> The crown group is far more robust and far more significant.
Significant, yes, but robust? I don't think its composition is
particularly stable (from the standpoint of fossils, of course --
from the standpoint of living taxa, anything between the crown and
its total clade is equally stable) and there are probably clades
diagnosable by a larger number of morphological apomorphies.
> Hence, if we'd need a phylogenetic definition of Aves RIGHT NOW,
> the only one that pertains to a clade that is proven beyond all
> reasonable doubt, and to a clade interesting enough to warrant such
> a familiar name, and that is not wrought with a whole damn lot of
> controversy, would be: "Anything closer to _Struthio camelus_ +
> _Vultur gryphus/Passer domesticus/Gallus gallus_ than to
> _Enantiornis leali_ + _Sapeornis chaoyangensis_ + _Confuciusornis
> sanctus_" or equivalent.
That's _Euornithes_. Do you really think this is the clade that most
deserves the name _Aves_? I mean, the known composition of the clade
in question is equivalent to something like (_Archaeorhynchus_ +
_Neornithes_). What is so important about it? What significant
apomorphies do we currently believe originated there?
BTW, using _Gallus gallus_ as a default representative of living
birds in phylogenetic definitions is a great idea. It is still
relatively deeply nested, we know its phylogenetic position with
great precision (unlike _V. gryphus_ and _P. domesticus_) and as a
model organism for evo-devo it is very well studied.