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Re: questions for Witton & Naish: Azhdarchid Pterosaur Functional Morphology
I've not read the paper yet (Darren sent it to me this morning, and I've
been busy -- will get to it this afternoon or evening) so, I'm only going to
make a few general comments herein. See below.
----- Original Message -----
From: "Mark Witton" <Mark.Witton@port.ac.uk>
To: <email@example.com>; <firstname.lastname@example.org>
Sent: Thursday, May 29, 2008 9:57 AM
Subject: Re: questions for Witton & Naish: Azhdarchid Pterosaur Functional
The mesotarsal ankle of pterosaurs dictates that the knee joint has to be
perpendicular to the long axis of the body
The quetz ankle doesn't indicate that. However, on the ground, the knee
would be a lot closer to anteriorly oriented than laterally (doesn't
and the tibia has to be orientated more-or-less subvertical.
On the ground when walking, I agree. With some emphasis on the 'sub' part
of subvertical. The tibia can be moved well away from the vertical, but
likely not to the extent of a sprawling gait.
With this in mind, we can see from the orientation of the Haenamichnus
footprints that the trackmaker was walking with its knees facing forward,
I haven't seen those tracks (or, if I have, I've forgotten), but based on
the pterosaurs I'm familiar with, I would not expect the knees to face
laterally when walking.
If this is the case, the femora cannot be splayed out to meet them, or
else the trackway would need be much wider to maintain a vertical-ish
This seems to imply that the femora cannot be splayed out in flight, and I
strongly disagree with that, but am likely misreading the sentence above
and will withold any real comment till after reading the paper and
discussing it directly with Darren and Mark
Azhdarchids have long femora, after all: they would need a considerable
case of rickets to stick their femora out, strut around with a splayed
gait, and bring them back into Haenamichnus territory.
I think they can stick their femora out more than you may credit them with,
but probably not to the extent of splaying the feet on the ground.
"W&N illustrate: pteroids in the anterior orientation and a deep chord
wing membrane. Is there any evidence for either?"
I can stick my hand up and admit that the pteroid orientation is probably
not correct: the drawing and science behind the drawing were done
pre-Bennett's 2007 efforts. If I re-did this bit now, I would go with
Bennett's medial orientation. Just for the record, though it only has a
minor effect on wing area and therefore doesn't change our conclusions.
I haven't read the conclusions yet, so can't comment on conclusions right
now -- but, the pteroid articulation does have a pretty substantial effect
on wing performance. That said, I too agree with Bennett's medial
orientation. However, the range of motion that is available from that
medial orientation is capable of generating substantial aerodynamic
effects.both locally and throughout the wing, since among other functions,
it is capable of changing the spanwise tension and camber of the wing all
the way to the wingtip.
The evidence for broad wing membranes is discussed in the paper, and I'm
not going to go through it all again. I know some folk have their reasons
for not buying broad chords, but I (along with Darren and, I think, a
healthy chunk of the pterosaur community) reckon it's the way the evidence
I'd say ya'll are in the majority. Since all three major configurations
will work after a fashion, my bet has always been that over the eons, all
three have existed at one time or another. I wish the fossil evidence were
better. Till better fossil materials turn up, we're all speculating to some
Firstly, Fig 9 is a effectively an elaborate sketch and should not be
taken as gospel: it has scientific backing, but, as with any bit of
palaeoart, there's a certain amount of artistic licensing. The folding of
the membrane is something I've always struggled with, so and I really
wouldn't put to much faith in my restoration on that issue.
That's candid, and I'd cut Mark some slack on that.
"But didn't Kellner and Langston show with Q. sp. that the dentary is
shaped much like a flattened and squared-off yardstick?"
All jaw tips refered to Azhdarchidae, including Azhdarcho, Bakonydraco,
Quetzalcoatlus and some scrappy bits from Morocco, have flattened occlusal
surfaces and steadily tapering lateral margins.
That's not true of the lateral margins of the quetz anterior lower mandible
Not sure about Jidapterus: the mandible is preserved in dorsalvental view,
sure, but it's also squashed flat.
and I've been called stupid in several comment sections on newspaper
websites in the last few days.
You know, that's one source of insults that should roll off us like water
off a duck's back.
"Is this the only possible configneck could have risen more vertically?
Should a range of motion be provided?"
Yeah, it should be, but there aren't many azhdarchid cervicals around that
articulate properly: they're all squished and deformed in the wrong
I woudn't say that they all are, but I would agree that it would be better
if fewer were..... :-)
Hence, while we can get a sense of the neck's immobility, actually
quantifying it is easier said than done.
We reckon there's more dorsoflex than ventral because the condylar
articular surfaces face posterodorsally, suggesting the vertebrae did not
regularly arc downwards significantly. There is, however, more flex
apparent at the anterior end: the posterior is locked up pretty tight. No
actual figures for you on this though, I'm afraid. Maybe Wann Langston
will have had better luck with his studies on Quetzalcoatlus sp.
He did. But, I'm going to leave comments about it to him.
"I would also suggest a range of motion for the knees. For if the knees
bent more than indicated then the posture changes."
Y-e-s... but we're basing our posture on footprints.
I think the footprints may say more about effective orientationsthan they
do about possible orientations. Without the cartiledge, its hard to tell
what the range of knee articulaton was, but based on the skeleton alone,
it is obviously substantial.
Pterosaur femora are also, if you come from our school of pterosaur wing
membrane construction, integral to the wing shape. Hence, their functional
roles are twofold: supporting a pterosaur on the ground _and_ in the air.
Hence, their articulation is not necessarily going to be straightforward.
Femur orientation in the air for both scenarios would have been much the
same most of the time, whether the wing membrane attached to the hindlimb or
not. There are scenarios where the orientation would be different, but in
either event, the articulation is NOT straightforward.
"As above, sprawling femora, when combined with knees bent at 90Â still
place the feet beneath the torso."
But not with the feet oriented as per trackways evidence.
Still not with you on the sprawling thing. Besides, pterodactyloid pelves
and limbs are not really built to support a sprawling limb:
I agree. When you direct the femur outboard, the tibia is directed aft or
laterally in the horizontal plane, not down.
..... Such a structure is noticably absent from sprawlers. Pterodactyloids
have the same kind of anteriorly projected illiac blade as birds and
mammals, and therefore probably didn't sprawl.
I agree, though there is also another reason that you don't mention. The
iliac blade defines the camberline of the wingroot.
"The illustration (Fig. 6) fails to show individual toes. And if the toes
are considered as a whole, they are aligned parallel to one another, not
much wider than the metatarsal set. So I was wondering how webbing was
discovered? If it could not be confirmed by the authors, shouldn't they
have questioned it?"
Gotta read the paper before I can comment.
Well, maybe. To our shame, neither Darren nor I could afford a trip to
Korea to see the Haenamichnus prints,
Darn, I thought I was the only one who had that problem :-)
I disagree. With the possible exception of the Chaoyangopterus-like
critters from China, there's nothing else really like an azhdarchid out
I'm not sure that I would agree with that just yet.
No reason for it: just got carried away. Too much fuzz. The pterosaur, not
Oh. In that case, I won't send you a razor.
All the best,