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Tripodal Sauropods (was RE: Bipedal apatosaurs and stegosaurs?)

Rob Meyerson wrote:

> Diplodicids specifically.  The smaller species might be able to get away
>  with a rearing-for-feeding stance, where the loss of efficiency will be
>  made up for in the quality of the food source.

Why do you assume that there would be a great deal of energy lost by 
reaering?  It's basically a moderate pull with the back muscles and then 
simply having the whole body fall on the tail.  Probably not much more energy 
would be expended (proportionally) by you if you did 20 situps.  There would 
obviously be more energy expended by Sauropods less well adapted for this 
(like Brachiosaurs or Camarasaurs), but still the energy requirements would 
be minimal, unless of course you're advocating that they would rear, eat for 
a minute, go back on all fours, rear, eat for a couple of minutes, go back on 
all fours and so on, which is kind of silly.

> Even among the diplodicids, I have a hard time seeing a herd of the big ones
>  all rearing up to feed on the tops of the pines.  The loss of efficiency
>  aside, this kind of posture would make these animals more susceptable (sp?)
>  to predation.  Imagine a Diplodicus reared up, with it's head in the
>  stratosphere.  Along comes a hungry Allosaurus.  Even if the Diplo saw the
>  theropod coming, it would take a lot of precious time for the animal to get
>  all feet on the ground and to engage it's tail for combat.  During that
>  time, the allosaur could easily make an attack and cripple the animal long
>  before the Diplo would be in a position to do anything about it.  A
>  recipe for extinction, IMHO.

You seem to forget that on average most Diplodocoids (Diplodicids + 
Dicraeosaurids) were five to fifteen times the mass of their largest prdators 
and that they carried hefty thumb claws that could easily have impaled an 
attacking Allosaur.  If I was an Allosaur, I would be more scared of 
attacking a tripodal diplodicoid for fear of having it fall (on purpose) on 
me, than attacking a quadrupedal one and have it whip me with its tail.

Peter Buchholz

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