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Re: New AVES definition refined (more testable?)



Ken Kinman wrote-

> I fully expected my proposal to be controversial (but I was
> a little surprised just how strongly it is being dismissed before it is
even
> tested).  Mickey Mortimer's upcoming analysis will be an important first
> test, and *if* he can convince me that "enigmosauria" is holophyletic, I
> will certainly modify my proposal accordingly.

Might I ask you why I'm for some reason the lone individual whose
phylogenetic analyses you will trust?  I mean, sure I feel my analysis will
be _more_ accurate than others' published analyses (if only because I can
include more taxa, and everyone else's characters), but that doesn't mean
the others are inaccurate.  And various unpublished analyses probably have
the edge over mine, for the same reasons.  Mainly, I'm curious to see where
controversial taxa like Avimimus, alvarezsaurids, basal coelurosaurs, the
eumaniraptoran complex and basal birds end up.  The (Tyranno (Ornithom
((Segno, Ovirap) (Troodon, Deinonych, Aves)))) topology is virtually a given
these days, with all well done analyses coming up with it.  Why not trust
Holtz's, the AMNH team's or Longrich's analyses?  They all come up with
Enigmosauria too.  Doesn't that mean anything?

>      PRIMARY DEFINITION of Class Aves sensu lato (proposed):   Theropods
> possessing both a "convex coracoid glenoid" AND at least one the two
> following carpal characteristics:  (1) Distal carpals I and II enlarged
and
> fused into a single element with a distinctive semilunate shape; and/or
(2)
> this fused structure fully caps metacarpals I and II.
>     Notes:  Protarchaeopterx and Caudipteryx meet this definition even
> though they apparently lack the distinctive semilunate "shape".
Deinonychus
> also meets the definition, even though one of its metacarpals is not
"fully"
> capped.  Segnosaurians do NOT meet this definition, although Beipaiosaurus
> seems to approach it the best.  The segnosaurians are most likely the
sister
> group of Class Aves sensu lato, and therefore many of the supportive
> characters which are listed below will be found in some or all
segnosaurians
> (as noted).  Tyrannosaurs appear to be further out (contra Sereno's
> "Tyrannoraptora").

"And at least one of these two characters"?!  That sort of definition will
never hold.  We're after shared derived characters, not characters that have
a greater probability of being present.  You know Protarchaeopteryx doesn't
have a semilunate shape, nor do its carpals fully cap metacarpals I and II
(extends less than halfway across mcI).  Oops.  Not an avian I guess.....
But that's okay.  If you can justify throwing out segnosaurs, surely the
fragmentary Protarchaeopteryx won't be a problem to find excuses for....
Actually, I wouldn't be surprised if oviraptorids and paravians perfected
the semilunate in parallel, but we have segnosaurs that also have a true, if
unfused semilunate.  Finding out where among enigmosaurs Protarchaeopteryx
goes should clear the distribution up to decide which is more parsimonious.

And your characters are either-
A. Those supporting segnosaurs as more basal than oviraptorosaurs and
paravians, but which are far outnumbered by the enigmosaur characters (5, 7,
8, 14).
B. Those which are unknown in segnosaurs, so are ambiguous synapomorphies of
your "Aves" (1, 3, 4, 10)
C. Those that are present in segnosaurs (6, 9, 11, 12, 15, 16)
D. Those with other problems-
2 is an obvious reversal in segnosaurs, and ambiguous as an
oviraptorosaurian-paravian synapomorphy anyway.
13. "The fused distal carpal element has often fused to the metacarpals".
Often, as in three to four times (three in small clades- Avimimus,
alvarezsaurids, confuciusornithids).  Mammals can be characterized by often
being bipedal by the same logic.
And a couple further comments-

>      (4) Laterosphenoid head small, and snovial joint small or absent
> (unknown if this also occurs in segnosaurians or not).

Oh good.  Perhaps you could tell me what this character means then?  I've
been curious for a while now.

>      (6) Preacetabular blade of ilium dorsoventrally elongated (also in
> segnosaurians, but it is distinctively expanded laterally).

But that lateral expansion is an apomorphy of segnosaurs, so it won't
exclude them from exhibiting the character.  It's like saying "neornithines
have toothless beaks (also in Falconformes, but theirs is raptorial and
decurved)".

>      So there you have my viewpoint as it stands at present.  If Mickey's
> analysis convinces me that "enigmosauria" is holophyletic, I will modify
my
> proposal accordingly.  However, I think even he may be surprised, and that
> the case for "enigmosaur" paraphyly is a very viable alternative.
According
> to this alternative view, "enigmosauria" is based on plesiomorphies and
> parallelisms.  We shall see.  As always, *constructive* comments are
> welcome.

So, in short, you haven't found anymore evidence since last time
(http://www.cmnh.org/fun/dinosaur-archive/2002Feb/msg00094.html) and have
chosen the non-parsimonious option 2-
"2. Decide that segnosaurs are more basal than oviraptorosaurs against the
current evidence, in which case I'll have nothing more to say on the topic
until my new analysis comes out.  You'd just be using subjectivity in which
characters you "found important", not science, so there would be no logical
way to convince you otherwise."

Mickey Mortimer