RE: Tyrannosaurus Rex: Evolution Of Change.

["Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>]

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Steve Smith
>
> I have been bothered by this for some time and I think it is a
> good discussion so here it goes. When I was a little kid growing
> up I always pictured T-Rex as a tail dragger who walked up right
> with his tail on the ground with this menacing look. He always
> looked bulky and threatening. I always loved looking at the
> painting of Charles Knight where T-Rex faced off against his old
> nemesis Triceratops. I always looked forward to watching "Land of
> the lost" or the "Valley of Gwangi" because it featured T-Rex. I
> even have the old Revell/Aurora kit of T-Rex which to this day
> remains my favorite and goes for close to $500.00 on ebay at
> times.

$500!!!!  Whoa!  (Not that I'm that desperate for cash or anything.)

> Then as time rolled on the view of T-Rex changed. He no
> longer was the bulky tail dragger, he became a lean swift killer
> who put the fear of god into any land creature. His image changed
> because of Scientists views and more so I believe because of
> Jurassic Park which I think are great movies.

Actually, the revisions in our interpretation of T. rex and other dinosaurs
had occurred long before JP came out: that was simply the time when these
revisions finally made it to hundreds of millions of people.

> But the question is
> is how do scientist really know what T-Rex looked like? How do
> they know if T-Rex wasn't a tail dragger or not?

In this case, the non-tail-dragginess of dinosaurs is found in their
footprints.  Even a modest reptile (like a monitor or an iguana) leaves a
tail drag mark as deep or deeper than its footprints.  In dinosaur tracks,
though, there is almost never a tail drag mark.

Incidentally, this and other observations (of the proportions in front of
and behind the hips) led people as early as the 1950s (for example, W.
Gregory's Evolution Emerging, in 1951) to restore T. rex and other dinosaurs
as non-tail draggers.

> How do we know what's the real T-Rex? Could Charles Knights
> painting be the correct version of T-Rex?

Almost certainly not.  Greg Paul (among others) has described specific
attributes of those restorations which do not match well against the known
skeleton.  This relates to one of the mantra's I taught my dinosaur class
this year:

Holtz's first rule of dinosaur restoration: the skeleton has to actually fit
inside the restoration.

> And could our new
> vision of this famous dinosaur be all wrong?

Certainly possible.  After all, nearly all the illustrations out there are
featherless...

> Awhile ago Jack
> Horner said that T-Rex was a pure scavenger and his arms were to
> tiny and weak to do anything but now evidence is coming forward
> to prove otherwise and Jack is even reversing his views in what
> he has said in the past.

He is??  (And, for the record, Horner's arguments have never been
particularly persuasive among theropod workers).

> Again who are we to say what T-Rex looked like in real life

Well, modesty prevents me... :-)

> unless we actually saw a living breathing T-Rex and if that
> happened I don't know if we would be around long enough to say!

Remember: all restorations of dinosaurs are hypotheses; they are subject to
revision wiht new data.

                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