Re: questions for Witton & Naish: AzhdarchidPterosaur Functional Morphology

[jrc <jrccea@bellsouth.net>]

Comments inserted after -- symbol
JimC

----- Original Message ----- 
From: "Mark Witton" <Mark.Witton@port.ac.uk>
To: <jrccea@bellsouth.net>
Sent: Thursday, May 29, 2008 1:20 PM
Subject: Re: questions for Witton & Naish: AzhdarchidPterosaur Functional 
Morphology


> Sorry - didn't explain that very well. It's more that sticking the
> femora out laterally it affects the postture of the rest of the limb,
> which then causes the feet to also face anterolaterally and the narrow
> gait to disappear.

--I agree.

> I was a bit hasty. I mean that it doesn't affect wing area a great deal:
> tucking it in a bit more doesn't suddenly transform azhdarchids from a
> vulture into a duck, basically.

--I agree, but note in passing that the pteroid can affect the gross 
brachiopatagium area more than it affects the gross propatagium area (by 
means of tension control).

> I agree to a point: with perhaps the exception of Sordes, there are no
> fossils that unambiguously show an ankle-attachment (or any other
> attachment for that matter). That said, I can think of at least seven
> specimens that ambiguously show an ankle attachment (there may be more),
> whereas a knee-attachment is only really supported by one (also
> ambiguous), and the hip-attachment has no fossil support at all. It
> seems to me that finding seven slightly dodgy examples is enough to
> think that we might have the beginning of a pattern. And, sorry Dave
> (Peters that is - lots of 'Daves' in pterosaur research), I think there
> are enough pterosaurs specimens with proximal regions of the
> brachiopatagia preserved to rule out an elbow attachment.

--I agree with everything except solid evidence for the beginning of a 
pattern.  I do note though that I've never seen a brachiopatagium with a 
trailing edge more than half the length of the humerus behind the elbow AT 
the elbow.  I've also never seen one that attaches and ends at the elbow 
itself and can't believe that they did so.  To me the humerus ratio implies 
a fairly narrow wing outboard of the elbow in all pterosaurs.

> True: it is a bit more parallel-sided than other azhdarchids, so it may
> have had a blunter jaw tip. Still, there are no real 'blade-like'
> azhdarchid mandibles (at least, not in my definition of 'blade-like' -
> your Rynchops-type, I suppose.

--Agreed.  I wouldn't see any need for a blade-like mandible.  The skimming 
scenario that I propose for quetz is very un-rynchops like, and there would 
actually be a disadvantage to a blade-like mandible for that scenario.

> Not to be confused with the Thalassodromeus-butter-knife-type).

--Understood.

> I'm not sure that I would agree with that just yet."
>
> Sorry: do you mean about the affinities of Chaoyangopterus and his chums
> to azhdarchids, or that there are other azhdarchid-like pterosaurs out
> there?

--I'm not presently at liberty to say, other than it has nothing to do with 
Chaoyangopterus and kin.  It isn't something that I personally am working 
on.