You needed to get out of the house. You have been spending too much time on
the internet. :-)
>
>You'll recall I asked you if this article had a sketch of the anatomy of the
>thing, which is the all important question. You did not answer me, of course,
>and now I know why. There isn't one!This was a 3 paragraph blurb in the front
>of the magazine, that is entirely unhelpful on this issue.
>
What do you expect from Scientific American. It is a generalist journal not a
specialist. But while you were at the library you could have taken the
species name and gone to the ichthyology section and started looking.
>We have to go back and recall how this all started. Gordon R. Taylor wrote in
>his book:
>
><The real obstacles to such a move were the massive structural changes needed
>to make life on land worthwhile.To bein with,the fish would need legs simply
>in order to relieve the pressure of its body on the ground, which would
>compress the lungs. >>
>
>And Glenn responded:
>
><<Sorry to interrupt Mr. Taylor, but you know? Snakes seem to get along just
>fine breathing without legs. I can lay on my couch or the floor and breathe
>just fine. I think this guy is wrong. >>
>
>Well, it turns out a little research shows that Glenn is wrong. In a section
>that Taylor himself could have written, Michael J. Benton talks about the
>problems with the fish transition to land:
>
>"The major problems with life on land relate to weight and structural support
>as much as to the physiology of breathing air. A fish is buoyed up by the
>water and its body weight may be effectively zero. On land, however, the body
>as to be held up by some form of limbs, and the skeleton as all the internal
>organs have to become structurally modified in order to cope with the new
>downward pull of gravity. The backbone of a fish is adapted for the stresses
>of lateral stretching and bending during swimming, but the main forces to
>which a tetrapod is subject are caused by gravity. The vertebrae and the
>muscles around the backbone have to become modified to prevent the body from
>sagging between the limbs. The mode of locomotion of a tetrapod on land is
>generally different from that of a fish in water." [Benton, Vertebrate
>Palaeontology, Chapman & Hall 1990, pp. 46-47]
>
>Unaware of this text, Glenn brought up the "walking" catfish (the quotation
>marks around "walking" were put there by the writers of Scientific
> American, not I). I asked Glenn for some more information. Didn't get it.
>
Do I understand you to be saying that If I had understood this text, the
walking catfish would not be able to spend 12 hours strolling along Florida
roads taking in the scenery?
>What I did get was an accusation that I had denied their existence (an
>accusation Glenn now has to admit was baseless).
I certainly don't remember that. But since you are now the keeper of my
memory I can't seem to recall. :-)
> What I actually said was this
>example tells us nothing useful: nothing about its anatomy, but more
>important, nothing about its origin. Glenn, of course, assumes it is the
>product of evolution. He even assumes it is a transitional form, calling it
> a "modern example of fish in transition." It is upon such assumptions that
>evolutionary quackery is based. Always assume, never explain.
Everything is a transitional form from what its ancestors were to what its
descendants will be.
>
>Anyway, in response to my asking for more information, Glenn starts screaming
(Only because I am hard of hearing)
>"Why can't you admit you're wrong?" Like a latter day Torquemada, Glenn is
>more concerned with a coerced confession than with reasoned argument. Well,
>this sort of evolutionary fascism may work in Texas, but don't expect your
>thumbscrew method of debate to move many in the high culture of L.A.
>
Me and Torquemada are good buddies. We have a beer every Friday afternoon. I
will talk to him about you tomorrow.
>So I go to look up the article on the catfish. Nothing helpful. But I do
>redeem the time by finding the Benton section.Benton goes on to describe the
>various problems (echoing Taylor almost exactly) that had to be overcome.
>Among them:
>
> * New bones
In the paleontological case from the Panderichthys, there are new bones.
> * Defined elbows and wrists
this also.
> * Humerus and shoulder joints
Yep. In the fish, the bone that evolved into the humerus is quite different.
In the Scat Craig fossils, this bone in indeed intermediate.
Scat Craig material
"But although the tibia clearly belongs to a leg, the humerus
differs enough from the early tetrapod pattern to make it
uncertain whether the appendage carried digits or a fin. At
first sight the combination of two such extremities in one animal
seems highly unlikely on functional grounds. If, however,
tetrapod limbs evolved for aquatic rather than terrestrial
locomotion, as recently suggested, such a morphology might be
perfectly workable. Note that the forelimb of Acanthostega is
more fish-like than the hindlimb and could probably not be
brought into a weight-bearing position."~P. E. Ahlberg, "Tetrapod
or Near-tetrapod fossils from the Upper Devonian of Scotland,"
Nature, 354, Nov. 28, 1991, p. 301
> * Protective pectoral girdle ("This is because of the additional
>forces imposed by the role of the hindlimb in walking and support. The weight
>of the body would simply force the pelvic girdle of a fish upwards into its
>body cavity if it moved on to the land, and the girdle would twist about
>during walking." [p. 49])
>
> "In addition to the problems of locomotion on land, the earliest
>tetrapods had to modify the structures associated with feeding and
>respiration." [p. 49], viz:
>
As to respiration, I have already pointed out that the original transitional
amphibians did this by having BOTH lungs AND gills. Are you not listening?
> * Lungs instead of gills ("Living lungfishes have functional lungs,
> of course, and the same is ASSUMED for osteolepiforms and indeed most other
> early bony fishes" [pg. 50, emphasis added])
Not assumed, FOUND.
>
> * Semi-permeable skin coverings to cut down on water loss.
Skin is not preserved.
>
> And the BIG question is WHY? Why move onto land? The "classical"
>theory (e.g., Romer, 1966), is that depleted water sources due to drought
>forced changes in order to keep living in water ("Terrestrial locomotion
>evolved as a means of staying in the water!" [pg. 50]), but this has been
>criticized as lacking evidence. The "simplest" hypothesis, according to
>Benton, is that there were new food sources on land. No evidence for this,
>either. But the problems identified by Benton (and Taylor) remain.
>
Recent theories say that the move to land may be no more complex than that
food was available in the form of insects and worms. These forms were on land
earlier than the transition.
[snip]
> Also of interest is Kardong's admission at p. 334: "The musculature
>associated with the fins of early crossopterygians (rhipidistians
>specifically) was probably too weak to have supplied propulsive thrust
>directly for transport on land or to have borne the weight of the body out of
>water." He thinks the answer might be that their fins operated like "pegs"
>allowing a "pivoting" out of water. This does not solve the pressure problem,
>of course, which Taylor and Benton outline. On the next page, Kardong adds,
>"Because no one was there to record events, we cannot be sure of theselective
>pressures that favored the transition to land."
Jim, this is no admission. I have said this many times. The earliest leg
could not have supported the weight. See what I quoted above about
acanthostega and I have cited this before also. It was a transitional leg
i.e., a half evolved leg!!!! You are finally understanding something.
[snipped a great rambling which would win any case brought before a court of
law by confusing the heck out of everybody.] If I am ever in trouble I want
you to defend me.
>Sorry, this isn't Tegwar.
>
>Brian wrote:
>
><<Glenn, you ignorant dork brained dufus headed dweeb nosed slob!!!
>Quit begging already.>>
>
>This is unfair. You nose is not "dweebed."
Brian is near-sighted. Thanks for correcting that. :-)
glenn
Foundation,Fall and Flood
http://members.gnn.com/GRMorton/dmd.htm