Pternary pterosaurs (was Karlsruhe azhdarchide)

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

Pternary pterosaurs

David Peters wrote:

'Saw the charts at SVP. The people I talked to noted that most of the
pterosaur cloud was in the bird cloud'

Which I pointed out in my talk, emphasising that the birds in that part 
of the cloud include penguins, frigate birds, swifts etc. a group not 
noted for their terrestrial ability.  


'and that it was heavily weighted
toward Solnhofen specimens (a fairly normal bunch).'

So what! As I emphasised we had almost complete coverage at the family 
level and this is what was important.


' Did not see
Pterodaustro (big feet), Anhanguera (tiny feet)  or Pterorhynchus,
Huanhepterus or BPM0002 (all small femora) in the cloud. Could be there,
just missed it.'

How could you 'see' them. They were not labelled. Pterodaustro and 
Anhanguera were there. Pterorhynchus was not there, but falls in the 
upper part of the cloud, Huanhepterus is very poorly preserved and 
neither I nor others who have seen the specimen can confirm much about it 
other than the cranial details, BPM0002 also falls in the upper part of 
the cloud.   



' Perhaps Dr. Unwin could tell us if they were included.
Is so, Dr Unwin has made his point.'

Point made then...


'The pterosaur cloud is smaller. If
not, then let's see what the bird cloud looks like when one removes the
oddball birds, the flamingoes and lily pad walkers.'

Has no effect. In fact, as I described in detail in the talk, you can 
reduce the bird sample to just a hundred points (from the 350 or so we 
used) and you get almost exactly the same cloud shape, its just thinner.


'Jim Cunningham may wish to weigh in on this subject since the hind limbs
may have acted as elevators in pterosaurs, which brings up the
possibility that aerodynamic efficiencies may have restricted
dimensions, rather than dermal connections.  Birds tuck in, both in the
air and on the ground, so comparisons may have little functional
cross-correlation.'

Sure, we can speculate about this for ever, so I prefer to stick with the 
hard data and what I can actually see in the fossils regarding the wings. 


'Dr. Unwin also noted that in birds the tail is separated from the hind
limbs by a reduction of the caudofemoralis muscle group and all of its
associated anchor points.'

I claim absolutely no originality for this. See all the stuff that Gatesy 
and Middleton did, and countless other comments in the literature before 
that. 

'However, he did not note asimilar decoupling in pterosaurs and all of 
their attenuated tail
precursors. Of course bats are not comparable in this regard at all, 
having reacquired a coupling dermis long after the demise of the 
caudofemoralis complex in their cynodont predeceosors.'


In this respect pterosaurs and bats are remarkably similar: fore and hind 
limbs structurally and functionally coupled, but tail decoupled from that 
complex. Interesting that the morphospace they occupy is almost identical 
in volume.  


'Dr. Unwin showed a sampling of purported deep wing membranes, including
the famous super-clawed "azhdarchide"  (metacarpal  and fingers + hind
limb) from Karlsuhe with an interesting stain bisecting the slab.' 

Being a traditionalist I went and actually looked at the specimen a 
couple of times, and even used a microscope. It has a beautifully 
preserved cheiropatagium with superbly preserved wing fibres and a clear 
line of attachment running right down the crus to the distal end of the 
tibia. 

One additional point. Grant Hazlehurst also found a very strong 
correlation between fore and hind limb lengths in his morphometric study 
of pterosaurs (Hazlehurst, G. 1991. The morphometric and flight 
characteristics of the Pterosauria. PhD Thesis, University of Bristol). 
This is exactly as in bats, but quite different from birds where there is 
no real correlation. Grant's work is not the same as the study we did on 
the hind limbs, but obviously ties in very neatly with it and is 100% 
consistent with fore limb- hind limb involvement in the flight apparatus. 
Sadly it has never been published.
 
Cheers,

Dave








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David M. Unwin PhD

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)
0049 30 2093 8868 (fax)
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