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RE: Bipedal apatosaurs and stegosaurs?



Nick Longrich wrote (quoting Robert J Meyerson):

> > All this would use up a lot of energy.  It would be far more
> > efficient to stay on the ground and feed on what is readily
> > available, then move to the next tree (especially in a pine forest)
>
>       The real problem with this is that it is not anatomically
> possible. As has been pointed out, diplodocid necks at best stick
> straight out, the Dicraeosaurus illustration I looked at actually
> had it pointed *down* slightly. Diplodocids would make absurdly bad
> giraffe-style browsers because of the downard direction of the neck
> and short forelegs that only compound the problem. Either they
> grazed, or they reared.

Exactly.  Another point I'd like to make, that I tried to make in an
earlier post, is that it is absolutely not space efficient in a
semi-dense to dense forest to be a Diplodocoid walking around on all
fours.  Here's a crude diagram as seen from above: (It will only work
if you have an equal-area font though)

Diplodocus on all fours:         Brachiosaur:    Rearing Diplodocus:
       ******                     *******             ********
       *TREE*                     **TREE**             *TREE*
        ****                       ******               ****
  **     A               **          A                   A
 TREE    |              TREE         |                   |
  **     |               **         _|_       **         |     **
         |      **                /  |   \   TREE       _|_   TREE
         |     TREE               |      |    **       / | \   **
         |      **                |      |            |     |
         |                        |      |            |     |
         |                         \    /             \    /
*       _|_                          \ /                \ /
      /     \             **          |                  |
     |       |           TREE         |        **        |                   
     |       |            **          |       TREE       |
     |       |                        |        **        |
     |       |                                           |
      \     /        **                                  |
        \ /         TREE                                 |
         |           **   
         | et cetera on the tail... 

Whereas the "A" is the head of the sauropod and they are all about equal in 
size.  This shows that a rearing Diplodocoid would be much more compact than 
one on all fours, and thus much more manoeuverable in a forest than basically 
a 90' beam.  It would be nearly impossible for a Diplodocoid to move sideways 
in a forest if it was on all fours, so the only viable option in a forest was 
to them to have reared and walked bipedally.

Peter Buchholz
gpb6845@msu.oscs.montana.edu

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