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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
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
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*?
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| Jonathan R. Wagner "You can clade if you want to, |
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