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Re: Greg Paul is right (again); or "Archie's not a birdy"



Matthew Martyniuk <martyniuk@gmail.com> wrote:

> To be fair, this again depends on how you define Aves. The oldest
> phylogenetic definition published for Aves is an apomorphy-based on
> anchored on the presence of feathers (Charig, 1985). In this usage
> (which is just as valid as any other pre-PhyloCode), feathers are not
> only a fundamental avian attribute, they are the *defining* attribute
> of Aves.


Well, if it's an apomorphy-based definition of Aves you're after, why
not go the whole hog and cite Linnaeus (1758):


"Aereae vocales Volucres pulcherrimae, Mandibulis protractis nudis,
Corpore pennis imbricato, Alis duabus pennatis volitantes bipedes
dignoscuntur.  Aves levissimae modicae magnitudinis, tectae pennis
plumisque, destitutae auriculis, labiis, cauda, scroto, dentibus,
utero, epiglottide, fornice, corpore calloso, diaphragmate."


So with this definition, we would define Aves based on the presence of
feathers; but we would have to exclude any forms with four wings
rather than only two (like _Microraptor_) and all forms that have
teeth or tails (by which I would infer Linnaeus perhaps meant a 'free'
tail, rather than a pygostyle).


No, I'm not seriously advocating that we adopt Linnaeus' 'definition'
of Aves.  I'm just highlighting that the concept of "fundamental avian
attributes" is as flawed as Linnaean typology.


> (How you define 'feather' is another story).


Characters are not cut from whole cloth, and feathers are no
exception.  Worse, because feathers are integumentary characters, they
are less likely to preserve in fossils.  Apomorphy-based definitions
are problematic generally, but feathers have their own specific
problems.





Cheers

Tim