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Re: Tarbosaurus?



I sent the following to George alone, mistakenly;
George, please reply to the list?

-----------------------------------------------------

Dinogeorge wrote:

<I claim that whatever sedimentological factors
operated in the Nemegt and the Hell Creek would sample
the two populations the same way. Show me how they 
would not. Show me how the speed or depth of the
water, the soil acidity, rainfall, size of particulate
matter deposited, etc. would affect the >ratio of
fossilized subadults to adults< in a tyrannosaurid
population. GET REAL, MAN!>

  I would reiterate Holtz' post, further, but feel an
additional point should be made. I have no opinion on
*Tarbosaurus* et al. regarding phylogeny. I think this
is my saving grace, no insult to the tyrannosaur fans,
like Tom. But, when it comes to the Nemegt or Hell
Creek, or Judith River, or Djadokhta, I have some
interest. Plainly, the sedimentological studies have
not been done in these places to fully understand the
taphonomic forces.

  Water speed has exactly the same effect on a young
tarbosaur as it would on you if you slipped and fell
into a Rocky Mountain or Great Plains river. Even a
small one could kill you, and in the same breath,
determine the fate of your bones 80 million years
hence. Depth would also factor in on how large an
animal the river could transport, likewise speed, and
how much silt the river moves for deposition. This is
intrinsic to taphonomy in wetter habitats. But no
comparative sedimentology has been done on the Nemegt
except from some of the original Russian works and
Eberth et al. on various correllative layers. This is
insufficient data to formulate paleoecological
theories that would in anyway influence further
hypotheses. One problem I have with some of Bakker's
seminal paleoecological work, fun as it all is to
read, is that the material and layers have not been
completely or thoroughly tested and studied. They are
now, to some degree, but I can see that the most
rigorous work being done now is in the Cedar Mountain
layers (Kirkland et al., others...) and somewhat in
Bissekty, Niger and Algeria, and Two Medicine layers.
This is due to current projects on the mein that
require understanding. (Fiorillo, Varricchio, Sereno
and others, Sues and others, Nessov and other, and
others.... :) ).

  This suggests, but does not constrain, the idea that
the Nemegt had best be mapped in all its braided and
not complexity before attempting an ecological
perspective or preservational consideration on the
matter.

  I'm not up on the chemical taphonomic processes, so
couldn't comment on that; particulate matter requires
mass and velocity stuidies in streambeds, and this
requires getting out and measuring ripple depth and
length, and bed width, and depth, and as far as I can
tell, there are no such beds available in the Nemegt.
Further, sediment particulate size maps have also not
been carried out. So this is an unknown.

=====
Jaime "James" A. Headden

  Dinosaurs are horrible, terrible creatures! Even the
  fluffy ones, the snuggle-up-at-night-with ones. You think
  they're fun and sweet, but watch out for that stray tail
  spike! Down, gaston, down, boy! No, not on top of Momma!

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