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Re: World's 'largest dinosaur' found (with crocs & fish)



Peter Markmann (zone65@bigpond.com) wrote:

<I do wonder, then, why so many claim that most or all sauropods were 
dry-landers, if their remains are practically *always* associated with
water creatures ... I appreciate the catch-22 that water and the
sedimentary deposits it lays down are necessary for forming fossils. But
doesn't that mean that all fossilized dinosaurs lived in more-or-less wet
conditions? Or can fossilization sometimes be the result of infrequent but
heavy rainfall (such as in the Chinese desert finds)?>

  Well, let's get some stuff straight. First, marine environments accout
for the bulk of the world's fossil deposits. Other great, but less
abundant facies, include riverine or lacustrine (lake) deposits, mudholes
or asphalt deposits (all of which relate to the ability of water to entomb
and layer sediment ... these deposits are ALL sedimentary, forming nice,
clean, layers of rock around a fossil relatively quickly); other forms of
deposition include dune layers and ashbeds, and these are usually
cataclysmic, so tend to be rarer. Chinese desert finds are usually
lacustrine or riverine, in nature, and were formed during wetter periods.
Water and bones mix very well. Secondly, water as a nature of itself,
flows; if an animal dies anywhere near water, or is killed in a flood (as
an example), it will invariably be washed somewhere; this is the number
one explanation for the number of lanmd-dwelling animals found in water
environments for fossilization. To claim that this should show sauropods
as aquatic would then retroactively infer that nearly all terrestrial
fossils were aquatic. animals that die on mud flats don't usually go
anywhere or get fossilized, as current observances show: the bones simply
get eaten or decay. Third, the evidence that sauropods were terrestrial is
determined from the fossils themselves, not their environments; this
includes the culumnar structure of the legs, the orientation of the limbs
from their joints, and weight-bearing features aside from the legs
throughout the hips, shoulder, ribs, and vertebrae. The most reasonable
conclusion is that sauropods are accidentally preserved in water, not that
they were acquatic. 

=====
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.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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