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RE: Megalosaurids



> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Nicholas Gardner
>
> Tom Holtz wrote:
> > > 5.What other species of amniotes were present?
> >
> >Other dinos in the quarry are _Iliosuchus incognitus_ and indeterminate
> >hypsilophodont-grade ornithopod.
>
> A tyrannosauroid?

Very likley NOT a tyrannosauroid; has essentially only a single feature in
common with the big guys (unlike _Stokesosaurus_), and that feature (the
prominent midblade vertical crest) is present in other, non-tyrannosauroid
taxa.  Not inconcievable it is a VERY basal tyrannosauroid, but no
compelling evidence for it.

> >
> > > 9.Should Torvosaurus and Poekilopleuron be sunk into Megalosauridae?
> >
> >See above.
>
> Whoops, I mean to ask if they should be sunk into Megalosaurus.
> >

Given, as stated, the question of the monophyly of all the material included
in _M. bucklandi_ beyond the dentary, this is a really problematic question.
Yes, some of the Stonesfield Slate material does share features with
_Torvosaurus_ and/or _Poekilopleuron_; if all the big Stonesfield Slate
material belongs to a single species, then there is a good case to be made
that _Torvo._, _Meg._, and _Poekilo._ form a monophyletic group.  Given that
"if",  one could argue the case to lump them all into _Megalosaurus_.

But, everyone, PLEASE remember that there are no "generic-ometers": if you
have a monophyletic grouping one can expand or contract your "genus" concept
as you see fit.  There isn't a "right" or "wrong" answer to this which is
independantly verifiable with new information.

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