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Re: Coelurosaur Analysis Update featuring Buitreraptor (Practical)



Mickey Mortimer (mickey_mortimer111@msn.com) wrote:

<Why should it be?  It was only assigned to Allosauroidea (Lamanna, 2004) and 
Tetanurae (Calvo et al., 2004).>

  Should I play twenty questions? What puts *Megaraptor* next to *Calamosaurus*
et al. with *Tanycolagreus* instead of, say, with carnosaurs, possibly adjunct
with carcharodontosaurs, or even a dromaeosaurid as originally proposed? And
then, why not?

<I said it was most probably incorrect.>

  Given the number of "improbable" portions of this topology, the only part of
the tree I might even not question so far is the (carnosaur (tyrannosaur
(ornithomime + maniraptor))) generality and perhaps the bird topologies, but
that is due to a [I profess] unfamiliarity with the distinct morphologies of
these birds. Thus this entire tree is rife with improbabilities that outweighs
any of the "improbabilities" in the TWG analyses, Rauhut's topology in both
thesis and published, and Holtz's analyses.

<Nothronychus' position might be due to its very short tail, but it's never 
liked being a therizinosaur in my analysis.  Probably since I have so few
therizinosaur synapomorphies included yet.>

  Why are there no character supports listed? Probably? I would like to know
why.

<Sapeornis and Omnivoropteryx both have oviraptorosaur-like skulls, which is no
doubt affecting their placement.  I've said before I'd call Omnivoropteryx a
caudipterid if it didn't preserve postcrania.>

  The problems with viewing the skull through the interpretation of a matrix
imbedded x-ray image would make me suspect it useless to assess characters
from. CT-scanning would help, if this could be done. It is not apparently
possible, from the X-ray images, to determine what the shape of the
surangular/dentary articulation was like, the shape of the articular or
quadrate (if even present), the form of the postorbital bar (if present), or
even the presence or shape of an antorbital fenestra. As for why these skulls
are "caudipterid" ... based on what characters known only in caudipterids would
this be likely to be true? I do see the similarities, but is this based on
shortening of the snout? I see the same condition in shortening the facial
region of *Shenzhouraptor* to same effect. 

<Therizinosaurus has never claded with other therizinosaurs in my analysis. 
This was actually the closest it's come.>

  What features, then, are found to group the taxa together in typical
"segnosaurid" topology found? And why doesn't *Therizinosaurus* possess these?
Such as the autapomorphic caudomedial "spur" of the humerus, or the strongly
developed epicondylar crests, the anterior orientation of the distal articular
condyles without ventral extension, the supracondylar "ridges" within the
dinstal cranial fossa, and the narrowness of the intercondylar groove.

<Makovicky et al. argue the lack of a supraglenoid butress flange, proximally
placed manual ungual flexor tubercles, non-appressed radius and ulna, and lack
of a coracoid subglenoid shelf in Deinocheirus are unlike ornithomimosaurs.>

  But does this relate to the shared features of the manus and humerus that ARE
present? That is, 1) the reduced size and anterior position of the
deltopectoral crest, 2) the reduction of the internal (medial) tuberostity
(what I call the adductor crest), 3) the length of the humerus to it's proximal
or distal widths, 4) the reduction of the medial twist of the distal end, 5)
the loss of definition of distal crests and subcircular distal profile, 6) the
first metacarpal exceeding 75% of the second metacarpal's length (they are in
fact subequally long), 7) and the coincident nearlly even metacarpal-phalangeal
joints across all three manual digits, 8) the extreme length of digit 1 nearly
even with digit 2, not to mention shape of the proximal ulna, the distal
ulna/radial morphology, vestigialization of the carpals, etc. Changes of the
manual unguals, shape of the radial and ulnar shafts, bracing of the glenoid to
prevent lateral eversion of the humerus or alter the muscular insertion, and
even the presence of a developed distal fossa of the humerus, shortening of the
ventrocaudal coracoid process where the sternum contacts, and the slight distal
expansion of the scapulae with their greater elongation compared to other
ornithomimes can easily be size related features comparing to a more predatory
use of the forelimbs while retaining ancestral length. It could be a huge
oviraptorosaur, but I do not think this is likely given the bulk of the data.
It could be a lot of things, but parsimony seems to dictate it's arms are
ornithomimosaurian and the features Makovicky et al. note are absent may simply
be reversals from a derived position *Deinocheirus* holds near ornithomimids
proper (if that). BTW, Mickey, thanks for the characters supporting Makovicky
et al.'s claim.

<That was actually a typo for Scansoriopterygidae in my post.>

  Ahhh. Maybe we can actually get a less than monotypic scansoriopterygid
topology at some point with additional species at some point. These
"pseudo-pterosaur-dino-imps" that they are are odd enough, though.

<Not sure offhand.  It jumps around a lot in Maniraptora.>

  The absence of a lot of derived features doesn't help this taxon.

<The condition of its metatarsals would tell us very little, since basal 
ornithomimosaurs aren't arctometatarsalian.  The clade is not diagnosed by its
namesake.>
  
<I suppose my lack of phylogenetic taxonomy here could have been confusing, but
I thought I got the ideas across.  But if you insist... Technically,
Therizinosauria* can't exist in my tree, since Therizinosaurus is closer to
Oviraptor than to Segnosaurus et al.. Therizinosauroidea sensu Clark et al. and
Therizinosauridae sensu Zhang et al. and Clark et al. are equivalent to
Enigmosauria in my tree.>

  To what again? An unnamed and undefined clade? Currently, a definition of
Oviraptorosauria includes *Oviraptor* but not birds, making the therizinosaurs
oviraptorosaurs, instead.

<It's always closer to Troodon than IGM 100/44 is in the TWG matrix, and in 
Norell et al. (2000) as well.  Not so in this run of mine.>

  This is not surprising given the juvenile nature of GIN 100/44 as possibly
useless in a phylogenetic study. Note that including juveniles in a cladistic
matrix can skew the arrangement of taxa and place juveniles as taxa on their
own even when adults of the same taxon are included. That is, I think, a good
argument for the exclusion of GIN 100/44 from any cladistic analysis. As for
the IGM/GIN dichotomy, notice that "IGM" is the abbreviation for the Geological
Institute of Mexico (Instituto de Geológico de México), whereas GIN is the
Mongolian counterpart (Geological Institute, Mongolian Academy of Sciences), as
used by the Mongolians and, lately, the Polish studies. Using IGM is confusing,
and only the American-led or -incorporated studies use it, which seems to me a
weak reason to continue using it as correct nomenclature for specimens.

  Cheers,

Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


        
                
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