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RE: Brain cancer in Gorgosaurus



> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Kimba4evr@aol.com
>
>
> Lurking non-professional with many questions on this, can someone
> please explain in laymans terms?
>
> How can a tumor, which is soft tissue, be preserved in a fossil?

That is the $64k question here. While it is true some soft tissues can, in
pathological situations, be mineralized in life, and in rare situations be
mineralized post mortem, there is a BIG question as to whether the "tumor"
is really anything other than misplaced damage skull bones.  A histological
section could answer this.

> Can anyone be sure the functions of a dinosaurs brain regions
> coincide with the same function in modern animals?  ie: is the
> section of the brain that controls motor function in modern
> animals necessarily in the same place on a dinosaur to result in
> the tumor affecting the described areas?

Functions of the different parts of the brain are highly conserved in
vertebrates, so this isn't really a big problem.  Whether the "tumor" is a
tumor is a problem, though...

> The article claims the dinosaur had suffered a torn tendon in the
> left leg - again, a tendon is soft tissue which generally is not
> revealed on a fossil, how could they make this conclusion?

Tendons can, on occasion, ossify.  Additionally, damaged tendon insertion
points might indicate damaged tendons.

> The link provided to the article in Discover Magazine
> definitively states the dinosaur was a female.  The exerpts in
> Mary's post pertaining to evidence pointing toward it being a
> female I did not find in the link, it is my understanding that
> fossil evidence has yet to provide a clear definition between
> genders.  Is that understanding outdated?

No, you are correct, and the authors in question are speaking beyond the
evidence.  We still do not know how to "sex a rex", unfortunately.  There
are grave questions about the chevron-based evidence of determining
archosaurian sex.

But, sad to say, vertebrate paleo is a field where some people will often
claim definitive answers to what are actually only inferences or
speculations.

> Are fused vertebre in the tail section found in other fossil
> specimens to support this theory or in any modern animals?  Seems
> to me evolution would not have been so careless as to make one of
> its highest priorities, mating, an occurance to cause significant
> injury, except of course between rivals.

Well, a fair number of animals engage in sexual behaviors that produces
non-lethal damage: scratches, scrapes, bites, etc.  So long as they do not
seriously hinder the partner, evolution wouldn't necessarily select against
this.

(Note that some gastropods engage in sadomasochistic hermaphroditic sex:
more details if you wish on request...).

                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