| Oxyurini Temporal range:Late Oligocene to present | |
|---|---|
 | |
| Blue-billed duck (Oxyura australis) | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Anseriformes |
| Family: | Anatidae |
| Subfamily: | Anatinae |
| Tribe: | Oxyurini Swainson, 1831 |
| Genera | |
TheOxyurini are a tribe of theduck subfamily ofbirds, theAnatinae. It has been subject of considerable debate about its validity and circumscription. Some taxonomic authorities place the group in its own subfamily, theOxyurinae. Most of its members have long, stiff tail feathers which are erected when the bird is at rest, and relatively large, swollen bills. Though their relationships are still enigmatic, they appear to be closer to swans and true geese than to the typical ducks. The highest diversity is found in the warmer parts of theAmericas, but at least one species occurs in a major part of the world[clarification needed].
Theirhabitus resembles a freshwaterdiving 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, and in the water they often swim very deep-set. Their unusual courtship displays involve drumming noises from inflatable throat sacs, head throwing, and erecting shortcrests. Most display singly with a very elaborate and peculiar display, butmusk ducks congregate atleks and have a more limited display.
One mid-sizedgenus and two or three which aremonotypic are described today:
| Image | Genus | Living Species |
|---|---|---|
.jpg) | HeteronettaSalvadori, 1866 |
|
.jpg) | NomonyxRidgway, 1880 |
|
 | OxyuraBonaparte, 1828 – stiff-tailed ducks |
|
Theblack-headed duck ofHeteronetta is indisputably quitebasal, looking more like a typical duck-likeAnatidae with a short tail and normal bill. Themasked duck ofNomonyx has a more intermediate position; it probably diverged from the lineage leading to the main radiation some time afterHeteronetta.
The musk ducks (Biziura), sometimes included in this group, are noted for their bizarrehabitus and pronouncedsexual dimorphism; they are of uncertain position and decidedly aberrant. Theiranatomy is more similar toOxyura than to the two less derived genera, but still unique in many respects.mtDNAcytochromebsequence data suggest a closer relationship with the pink-eared ducks (Malacorhynchus) which if correct would represent one of the most drastic cases of divergentadaptation in the wholeAnseriformes.[1][2]
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 highlyconvergent as regards their hind limbanatomy. These two are probably part of a very ancientradiation ofGondwanan (oftenAustralian) waterfowl, including such forms as theCape Barren goose (Cereopsis), thecoscoroba swan (Coscoroba), thefreckled duck (Stictonetta) which once was placed in the Oxyurinae, or thepygmy geese (Nettapus), but the exact relationships between these lineages remains unresolved. For example, the Africanwhite-backed duck (Thalassornis) also shows some similarities toOxyura, but again, this may be yet another case of convergent evolution.[1][2][3]
Onefossil genus of Oxyurini,Tirarinetta from the Pliocene of Australia, and some prehistoric members of genera are still extant. Three enigmatic genera of waterfowl,Mionetta from theLate Oligocene toMiddle Miocene of central Europe andDunstanetta andManuherikia from theBathans Early/Middle Miocene of Otago, New Zealand, show some similarities to oxyurine ducks and judging frombiogeography, the latter two may plausibly be related. However,Manuherikia andMionetta are sometimes held to be Dendrocheninae adapted to diving, so closer towhistling ducks, a very ancient lineage of the Anatidae.
Media related toOxyurini at Wikimedia Commons
