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Re: Tyrannosaur numbers

John Horner has an informed opinion on the number of _T. rexs_ that
existed at any one time, and from my limited experience as an interested
amateur, I think I'll agree with him.  _T. rex_ appears to be quite
common in the Hell Creek Formation.

For a number of years, paleontologists believed that _T. rex_ was a rare,
or at least was an uncommon, taxon.  But the reason for that belief is
simple.  After Barnum Brown and Harley Garbani retired, people just
stopped searching for _T. rex_ skeletons.  Things started to change
around 1988 after Kathy Wankel stumbled upon MOR-555.  Since then,
Horner's team has dug up a number of partial skeletons in Montana, and
Stan Sacrison and the Larson Bros. have done the same in South Dakota. 
Another _T. rex_ skeleton was found in Sask. Canada.   And in Alberta,
Canada, Phil Curie has dug up a few new skeletons and reopened old _T.
rex_ quarries.  Then there is the beautifully preserved South Dakotan
"Z-rex" and a number of other amateur finds.  All are post-Wankel

FWIW, shed _T.rex_ teeth (representing a variety of growth stages) are
common fossil finds.  In some facies (rock layers),  juvie(?) _T. rex_
teeth are the dominant theropod taxon.

As far as predator/prey ratios go, this only means that there must have
been *way more* prey species wandering around the late Maastrictian North
American landscape than we now believe.

If you have access to the scientific literature, get a photocopy of the
following paper:

White, P.D., D.E. Fastovsky, and P.M. Sheehan. 1998. Taphonomy and
suggested structure of the dinosaurian assemblage of the Hell Creek
Formation (Maastrichtian), eastern Montana and western North Dakota.
_Palaios_, volume 13:41-51.

White et. al estimate that _T. rex_ constituted 4% of the entire Hell
Creek dino population.  That is a significant percentage, and it is equal
to the Hell Creek dromaeosaurid, troodontid and pachycephalosaurid
population percentages, *combined*.

<pb> (who's been posting WAY to much recently.  It must be the increased
light levels of the season.)

On Tue, 24 May 2005 10:54:39 +1000 Benjamin Hughes <grombek1@hotmail.com>
> Hi all
> I'm relatively new to the DML, certainly no expert like manyof you 
> here, but 
> jut thought I'd add my bit. I have ideas and if I'm wrong then I'm 
> happy to 
> hear why.
> I have heard (coan't remember source, sorry) that there are very few 
> Tyrannosaur fossils ever found. Whether this means that few have 
> been found 
> out of a large amount still undiscovered, that few of the animals 
> ever 
> happened to be fossilised in the first place, or that there were few 
> Tyrannosaurs ever in existance at all, I am not sure.
> My point is that if it were true that there were few Tyrannosaurs, 
> then this 
> would most likely mean that it was simply because they were 
> innefective 
> predators, too big and cumbersome to catch faster prey, or to 
> compete with 
> slightly smaller predators.
> Is there any way of knowing without the actual fossils the number of 
> Tyrannosaurs that existed?
> ~Ben
> -~
> The Australian Discworld Convention - www.ausdwcon.org