re: pteros, prolacerts, and Peters

[david peters <davidrpeters@earthlink.net>]

David Unwin wrote:

First, merely because a single analysis produced cladograms in which 
pterosaurs were paired with one or more prolacertiforms does not, in my 
opinion, mean that we should immediately accept this as the gospel truth 
and abandon any attempt to critically test this idea, or explore other 
possibilities. 


DP: Yes, keep testing! But in the meantime, don't install zeroes in matrix 
boxes that should have ones. David, did you disagree with any or all of my 
coding suggestions? Let's talk about them then! We can figure this out 
together!!   :  )


DU: Second, two of my colleagues have done exactly that which Peters has 
frequently exhorted us to do - carried out a detailed study of his 
'pterosaurs are prolacertiforms' analysis. The results of this work 
should be published later this year and, as I have mentioned before - 
with full permission from the authors - although they used the same data 
as that presented by Peters they do not support Peters findings. 


DP: It might be wise to have me review their work. I'd be happy to. Full 
confidence guaranteed. As always. Three working days max. 
      And please remember, it's not us against them, or them against me, we're 
all after the same truth. 


DU: This 
does NOT mean that pterosaurs were definitely not related to 
prolacertiforms - all it means is that, when thoroughly investigated, the 
data presented by Peters does not support this idea. 

DP: Then I suppose, when thoroughly investigated, the data [my data] supports 
another pterosaur outgroup, other than the Prolacertiforms? Or am I misreading 
this? You seem to be on both sides of this fence. Or should I read this that 
the data is inconclusive? If so...

Historically only a few characters have linked pterosaurs with archosaurs or 
dinosauromorphs: 1) The antorbital fenestra. 2) The simple hinge tarsus. 3) The 
tibia longer than the femur. 4) The shortened torso. 5) The anterior elongation 
of the ilium. and 6) the one I'm forgetting. Luckily, one or more 
prolacertiforms share these. 

Sticking points have been 1) the greatly elongated, not reduced finger four, 2) 
the extended, not reduced, toe five, 3) the pteroid, and 4) the prepubis, 5) 
multi-cusped teeth, none of which are shared by archosaurs. Luckily, one or 
more prolacertiforms share these.  Your friend's paper will have to consider 
these lists. Make sure that they do.

To help you out, I have a complete list of revisions to my 2000 paper if your 
friends would like to add ammo to their cannon. I'll send it to whomever you 
wish. Science marches on.


DU: I shall therefore be 
sticking to what I believe to be the most precise statement it is 
possible to make at present about pterosaur origins: 'there are several 
options available and not one of these is more clearly preferable than 
any of the others'. Coding cladistic data sets for the ingroup 
relationships of pterosaurs on the basis of only one of these hypotheses 
(be it prolacertiforms, ornithodirans, or basal archosaurs) would be a 
mistake. 

DP: David, did you not agree with some of the coding I presented? If so, 
perhaps we could compare notes on specifics? I am, and always have been, 
available for discussion. The coding was not on the basis of a hypothesis. It 
was on the basis of examining the fossil.

Finally, you'll have to tell me someday what happened to your interest in 
Prolacertiformes? You twice lectured on Sharovipteryx and the pterosaur 
connection. Were you knocking it? I'll have to hear more about these abstracts:


Unwin, D. M. Sharovipteryx: what can it tell us about the origin of pterosaurs? 
48th Symposium of Vertebrate Palaeontology and Comparative Anatomy, Portsmouth, 
England, Monday 28 Aug. - Sunday 3 September. 


Unwin, D. M. Sharovipteryx and its significance for the origin of the pterosaur 
flight apparatus. 5th European Workshop on Vertebrate Palaeontology, 27.6.2000 
- 1.7.2000, Staatliches Museum für Naturkunde Karlsruhe (SMNK) Erbprinzenstr. 
13 D-76133 Karlsruhe Germany

Sincerely,

David Peters
St. Louis

PS. Something in the latest Prehistoric Times (not a peer-reviewed pub.) is 
germane to the subject. Lots of pictures.  Get it at Prehistoric-Times.com