Re: Hell Creek environmental stresses: paper might offer insights

["Jaime A. Headden" <qilongia@yahoo.com>]

Stephan Pickering (stefanpickering2002@yahoo.com) wrote:

<Those who have followed, with intense interest, the MOR research on Hell
Creek environmental stresses, might be interested in the work of Linda
Buttel at Cornell, who uses computer visualizations so that one can
actually see population dynamics. Her latest paper:

Linda A. Buttel, Richard Durrett, S.A. Levin, 2002. Competition and
species packing in patchy environments. Theoretical Population Biology
61(3):265-276>

  I can see only one flaw in adapting this research to paleoenvironments:
the sample size of the Hell Creek is nowhere near as complete enough to be
able to adapt a program to such a formation.
http://palaeo.gly.bris.ac.uk/communication/Belton/evid.html proposes to
study the extinction dynamics by studying population densities (of all
species, not just dinosaurs) in an attempt to assess the exteinction rate,
by which the study itself suffers from the sample size. However, two
things are apparent:

  1) regionally within the Formation, such as between the Hell and Bug
Creek localities, populations are different. Add in the Sandy site, and
some Alberta exposures, and you will get several different population
extremes and compositions that will hinder such an assessment of mean
population density in any species. Some taxa are not found otherwise, and
would possibly be restricted generally.

  2) Horner and Benton both support the decline fo species before the K/T
boundary; if so, population sampling will be horribly affected by the
temporal variations in region and stratigraphy.

  Though I would like to see what a program would be able to do with such
a formation, such as was used to assess the relative structure of human
and mammoth populations to assess whether humans had anything to do with
the extinction of the latter, it is plagued by the incomplete sampling. In
well-sampled and diverse assemblages like the Morrison, we are still
finding new, large taxa (e.g., *Mymoorapelta*, *Edmarka*) which are very
distinct from their contemporaries, or absent from the sample (as in
*Myrmoorapelta*) otherwise.

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

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