Re: Coelurosaur Analysis update, with Graciliraptor, Atrociraptor, Sinusonasus,

[Tim Williams <twilliams_alpha@hotmail.com>]

Mickey Mortimer wrote:

> Note I used the definitions of Aves and Avialae sensu Chiappe (1996) and
> Gauthier (1986) (Aves = Archaeopteryx lithographica + Vultur gryphus;
> Avialae = Vultur gryphus <- Deinonychus antirrhopus).

I was confusing the respective definitions of Aves and Avialae.  Further, 
under your phylogeny, Aves and Avialae are not equivalent in content, with 
the former being much more inclusive than the latter.

> > > Maniraptorans are basally herbivorous in this phylogeny, with
> > > deinonychosaurs and birds both developing carnivorous clades
> > independently.

And the opisthopubic pelvis is primitive for Maniraptora.  A functional 
hypothesis consistent with this topology is that the pubic shaft swung back 
to allow for a more capacious gut, associated with herbivory (convergent on 
Ornithischia).

> Avialae requires a sensu too, as Avialae sensu Gauthier
> and de Queiroz (2001) is (feathered wings homologous with Vultur gryphus 
> and
> used for powered flight), which would be the Omnivoropterygidae + Aves node
> in my topology.  Assuming neoflightlessness for Caudipteryx, it could
> potentially be much more inclusive.  Hence the crappiness of 
> apomorphy-based
> clades.

Agreed.  Under your phylogeny, _Protarchaeopteryx_ and _Caudipteryx_ would 
be the basal taxa of the apomorphy-based clade Avipinna (Gauthier and de 
Queiroz's, 2001) .

The idea behind apomorphy-based clades is well-intentioned; but the 
definitions are often difficult to apply with accuracy.  The apomorphy-based 
definition of Avialae is especially contentious: "feathered wings homologous 
with _Vultur gryphus_ and used for powered flight".  First of all, the 
apomorphy in question ("feathered wings") is actually two characters roled 
into one: feathers bipinnate (=closed vane) and coplanar.  Second of all, 
the definition in question relies upon an inferred function or behavior 
("powered flight").  We'll never know for certain if _Archaeopteryx_ was a 
powered flier, or was merely capable of some less demanding form of aerial 
locomotion.



Tim

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