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Re: Feduccia (was: polarity of bipedality in dinosaurs)



At 07:01 PM 9/26/96 -0400, Dinogeorge wrote:

>I'm not as confused as you might think, my man.

        Yo, my man, that's dope!  I didn't know this list was goin hip hop!
        Werd!  Lemme break it down for you one time...

[no reply here, so I'm answering that...]
        Still, no one has answered my challenges about the
"Phytodinosauria".  I think I've seen this clade on just about every
Dinosauria cladogram or taxonomy to come from any member of this list.  Does
anyone want to speak up?

>I'm not presenting my own theory here, just an argument as it is presented by
>BADD cladists.

        Yet these become problems to be "resolved" by your BCF theory.

>According to them, since the cladograms say birds are dinosaur
>descendants, they must have evolved flight from the ground upward, because
>the earliest known dinosaurs were cursorial ground-dwellers.

        How many paleontologists believe this reasoning today?  Could we
have a hand vote?  Y'know, I never met a single element of cladist theory
which supports this conclusion.  Perhaps it is slightly more parsimonious,
but then, look at what parsimony did with the swim bladder and the tetrapod
limb.  I truly hope that you and the ornithologists are grossly exaggerating
the prevelance of this reasoning, or misrepresenting this side of the story.

>The cladists generally leave the details of just how this might have
>happened to others whose interests lie more in that direction. This
>strikes me as rather arrogant, but that's how some cladists are
>these days.

        Why?  Because they choose to specialise in what they know best,
systematics?  No matter how good a paleontologist I become, I hope there
will never come a day when there is not at least one issue in dinosaur
paleontology on which I will acquiesce to another scholar on.  The idea that
one worker can answer every question is arrogant, the attempt to concentrate
on only one aspect of a phylogeny is merely short-sited.

>The paleornithologists scoff at the idea of avian flight evolving from the
>ground upward (rightly, in my opinion)

        Funny, I certainly don't scoff at your BCF theory, no matter what I
say.  Why?  Because I think there is a germ of truth to it, and I recognize
the work that went into it, the intense thought and careful approach.  I see
no reason to scoff at hard work aimed at challenging our assumptions, even
if that work does not result in a theory which carries the day.

>which in turn leads them to scoff at the cladistics (wrongly, in my opinion).

        My lord!  You are defending cladists!  Or is it just their data?

>Dinosauria, so an increased theropod sacral count to, say, 4 or 5 may have
>had little to do with cursoriality or body support at first.

        Didn't this count increase independantly in the ornithiscians?  that
would seem to be at odds with your theorizing below...

>As Gatesy has pointed out, an increase in the sacral count could be
>related to the changes in the way the caudal and upper hind limb
>musculature worked, perhaps for balance during perching.

        Or perhaps for any one of a dozen other reasons.   Whatever they
were, they seem to have been common threads in dinosaur evolution, not just
in theropod evolution...

>In small dino-birds, the caudal musculature certainly became exapted
>for controlling the tail airfoil, and one can account for an
>increased sacral count and elongate ilium on this basis.

        If I recall correctly, iguanodonts have their tails locked in place
by tendons, yet they have quite a few sacral vertebrae.

>long ilium and increased sacral count of later theropods (ceratosaurs up)
>were well suited for further evolution and exaptation into a cursorial
>lifestyle, as you note:

        Or it could just as easily have made the reverse transition...
        Let's be serious here.  Although I'm not prepared to argue the point
about bird arms that John C. McLoughlin brought up, I will point out that
theories such as the one Tom Holtz presented concerning the addaption of the
tail as a dynamic balance reverse this neat little trend of yours so that
cursorial adaptions make flight easier.

>In later birds, the sacral count increased drastically with the shortening of
>the tail, even in small Mesozoic birds that weighed but a few ounces. Thus,
>considered by itself, a sacral-count increase is not necessarily an
>exclusively cursorial adaptation,

        Then why did all of your "cursorial dinobirds" retain their long
tails and long sacra, while flying animals *lost theirs*?

        Wagner
+-------------******ONCE AGAIN, NOTE NEW E-MAIL ADRESS******---------------+
| 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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