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Theropod Scapula questions

Message text written by INTERNET:mwhite@houston.rr.com
>1) Quadrupeds are generally reconstructed with the scapulae tucked neatly
parallel with the vertebral column.  However, bipeds, particularly
are usually reconstructed with the scapulae hanging down at a 45 degree

        Having really looked into the issue of scapulae recently (and found
a disappointing dearth in the published literature...), I feel compelled to

        The primitive reptilian condition is _not_ to have the scapula
parallel to the vertebral column, but perpendicular to it.  That is, the
long axis of the scapular blade is vertical, whereas the vertebral column
is horizontal (more or less).  Only two groups unambiguously reoriented the
scapula into a horizontal position parallel to the vertebral column:  birds
and pterosaurs.  (I say "unambiguously" because there's a possibility that
some of the gliding forms, like kuehneosaurs, may have had a more or less
horizontal scapulae, but the preservation of known specimens makes it hard
to ascertain that...)  Theropods (and other dinosaurs), as you note, have
an intermediate form, where the scapular blade is obliquely angled with
respect to the column; the precise angle is hard to determine (based on a
dearth of articulated specimens) and could well vary from taxon to taxon. 
Clearly, some theropods (e.g., _Unenlagia_) have a more horizontal blade
than primitive forms (e.g., _Coelophysis_).  I don't know for certain, but
I suspect the evolutionary trend towards reorientation of the blade has to
do with some changes in forelimb function:  the subscapularis and other
muscles that act as humeral adductors attachn on the blade.  Again, outside
of birds, this hasn't been examined much in the literature (and for birds,
Jenkins '93 is one of the few papers addressing it).

>2) How confident are we on the placement of the Theropod scapula along the

vertebral axis? A few years ago, someone on this list quoted Ken Carpenter
saying "As all naturally articulated dinosaur skeletons show, the first
rib bisects the scapula about midway along its length." Is this still the
case? <

        Quite confident, based on what few articulated specimens we have
(e.g., _Coelophysis_).  The scapular blades should be angled, and the
scapula-coracoid articulation is also angled, such that the coracoids
"cover" the front of the chest and almost meet.  Few mounted skeletons show
this, however, and have a wide gap between the right and left sides...

           ____/_\,)                    ..  _   
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           /\  '                        ^__/>/\____\--------
__________/__\_ ____________________________.//__.//_________

                     Jerry D. Harris
                 Fossil Preparation Lab
          New Mexico Museum of Natural History
                   1801 Mountain Rd NW
               Albuquerque  NM  87104-1375
                 Phone:  (505) 841-2809
                  Fax: ; (505) 841-2808