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RE: crocodile reversed or normal



Ken Kinman wrote:

<And everyone agrees that Family Ornithosuchidae is a
member of clade Archosauria, but the confusion has
been in which archosaur subclade it belongs. In the
1980's it was placed in the subclade Ornithosuchia,
and there was no confusion. But in the 1990's, Sereno
discovered that it really belongs in Pseudosuchia.
Unfortunately Ornithosuchia was not cladistically
anchored on genus _Ornithosuchus_, so cladists have
the confusing situation of Family Ornithosuchidae
placed in Pseudosuchia instead of Ornithosuchia. This
used to confuse me, it seems to have confused you, and
it will continue to confuse others until the cladists
get their PT taxonomy straightened out...> 

  I don't want to sound prude, but this is just _that_
shy of being an _ad hominem_ statement. The confusion
is not on the phylotaxonomy, it's on the anatomy of
*Ornithosuchus*, which Gauthier and others had assumed
to clear pertain to a more avian than crocodylian
form. Hence the anchoring of Ornithosuchia on
something other than *Ornithosuchus*; its anatomy has
been considered pertinent and valid consideration for
that taxonomy for some ten years. Sereno (1991)
invalidated it, but he also turned a few other taxa
over, and revised Psuedosuchian and whatnot taxonomy,
which was cool. He's also done some interesting
changes in sauropod systematics, resulting in (along
with Coria and Salgado) some weird anchors that had to
be revised. This results in improperly understood
anatomy, not taxonomy. That taxonomy took it for
granted, and an extensive cladistic analysis like
Gauthier's and also Chatterjee's and Walker's
(previous considerations) shorter analyses did not
reveal what Sereno's did, does not justify dissing the
taxonomy in general. They are based on what are
considered robust and certain phylogenies.

  Properly, such taxa based on eponyms, like
Ornithosuchia, should include the type species as an
anchor. It didn't. Poo. That's one that's not, doesn't
mean its wrong. The original meaning (and inclusion)
of Psuedosuchia was to include crocodylian-like forms
(including aetosaurs) that did not related on the stem
to crocodiles. They do, so it includes crocodiles.
Poo.  Extensive comparative anatomy; and exactly which
and how many features do you find signify
relationship? Or not? A robust phylogeny with coinage
should require multiple tests of inclusion or
exlcusion of characters. Splitting (or even
identifying) character "bundles" or suites results in
more refined matrices. It more clearly allows included
taxa that have one or two of a three-character suite
to be compared. The "shortened snout" of
oviraptorosaurs is one example, when in fact more than
4 characters (form of nasals, palatals,
ectopterygoids, ratios of skull height/length,
width/length, form of pterygoids, ratio of
rostral/caudal palate halves, etc.) are involved.
Further finds would refine this, but these are all
diagnostic to some degree of oviraptorids. You _know_
there will be intermediate "long-skulled" and
"short-skulled" oviraptorids, and short-skulled
*Caenagnathasia* compared to long-skulled
*Chirostenotes* is an example of convergence, but not
having them does not mean they don't exist, and it
doesn't mean oviraptorids are therefore "more derived"
than caenagnathids. I actually see several
morphological steps between oviraptorids and
caenagnathids, and that the latter are quite basal,
but is this plesiomorphy?

  Is *Iberomesornis* more basal than enantiornithines,
or just a basal enant? Does it's morphology suggest
either, or does the supportive enant characters
converge in morphology, confusing the issue?

  This requires extensive testing and comparison, and
a lot of caution if a tree provides strange data. Or
anatomy suggests relationship. First see if its
convergent. Some of Sereno's 1999 taxa, including
Ornithomimoidea, and Perle et al.'s 1993 Metornithes
(Patterson, 1993) may be examples of jumping into the
"strange and unusual" as a presentation. Some features
"look" convergent, some are (or so I would assume),
tests, tests, tests. Don't diss the testers. Refine,
revise, require.

  I'll get to small dinos later.

=====
Jaime "James" A. Headden

  Dinosaurs are horrible, terrible creatures! Even the
  fluffy ones, the snuggle-up-at-night-with ones. You think
  they're fun and sweet, but watch out for that stray tail
  spike! Down, gaston, down, boy! No, not on top of Momma!

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