Re: The Peters Strikes Back (pterosaurs)

[david peters <davidrpeters@earthlink.net>]

Darren Naish wrote:

-- Wing membranes. At the moment the bulk of the 
evidence indicates that extensive wing membranes are more 
likely than narrow-chord ones. 

>> A bulk of evidence would be great! But I'm looking for one example. 

I am particularly impressed 
by data showing a correlation between fore- and hindlimb 
lengths: this is Elvidge and Unwin's data (see new JVP 
abstract volume, p. 48A). 

>> You can have fore and hindlimb correlation and also have a decoupled wing.

As usual, I know that anecodates 
don't count for much, but I have seen an unpublished 
(azhdarchoid) specimen at Karlsruhe which appeared to 
show an extensive wing membrane. 

>> Then someone in Karlsruhe gets the steak dinner. Get us together! I'm 
>> metaphorically holding my breath, but previous such examples have not proven 
>> valid. I am _not_ being sarcastic when I say: I would genuinely like to see 
>> a deep wing membrane. And a pteroid sticking out anteriorly insitu. And a 
>> plantigrade dimorphodontid track. And a pterosaur egg. (Wouldn't we all!) 
>> Evidence is what it's all about. 

I am far from convinced 
by your interpretations of specimens as shown in, e.g., your 
_Historical Biology_ paper. Let me emphasise to you 
(again) that I have gone into the whole pterosaur issue 
open-minded and without any original preference for any 
particular view of pterosaur life appearance and phylogeny. 
Unwin did cast a few spells and utter some subliminal 
things down the telephone but they didn't sway me...

>> I appreciate your open-mindedness. What didn't convince you?

But the point alluded to in the quote is 
that, so far as we know, pterosaurs did not radiate as miriad 
passerine/microbat-like forms.. in other words there is 
"Little indication that pterosaurs radiated as small forms of 
terrestrial environments, as both birds and bats did". Ok 
there are anurognathids and whatnot but, well, I don't think 
you can reasonably disagree with this statement.

>> I wasn't thinking in terms of aquatic versus terrestrial. Thank you
for clearing that up for me. And not to be argumentative here  -- while I agree 
that there does 
appear to be a definite tie to the water in non-dimorphodontids, 
that still leaves a number of dimorphodontids (and their numbers are 
increasing!)

-- Quadrupedality vs bipedality. Sorry Dave, while I'm 
happy for facultative bipedality in pterosaurs, assorted lines 
of evidence show that quadrupedality is presently better 
supported. The lizards you cite do not have the same CoG 
problems that the pterosaurs do. 

>> What sort of ptero/lizard CoG problems are you referring to? Perhaps we 
>> could 
address these issues?

Your implication that 
people in this generation (whatever that means) are ignoring 
what you say is unfair: people might be disagreeing with 
you because you might be wrong, not because they're 
blinkered or stupid.

>> The problem might be that no one has argued against 
my hypotheses, either privately (in my presence) or in press. I gave a damn good
argument that, although it came out of an unexpected an overlooked corner,
it answered a lot of questions. So I'm left wondering... (is it my breath?)

-----------------------------
Hind limb diversity: compare big-footed Pterodaustro to 
tiny-footed Anhanguera.
-----------------------------

Entirely valid BUT pterosaur hindlimb diversity is still 
lower than that seen in decoupled birds. That's the point.

>> You're assuming that pterosaur hind limbs are coupled. Hind limb diversity 
>> -- or
_any_ kind of statistical analysis might not show that. Only _evidence_ can 
show that. 


Re: pterosaur ancestry, yes personally I agree with you that 
prolacertiforms appear to be the most likely ancestors of 
pterosaurs. But more data is still needed for us to be 
confident about this and I note that some pterosaur workers 
are still luke-warm to the idea. 

>> Why is this so? What's the counter-argument? What's the better hypothesis? 
I'm totally in the dark on this. I _know_ it's not Scleromochlus.

I do not however agree with 
your interpretation of prolacertiforms as dinosaur-like 
bipeds.

>> Only to the extent that, like little dinosaurs, they could run bipedally. 
>> From a distance, if 
you weren't able to determine the greater sprawl of the femora, you might 
mistake one for
a little dinosaur. 

-----------------------------
Re: _Cearadactylus_ nested with ctenochasmatoids...

-----------------------------
This should have been Dr. Unwin's clue that this could not 
be true.
-----------------------------

Ah, you have magic powers too? I thought the purpose of a 
cladistic analysis was to produce results based on data, not 
to show what is intuitively most satisfying.

>>> The results are from my own cladistic analysis, Darren. Almost 180 
>>> characters and 90+ taxa. And
I've often seen that when something doesn't seem right, it needs to be further 
investigated. I understand
Dr. Unwin's situation more than you might realize, however. The most difficult 
part of the pterosaur cladogram
to figure out is the basal pterodactyloid situation. I struggled a long time 
with the problem until it all crystalized. 
And I'll send you the data, if interested.



-----------------------------
Re: While virtually nothing is known about
pterosaur reproduction

> This will be known soon.
-----------------------------

Err, yeah. Having seen the evidence for your pterosaur 
babies Dave all I can say is.. good luck convincing 
everyone else.

>>> While some embarassing over enthusiam did occur early on, the quest did 
>>> turn up 
some valid results in the past few weeks -- that you haven't seen. No one bats 
1.000.  
And, hopefully to my credit, I acknowledged those early errors.

All the best and, hey, no hard feelings:)

>> It'll all come out in the wash. I'm having too much fun to quit. Will you be 
>> at SVP? I'm sure you
don't want to miss out on the fun when I reveal the Chinese vampire to a 
disbelieving crowd.

>>>David Peters

-- 
Darren Naish
School of Earth & Environmental Sciences
University of Portsmouth UK, PO1 3QL

email: darren.naish@port.ac.uk
tel: 023 92846045