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Re: A fundimental conundrum concerning gigantic theropods



At 06:11 PM 11/8/96 -0500, Rob wrote:

>IMHO, this is why being bipedal is an advantage; the animal gets its
>front limbs out of the way, and lets the hind limbs concentrate on
>speed.
        If this were such an advantage, why aren't Cheetahs bipedal?  Or, to
be fair, maybe dire wolves or lions?  Cats are extremely maneuverable in
most of their locomotory regimes, cursorial, jumping, maybe even arboreal.
I've seen one cat which was really impressive in a tree.  

        Something that people seem to not be paying much attention to is
that bipedality in archosaurs and quadrapedal cursorality in mammals are not
cut from the same cloth.  There were myriads of adaptive changes in both
groups which took place before _Pantera_ (oh, wait, is the Cheetah in that
genus?  I thought all the big cats except the Snow Leopard or something were
the same genus, but modern taxonomy is pretty conusing) and _Eoraptor_ came
along which may have fundamentally tipped the balance in the favor of one
stance or the other for whatever reason.  If _Pantera_ and _Eoraptor_ shared
a very recent common ancestor, and _Pantera_ and _Struthio_ shared a recent
common ancestor, then you could start to make comparisons.
        The comparison of forms that George and Rob are indulging in is
certainly not digging deep enough to have any hope of exposing why each
group chose the style it did.  Really, let's just take a quick breather from
sweeping generalizations based on modern analogues, and start looking at the
fossils.
        What do the fossils say?  You tell me.
        Wagner
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| Jonathan R. Wagner                    "You can clade if you want to,     |
| Department of Geosciences              You can leave your friends behind |
| Texas Tech University                  Because your friends don't clade  |
| Lubbock, TX 79409                               and if they don't clade, |
|       *** wagner@ttu.edu ***           Then they're no friends of mine." |
|           Web Page:  http://faraday.clas.virginia.edu/~jrw6f             |
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