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RE: [Re: Sauropod Trunks]




> -----Original Message-----
> From: M.Alan Kazlev [SMTP:akazlev@kheper.auz.com]
> Sent: Monday, November 16, 1998 5:41 AM
> To:   archosaur@usa.net
> Cc:   dinosaur@usc.edu
> Subject:      Re: [Re: Sauropod Trunks]
> 
> archosaur@usa.net wrote: 
> 
> T
> Even if we allow the problem of short tails in brachiosaurs etc (& i
> _don't_ think this is such a serious problem - the tails were short only
> relative to diplodocid tails, they were still fairly long) still doesn't
> answer the problem of how blood could be pumped up so high against the
> force of gravity.  Hard enough for a giraffe - the pressure to pump blood
> to the head gives them such high blood pressure in the limbs they need a
> special hardening in their legs so their blood-vessels don't burst. 
> 
        ############################################

        Posture aside (which is very giraffe like in Brachiosaurs), the
ability to pump blood to any height
        is determined by cardiovascular constraints.  In modern reptiles,
the height is constrained to just a few 
        feet above the ground, even in very large specimens like salt water
crocodiles.  In fact, what IS the height of the tallest living reptile?  And
crocodiles have a 4 chambered heart.  High blood pressure is a relative
term, after all.  To me, this argues for sauropods being at least partially
endothermic.  And, Brachiosaurus has a shoulder height of 23-25 feet &
that's taller than the tallest recorded giraffe
        (19 feet).  So, the height is already so great that the animal isn't
viable unless it's cardiovascular system were designed to pump blood to a
great height.  Unless the neck is designed to be held horizontally, then
THAT posture (especially with a 20 foot long neck) would put tremendous
strain
        on the structure.  With the right sketal structure & ligaments,
tendons, & muscles; more erect could 
        require less effort to maintain.  Gravity is gravity: it pulls with
equal force on everything  of equal mass & an animal must by definition be
strong enough to move it's own bulk.  That's what gets older humans in
trouble who lose muscle mass (IF they do) as they age.  But, I still think
their is a clue in the obvious height above ground level limit on modern
terrestrial "ectotherms".  A 16 foot long, 
        1500 pound "salty" is what; perhaps 2 feet tall?  This "constraint"
is obviously far less rigorous on
        we terrestrial endotherms.  
        In any event, a mummified sauropod heart would be a useful find in
this discussion.  I'd like to hear the sauropod experts "weigh" in on this
one (sorry about pun). 

        Dwight