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THE DUCK-CHICKEN THING



Sorry this post is a bit late - Matt posted the original on 
Thanksgiving - but what the hell. Taking issue with the generally 
agreed upon close affinity between anseriforms and galliforms, Matt 
wrote...

> [Anseriforms are] not related to galliforms in a close relationship. 
> To all who doubt, read Olson and Feduccia, 1980.  

Olson and Feduccia have, both together (Olson and Feduccia 1980a, 
1980b), and apart (Olson 1985, Feduccia 1996), argued strongly that 
there is no 'duck-chicken relationship' and that anseriforms are 
related to waders and flamingos, and that galliforms are of a totally 
unknown phylogenetic position. 

Molecular data, virtually without exception, groups galliforms and
anseriforms together as a clade that is the sister-group to all other
neornithines: Sibley and Ahlquist (1992) called this clade
Galloanserae. This evidence must be overturned or ignored if you are 
to reject galliform-anseriform affinity, and indeed in his 1985 
review Storrs Olson openly expressed the view that, if this is what 
the DNA data reveals, it must be wrong!

Cracraft, who has supported a galliform-anseriform affinity and has 
been severely critical of Feduccia and Olson's arguments to the 
contrary, points out in many of his texts that, just because a 
morphology 'looks different', it cannot be disregarded if the 
evidence indicates it to be a shared derived state. Most often, 
this is the reason Olson and Feduccia provide in their disagreement 
with the galliform-anseriform link. Matt's reasons in his 
Thanksgiving post were the same (shame on you Matt!:)) -  i.e., 
character X looks different, and therefore does not support affinity. 
Galliforms and anseriforms uniquely share some special cranial 
characters not seen in other birds (an unusual retroarticular process 
being the best known) - features that indicate that they are each 
others closest relatives, even though these structures do differ in 
the details. 

1997 was a particularly interesting year for this issue, as two big 
papers were published concerning it. What is important is that both 
found no support for Olson and Feduccia's theory about _Presbyornis_ 
being a duck-flamingo-shorebird mosaic: it is clearly an anseriform, 
and a close relative of ducks (anatids). Livezy (1997) found that, 
especially in the crania, all evidence indicated a 
galliform-anseriform clade, which he called Galloanserimorphae. 
Screamers and _Anseranas_, the magpie goose, truly were intermediates 
between more specialized galliforms and anseriforms, not just in 
osteology, but in soft tissues, pigmentation patterns, life histories 
and behaviour. Ericson (1997) (published in the same journal as 
Livezey's paper) relied rather more heavily on postcranial characters 
and found instead that anseriforms fell out within a huge, newly 
defined Ciconiiformes (now including Gruiformes, Charadriiformes, 
Phoenicopteriformes AND Anseriformes - even more extensive that the 
Ciconiiformes of Sibley and Ahlquist), and galliforms were the 
sister-group.

So there you go: there is general consensus, and a great deal of 
material evidence, that galliforms and anseriforms do form a clade, 
but there will continue to be dissention and argument about it. 

While on the subject of neornithine bird evolution, this just out..

BLONDEL, J. and MOURER-CHAUVIRE, C. 1998. Evolution and history of 
the western Palaearctic avifauna. _TREE_ 13: 488-492.

DARREN NAISH
darren.naish@port.ac.uk