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swimming dinosaurs

In a personal question to me betty asked what i thought dinos did when 
swimming.  well of course the theropods must `trex water' or do the
head-up trex stroke (like headup breast stroke).  crawl was obviously
beyond their abilities given their arms, and no animal would naturally
use a back stroke or butterfly. 

seriously, here.  most animals have a density of near 1 (depending exactly
on their muscle to fat to bone ratios of course).  bone averages about
2.5 g/cm3, fat approx 0.65 g/cm3, and muscle about 1.2 g/cm3.  proteins
and organs tend to be about 1.0 g/cm3.  given that any animal can usually
float if it keeps its lungs moderately full of air and close to the
surface of the water.  so we should expect to see any dinosaur being able
to move in water for short distances.  how they propelled themselves is
a different problem.  for animals with a higher density, moving the limbs
would tense the muscles which causes the animal to sink.  animals with
low densities (lots of protein and fat), could likely swim reasonably well
without risking sinking.  of course, this all comes back to the endo/ecto
question too.  the more fat implies storage of bodily energy reserves.

i have two questions for the real experts on the list:
1.  do ectotherms have much in the way of fat reserves?  if so, what 
environmental conditions favour fat buildups in ectotherms?
2.  would sauropods be able to swim by keeping their tails and necks
near the water surface (and hence the lungs near the surface) with just
their heads marginally above water)?  or would they have too much 
mass below the water surface pulling them downward to be compensated by
inflated lungs near/at the surface?  if the adults could not swim thus,
would the juveniles have been able to do so?

i would really appreciate any references that people may have to help answer
these questions. 

Bonnie A.B. Blackwell,                          bonn@qcvaxa.acc.qc.edu
Dept of Geology,                                off: (718) 997-3332
Queens College, City University of New York,    fax: (718) 997-3299
Dept of Earth \& Environmental Sciences,        fax: (718) 997-3349
The Graduate Center, CUNY,                      fax: (718) 997-3513
Flushing, NY 11367-1597                         messages: (718) 997-3300