Re: transitional forms
geoffrey howells (ghowells@banda.ntu.edu.au)
Wed, 4 Sep 1996 15:09:16 +0930 (GMT)>
> Paul wrote:
>
> >I reviewed your post regarding the Devonian fish to amphibian
> >transitional sequence from August 28th. The data that you gave said the
> >following.
> >
> >578-552 mya no gills, lungs present, legs present
> >378 mya gills present, lungs present, lobe fins
> >368 mya no gills, lungs present, 7 digit hind legs
> >362 mya gills present, lungs present, 8 digit hind legs
> >
> >giving rise to amphibious Tetrapods... gills present, lungs present, 5
> >digits or less today
>
>
> Paul,
> I don't know where you got the 368 MYR "no gills, lungs present 7 digit hind
> leg." What I wrote was:
>
> >368 MYR-Ichthyostega-- much like Acanthostega but has 7 digits on his
> >hindlimb. He has lungs. His legs were only good for being in water. They
> >could not support his weight. (Coates and Clack, 1990, p. 67)
>
> Am I not correct that this is what I wrote and that you have not cited it
> correctly? Check the archive if you have doubt. I wrote of Acanthostega:
>
> >362 MYR- Acanthostega- has four legs, lungs but still has gills. (Coates and
>
> >Clack , 1991, p. 234) He has 8 digits on his front leg. His legs could not
> >support his weight either. (Coats and Clack, 1990, p. 66-67). He has fishlike
> >lower arm bones (Coates and Clack 1990, p. 67)
>
> Note that I clearly stated that Acanthostega had gills and lungs. The
> gill-less state was not found until 358 MYR ago. I do not know where you got
> the idea that there were no gills at 368 MYR but it was not from me. As I
> indicated here:
>
> >558-552 MYR A fossil found in Pennsylvania which is the second oldest
> >amphibian, has only lungs and no gills and is fully capable of walking on
> >land. (Washington Post, 117:(239): A2, Mnday Aug. 1, 1994)
>
> Have you read the original articles I cited? I would strongly suggest that
> you do so because you are missing several important pieces of information.
>
> Going through these point by point you wrote:
>
> >578-552 mya no gills, lungs present, legs present
>
> I never gave a 578-552 mya entry so you could not have gotten this from me. I
> gave a 558-552 Myr entry with these values. 558-552 should be at the end. You
> need to read things more carefully.
>
> >378 mya gills present, lungs present, lobe fins
>
> You left off the fact that during this time the panderichthids only had 4 fins
> (all other fish had dorsal and anal fins) These four fins were where the
> limbs are on tetrapods.
>
> >368 mya no gills, lungs present, 7 digit hind legs
>
> You didn't get this correct either. The 368 had gills. I said this was much
> like the acanthostega. They had gills also.
>
> >362 mya gills present, lungs present, 8 digit hind legs
>
> Unfortunately you got this wrong also. The 8 digits are on the forelimbs.
> This is why you should read the original literature rather than trying to do
> things by the seat of your pants. There are NO known complete hindlimbs for
> the Acanthostega! No one knows how many digits were there.
> M.I. Coates and and J. A. Clack write:
>
> "There are no complete hindlimbs so far known for Acanthostega but the femur,
> tibia and fibula are similar to those of Ichthyostega." "Polydactyly in the
> earliest known tetrapod limbs." Nature 347: p. 67
>
>
> Because of this, your conclusion:
> >
> >If your data is correct this shows oscillation rather than transition,
> >and is not as smooth as Stephen wisely noted. It can also be interpreted
> >as existing created diversity seen in sedimentary deposits at relative
> >points in time. It can be utilized by Steve Jones PC approach because of
> >the distinct and sudden appearance. A host of models can incorporate it,
> >but I believe that it is a poor proof of evolutionary transition.
>
> is based upon highly flawed data that was not at all what I wrote. My data
> was correct. Yours wasn't.
>
> glenn
>
> Foundation,Fall and Flood
> http://members.gnn.com/GRMorton/dmd.htm
>
>
Glenn,
I had assumed your 558-552 mya date was a typo. I thought you meant 358-352mya. Do you realize this is base Cambrian! I mean why did these things 'turn' intoamphibians? There wasnt anything much to live on on land? Anyway a 200myr gap
between forms isnt really a transition at all! The amphibian form had been known200 myr BEFORE the transition!!!