Saddle up me high horse (was pterosaur wings)

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

Saddle up me high horse ostler, I'm a ridin' out: 


In response to my challenge: 

>So, where is the fossil evidence for a narrow wing? Is anybody, anywhere 
willing or able to
> cite a single specimen in support of this idea? 

Peters wrote:

>Yes. Me. By the end of the year, I am told by the editorial staff.

And the name of the taxon? Specimen number? 



Later, I inadvertently wrote:

> Pterosaur tracks are now known from more than 30 localities ranging from the 
late Middle
> Triassic

Doh! That should of course have read late Middle Jurassic. 


With regard to pterosaur terrestrial ability Peters wrote:

>>Imagine Nyctosaurus _trying_ to walk quadrupedally. The wings are _so_ large 
relative to everything else, that those distal metacarpals hit the ground 
_beyond_ the tip of its beak. It would be like a child trying to walk 
with grown-up crutches.<<

First, I reject the argument that because Peters finds it difficult to 
imagine Nyctosaurus walking quadrupedally that somehow the whole idea of 
pterosaur quadrupedality is flawed. As Martin Lockley is fond of saying 
'Tracks don't lie', and I think we all agree that the 1000's of tracks 
already found all show pterosaurs proceeding quadrupedally with 
plantigrade feet. 

Secondly, Bennett (1997, JVP tracks paper) has already published an 
excellent reconstruction of how Nyctosaurus might have stood and walked 
in a quadrupedal fashion supporting itself on the wing-knuckle (please 
ignore digits i-iii, apparently Nyctosaurus didn't have them). Moreover, 
impressions of the manus at various track sites show that the 
wing-knuckle often contacted the ground. Yet another example of good 
correspondence between skeletal anatomy/functional morphology and tracks. 


Sarah Sangsters work

Peters opined:

>>At the time Sarah was only familiar with Clark's work which was dismantled 
by my subsequent paper on hinge line analysis Peters 2000 (Ichnos 7(1): 
11-41) where I showed a model of a dimorphodontid pes in a digitigrade 
pose that did not violate Clark's dictum on metatarsophalangeal line 
extension. <<


Unfortunately, it would appear that pterosaurs were not familiar with 
Peters (2000) hinge line analysis and, as the tracks show, doggedly 
continued to proceed in plantigrade fashion. Well, to be fair to 
pterosaurs, the construction of the joints in the pes completely prevents 
hyperextension and digitigrady as Clark et al convincingly demonstrated 
in their Nature paper, so, even if pterosaurs had known about the 2000 
study, they still could not have managed digitigrady. 

More importantly, according to Sangsters' presentation at SVPCA earlier 
this year, one of the primary goals of her work on Dimorphodon was to 
test the various ideas that have been published regarding the stance and 
gait of this pterosaur on the ground. This she has done, for example 
using computer based approaches to establish the centre of mass and its 
relationship to the hind limbs (way, way in front of the feet - 
bipedalism practically impossible), and concluded that Dimorphodon was a 
quadrupedal plantigrade. To state that 'At the time Sarah was only 
familiar with Clark's work' is not just wrong, its highly misleading and 
makes imputations regarding Sangsters work and understanding of 
pterosaurs that are unwarranted and offensive. 


Bennett's website:

I am a (proud) Mac owner (G3), using rather outdated software (Netscape 
4.08) and had no problems at all accessing Bennett's website and viewing 
all the images. (Incidentally I completely agree with Bennett's 
conclusions). So, one might ask, how is it that a computer based graphics 
artist, using a machine, software and knowledge of computer graphics that 
I have no doubt are vastly superior to mine (no irony or sarcasm 
intended) was unable to view the images on the same site? 

More seriously, no one can have failed to notice the numerous 
exhortations by Peters, in his previous posts, that I provide 
drawings/photos of specimens or reconstructions to illustrate the various 
points that I have made and, since this debate is taking place in a 
public arena open to all (well, all with computers and web access), that 
I make these images publicly available. All credit to Bennett therefore 
for responding so splendidly by presenting a clear, well argued and 
profusely illustrated critique of Peters' claims based on computer 
enhancement of published pictures. So, why is it, now that we have some 
illustrations that we can all see and comment on, that Peters, who made 
the loudest demands for exactly this state of affairs, should immediately 
insist that images be removed from the web site, thus preventing any 
proper public debate? If this discussion regarding what can or cannot be 
seen in fossils (started by Peters' 'Roadkills' thread) is to remain in 
the scientific realm the pictures should stay on the site. The 
alternative, as Chris suggests in his conclusions, is that if these 
figures are unable to withstand public scrutiny then we must reject them 
and any conclusions based on them. 

OK, ostler, see that this horse gets some feed, and mind its head as you 
go in the stable. 

Tschuess

Dave 



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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)
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