Re: E and P of pterosaurs - more comments

[Unwin <h0662eka@rz.hu-berlin.de>]

Here are some short responses to Peters comments on my earlier mailing. 


>First of all, let me mention one compliment I forgot to pass on earlier
>regarding David's observations. He was exactly right in anticipating
>that Preondactylus would have a higher premaxilla ascending process than
>previous reconstructions showed -- more like Dimorphodon. A
>reconstruction justifies David's foresight.

I would be gratified if any actual new evidence was cited to support my 
reinterpretation. It isn't, so I'm not. 


>I have to wonder, though, about David's comment above. What will strike
>the reader upon even a casual glance at his 2003 figures is that they
>all appear to be copies of extant figures, rather than new drawings --
>starting from scratch. The same holds true of many of David's papers,
>excluding his 1988 report on Dimorphodon, which had no precedent. I have
>no doubt that David has actually seen the fossils. A carefull tracing of
>some or many of the fossils will reveal flaws in their precedents. A
>tracing of the figures themselves will not.

So, the plan is that I travel around the world with my sketch pad and 
pencil, redrawing each of the 50 or so line drawings that appear in my E 
and P of Pterosaurs paper on the basis of the original specimens. Would 
someone like to step forward with the cash to do this, oh and at the same 
time you can try convincing my boss to give me a few months of work for 
the travelling. And don't mention that at the scale they are drawn, my 
sketches will look almost exactly like the published versions.

Fortunately, the validity and reliability of cladograms (including my 
own) do not depend in any way whatsoever on my drawing skills. 


>David's matrix has a higher proportion of filled boxes than any
>preceding it, and this is one reason given for using suprageneric OTUs.
>If that's the goal, then great. I still think it breeds chimaerae.

So prove it. 


>I think the pterosaur interrelations problem is more difficult than
>anyone imagined two years ago when David's paper was probably due to the
>publisher, but thankfully and fortunately, it appears that there now is
>a critical mass of taxa to tell the tale -- if they are all employed. I
>applaud David's efforts to divide the spectrum of pterosaur
>interrelationships further, but I am disheartened to hear that the
>cladogram will be the same as before. 

This doesn't make any sense at all. Peters argued that analyses should be 
done at finer taxonomic scales in an earlier post, but is unhappy with 
the result when someone does just that. 


>Mine was similar, about a year
>ago, when it had a single clade "Pterodactyloidea" as all published
>cladograms do now. Here's what happened: the morphological gap between
>the highest rhamphs and the lowest pterodacs bothered me enough to dig
>deeper, and I hope David and others do the same. Evolution works in tiny
>steps and if you look hard enough you'll see the tiny steps, as I have.

Cladograms as I expect readers of this list are now well aware, are not 
intended to, and indeed do not, show evolution. Peters statement above 
exposes some extremely muddled thinking.   


>I would urge future geneologists to consider a number of Dorygnathus and
>Scaphognathus specimens as terminal taxa and not to consider Dory or
>Scapho a single taxon each. Here is where the former 'Pterodactyloidea'
>splits into four clades. Pay special attention to the manus and pedes of
>each. Some reassembly will be required. In all four cases, a size
>crunch follows that ultimately leads to the larger taxa we know and
>love. So, here's where the wee ones make their entrance before giving
>rise to the big ones. The Teyler's Museum in the Netherlands cares for
>some of these key taxa.

So this is based on intensive anatomical studies, accompanied by detailed 
drawings of each of the actual fossil specimens concerned right?   

I'll finish with another contentious proposal, which one might call 
Hennig's Law: 

'The quality, reliability and robustness of a cladogram is directly 
related to the amount of time and effort spent studying the specimens on 
which it is based.' 

I believe many of the citations given above are entirely consistent with 
this law.

Cheers,

Dave  

      




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David M. Unwin PhD

Institut fur Palaontologie, MUSEUM FUR NATURKUNDE 
Zentralinstitut der Humboldt-Universitat zu Berlin
Invalidenstrasse 43, D-10115 Berlin, GERMANY

Email: david.unwin@rz.hu-berlin.de

Telephone numbers:
0049 30 2093 8577 (office)
0049 30 2093 8862 (department secretary)
0049 30 2093 8868 (fax)
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