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Re: Stokesosaurus (was RE: Megalosaurids & Dinosaur Genera List update #187)



Question: how "advanced" are the features that
differentiate a tyrannosaurid skull from other closely
related dinosaurs? Are these features basal,
indicating that the animal was (probably) close to
where tyrannosaurids branch off, or were they more
advanced, indicating that even more basal
tyrannosaurid material may lie in wait for discovery?

Brent

--- "Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>
wrote:
> > From: owner-dinosaur@usc.edu
> [mailto:owner-dinosaur@usc.edu]On Behalf Of
> > Williams, Tim
> >
> > > Stokesosaurus probably is (Holtz, 2001).
> >
> > Unfortunately, the assembled material for
> _Stokesosaurus_ - pelvic bones
> > (including the type), part of an upper jaw,
> braincase and tail bones - may
> > not belong to one taxon.  Although all the bones
> come from the Morrison
> > Formation, none of the material was found
> associated AFAIK.  The
> > ilium (sort
> > of) and braincase (definitely) look
> tyrannosaurid-like,
> 
> Actually, as Rauhut and I (different papers in
> press) have shown, even the
> ilium by itself (i.e., the type material) has
> derived features otherwise
> found only in tyrannosaurids and Eotyrannus.
> 
> Agree with the braincase.  Would be great if it
> were.
> 
> > Nevertheless, the braincase (basicranium; UUVP
> 2455) does document the
> > presence of tyrannosauroids in the Late Jurassic. 
> Whether or not
> > it belongs
> > to _Stokesosaurus_ is another question.
> 
> Agreed.  Furthermore, there are tyrannosauroid-type
> premaxillary teeth
> (described as "dromaeosaurid" teeth in Bakker's Gaia
> paper) from the
> Morrison.  My suspicion (no more than that) is that
> THOSE teeth belong to
> the ilium and/or braincase, and that the premaxilla
> referred to
> Stokesosaurus is another animal altogether.
> 
>               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
> 


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