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Re: Re: Pectoral Girdles



>>1)  As this is often referred to as "the first bird," did it possess the
>>standard bird-like pectoral girdle (fused clavicles+interclavicle=furculum,
>
>It possesses what has been interpreted as a furcula

The furcula is clearly there. Whether or not the furcula is homologous with
the fused clavicles+interclavicles is another story.
>
>>large coracoids articulating with the sternum (did it even have a sternum?),
>
>The specimens show no ossified sternum

 The newest specimen does show an ossified sternum, although nowhere near as
huge as those of ornithurine birds (nor should that have been expected).
>
>>blade-like scapula oriented parallel to the spinal column), or did that come
>>later?
>
>The shoulder joint is intermediate between some coelurosaur dinos and birds
>(Jenkins 1993). _Archaeopteryx_ did not have the full range of movement
>that modern birds have - for instance _Archaeopteryx_ could not raise its
>arms over its back as modern birds can.
>
>>2)  If the bird-like shoulder girdle came later, what, then, was the form of
>>Archaeopteryx's?
>
>See above. The question of "later" is tricky. _Archaeopteryx_ may not
>represent the direct line to modern birds, but an early offshoot. In that
>case the development of the shoulder girde in the direct lineage may have
>progressed beyond that shown in _Archaeopteryx_ by the Late Jurrassic, but
>we have no information on that.
>
>>3)  If Archaeopteryx DID have the bird-like girdle, what other dinosaurs do
>>we find this in?
>
>Some theropods do show advancements similar to that in _Archaeopteryx_,
>e.g. _Deinonychus_.

And Velociraptor, and a nice furcula and sternum in Oviraptor.
>
>Chris
>
>Jenkins, F.A. (1993) The evolution of the avian shoulder joint. American
>Journal of Science, 293A: 253-267.
>


Thomas R. Holtz, Jr.
Vertebrate Paleontologist
Dept. of Geology
University of Maryland
College Park, MD  20742
Email:Thomas_R_HOLTZ@umail.umd.edu (th81)
Fax: 301-314-9661
Phone:301-405-4084