittata''
|-
|}
The [[black-headed duck]] of ''Heteronetta'' is indisputably quite [[basal (evolution)|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 [[Morphology (biology)|habitus]] and pronounced [[sexual dimorphism]]; they are of uncertain position and decidedly aberrant. Their [[anatomy]] is more similar to ''[[Oxyura]]'' than to the two less derived genera, but still unique in many respects. [[mtDNA]] [[cytochrome b|cytochrome ''b'']] [[DNA sequence|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]].<ref name=Livezey/><ref name=Sraml/>
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 evolution|convergent]] as regards their hind limb [[anatomy]]. These two are probably part of a very ancient [[radiation (evolution)|radiation]] of [[Gondwana]]n (often [[Australia]]n) waterfowl, including such forms as the [[Cape Barren goose]] (''Cereopsis''), the [[coscoroba swan]] (''Coscoroba''), the [[freckled duck]] (''Stictonetta'') which once was placed in the Oxyurinae, or the [[pygmy geese]] (''Nettapus''), but the exact relationships between these lineages remains unresolved. 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.<ref name=Livezey/><ref name=Sraml/><ref name=McCracken/>
One [[fossil]] genus of
==References==
{{Reflist|refs=
<ref name=Livezey>{{cite journal|author=Livezey, Bradley C. |year=1986|title= A phylogenetic analysis of recent anseriform genera using morphological characters|journal=[[Auk (journal)|Auk]]|volume=103|issue=4|pages= 737–754|url=http://sora.unm.edu/sites/default/files/journals/auk/v103n04/p0737-p0754.pdf|jstor=4087184}}</ref>
<ref name=McCracken>{{cite journal|author1=McCracken, Kevin G.
<ref name=Sraml>{{cite journal|author1=Sraml, M. |author2=Christidis, L. |author3=Easteal, S. |author4=Horn, P. |author5=Collet, C. |
}}
==External links==
{{
{{Odontoanserae|B.}}
{{Taxonbar|from=Q33177705}}
▲[[Category:Oxyurinae| ]]
[[Category:Ducks]]
[[Category:Extant Chattian first appearances]]
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