Re: Tyrannosaur numbers

[Phil Bigelow <bigelowp@juno.com>]

FWIW,
White et. al (1998) took depositional environments into account in their
paleo population study.  All depositional environments were sampled. 
Their stratigraphic control was also reasonably well-constrained.

Paleo population studies in terrestrial paleoenvironments are very
difficult to conduct for myriad reasons (some problems are theoretical
and some problems are practical).  The 4% number for _T.rex_ is about the
best approximation going at the moment.

<pb>
--

On Tue, 24 May 2005 04:39:19 -0700 (PDT) don ohmes <d_ohmes@yahoo.com>
writes:
> It seems to me that there may be a slight positive
> preservational bias re tyrannosaurs. The old water
> hole was a logical place for that final fall for
> several reasons, and a good place to get fossilized.
> 
> --- Phil Bigelow <bigelowp@juno.com> wrote:
> > 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
> > discoveries.
> > 
> > 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>
> > writes:
> > > 
> > > 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
> > > 
> > > 
> > > 
> > > 
> > 
> > 
> > 
> 
>