Re: Segnosaurs ejected from AVES

["Mickey_Mortimer11" <Mickey_Mortimer11@email.msn.com>]

Ken Kinman wrote-

>       I would be interested to know how Beipiaosaurus would be coded with
> your six semilunate characteristics.  It's possible that segnosaurs (sans
> Beipiaosaurus) split off first, and that Beipiaosaurus then split off
> between them and the rest of the "true" semilunate forms.  In other words,
> Segnosauriformes sensu lato could be paraphyletic, and perhaps
Beipaiosaurus
> represents the transition to the "true semilunate".

Beipiaosaurus seems to have the same type of carpus Alxasaurus does-
semilunate shape, unfused distal carpals I and II, covers most of metacarpal
II and probably most of metacarpal I, proximal trochlea present.  The main
difference is that distal carpal II is larger than distal carpal I in
Beipiaosaurus.  So no, paraphyletic Segnosauria isn't supported by carpal
data.

>       I would also be interested to know if Beipiaosaurus had a convex
> coracoid glenoid, as that transition seems to be occurring around the same
> time.

It looks to be concave, as in other segnosaurs.  Hard to be certain due to
picture quality, but that's what I see.

> Segnosaurs clearly do NOT have a "true" semilunate, they do not meet
> the apomorphy-based definition, and I hereby remove them from my proposed
> Class AVES sensu lato.  I never thought they were a sister group to
> Caenagnathiformes anyway, and this clinches it for me.  Eggshell data and
> other morphological data will also help to distinguish segnosaurs from
Aves.

Ahhhhh!  Horrible decision!  (but a wonderful way to show how faulty
apomorphy-based definitions are).  So segnosaurs are excluded from the
Oviraptorosauria + Paraves clade simply because they have unfused distal
carpals?  You know that other more basal coelurosaurs (Sinosauropteryx,
ornithomimosaurs, Scipionyx, I think Coelurus and tyrannosaurs),
Acrocanthosaurus, most Allosaurus specimens and some Syntarsus specimens
have fused distal carpals too.  It's obviously secondarily developed in
segnosaurs.  Even if there wasn't such evidence, you'd still be commiting an
Olshevskyism (sorry George :-)  ) by valuing the fused semilunate over the
many characters suggesting Enigmosauria is monophyletic.  Actually, looking
at enigmosaurian characters in respect to my new recoding is giving me
doubts as to just how many valid enigmosaurian characters there are....

interesting.....

Mickey Mortimer