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Tyrannosaurids, skippy, and sterna



Greetings,

To update folks: forget everything you've known about the sternum in
tyrannosaurids and Scipionyx.  In NEITHER case is the element(s) identified
really the sternum.  For the former, wait for the forthcoming T. rex
monstergraph by Brochu; for the latter, either updates by Dal  Sasso &
Signore, or the Basal Tetanurae chapter of Dinosauria II (whichever comes
first).

At present, the only definitely confirmed ossified sterna within Theropoda
are restricted to Maniraptora; all non-maniraptoran incidents are
problematic.

As for ossified uncinate processes: have not seen these in any tyrant yet.

As for uncinates and air sacs: given the strong evidence (from axial
pneumatic structures) for some air sac systems throughout Theropoda, one
doesn't need ossified uncinates to run an air sac system.  Tyrant skeletons
are HIGHLY pneumatic, from the skull through the vertebrae.

Witmer has several students working on cartilage structures in living and
extinct vertebrates; not surprising, a lot of functional anatomy exists in
this poorly-preservable form.

Hope this helps.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796