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Re: Upright bipedalism in dinos

Skip Dahlgren writes: 

>First, thanks to all who responded to my arachnid question.  The critter was 
>variously identified as an amblypygid, a "wind scorpion," a "sun spider," a 
>"whip scorpion" or "false scorpion," and a solpugid (or solifugid), with this 
>last being the odds-on favorite

As amblypygids and solifugids (really the only two choices; the other names
apply to one or the other) look very different from each other, a quick
check in a picture book on inverts ought to solve your puzzle.

>My question:  are there any known fossil dinos which may have had an erect 
>posture similar to that of the penguins?  The secondary question would be: 
>are there any other birds (ancient or modern, other than those leading to the 
>penguin line) which show similar adaptations (primarily erect posture, but 
>also horizontal/quadrupedal locomotion)?

You must understand that the upright stance of penguins is a consequence of
their hind limbs being reoriented to the posterior end of their bodies as an
adaptation for swimming.  You can see the same sort of thing to a lesser
degree in some other seabirds (notably the extnct Great Auk);  loons have
shifted their feet both backwards and sideways, so that they can barely
progress on land at all (as did the extinct hesperornithids).  I would
therefore not expect to see such an adaptation in a purely terrestrial animal.

Mind you, birds can alter their posture, so that they can at times have
their bodies quite vertically aligned (a robin on your lawn can do this);
and many open-country birds regularly sit quite upright.  A prize case is
the peculiar Plains-Wanderer from Australia, a superficially quail-like
shorebird relative that literally runs around on tiptoe in an extremely
upright posture.  However, these are behavioural posture changes, not the
sort of obligate postural shift you see in a penguin.

I don't think anyone has argued that although (say) Tyrannosaurus may have
normally held its body parallel to the ground, it could not rear upright if
it wanted to.
Ronald I. Orenstein                           Phone: (905) 820-7886 (home)
International Wildlife Coalition              Fax/Modem: (905) 569-0116 (home)
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