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Patagium attachment Was: Re: Pterosaur.net



M. Hanson wrote:
Lately I'm seeing claims made like this, and this quotation from the 
Pterosaur.net site has piqued my interest:
"The more basal, paraphyletic “ramphorhynchoids” had a broad uropatagium that 
linked across the two hind limbs. By contrast, the pterodactyloids had a 
uropatagium that was split, such that a roughly triangular membrane ran along 
each hind limb [figure 3a]. The uropatagium would have had several uses during 
flight."
This seems to imply that the uropatagium did not attach to the tail. I am 
wondering where the evidence for this comes from. It seems that the only 
specimen that could potentially be interpreted as having a free tail is the 
Sordes pilosus holotype, however, there is a peculiar fold down the centre of 
the patagium that could be interpreted as the region on which the tail 
originally attached, and due to decay it fell off. 

>>>>


For some reason a group of pterosaur experts have been applauding this sort of 
nonsense lately (pterosaur.net; Unwin, 2004). Sad.
You're right, Mike. The uropatagia were split, as in Sharovipteryx and 
Pterodactylus [phylogenetic bracketing tells us that if not good ole 
observation].

Dr. Witton has an interesting take on this:

http://www.flickr.com/photos/markwitton/4010200611/in/set-72057594082038974/

a bit of both worlds here. Uropatagia attached to the tail, but narrow span 
wise, so much so that the elongated fifth toe is attached at its tips only 
millimeters from the tail. Don't try to walk in this configuration! Suggestion 
for Mark, extend the hind limbs out like horizontal stabilizers on a small 
airplane. Add more meat to those thighs to match the extent of the ilia. Remove 
pedal digit V from any interaction with the uropatagia. Remember Tanystropheus, 
Langobardisaurus and Cosesaurus have a homologous digit V and they didn't fly. 
No pterosaurs preserve the uropatagia in association with digit V.  Digit V is 
commonly found folded upon itself, which ruins any membrane that can be 
imagined there. Finally, when you extend the hind limbs quite a bit laterally, 
there's another bad situation that develops with regard to attaching the 
brachiopatagia at the ankles, so follow John Conway's model, and the example of 
every known brachiopatagium in the fossil record and attach the big wing 
proximally at the anterior mid-thigh. Suddenly everything will make sense and 
you'll be One with Nature.

In contrast with the preceding example, here Dr. Witton goes the other way and 
attaches the uropatagia to each other:

http://www.flickr.com/photos/markwitton/149392935/in/set-72057594082038974/

with digits V pointing medially (ouch) and framing the uropatagium trailing 
edge. I've always wondered in this configuration where the cloaca emptied. If 
above the uropatagium, then the poor thing is constantly soiling itself and to 
get rid of the accumulated guano, must clean itself like a contortionist. If 
below the uropatagium, then there's no traditional tetrapod sex. They will have 
to "do it" bonobo style. 

Best to just split the uropatagia. It solves so many problems! Shift that 
paradigm!!!

David Peters

 (additional queries answered below)


Also, I am interested in how the long bony struts in the final caudal vertebra 
of Pteranodon is interpreted if the tail is unattached.
Additionally, what would be the aërodynamic implications of a free tail?


>>>>

No uropatagia are preserved with Pteranodon. Considering the fragility of those 
tail bones, I would guess they were unencumbered. 

Minor if small. Less minor if elongated. The tail vane, while decorative, would 
have acted like arrow vanes in keeping the tail aligned with the direction of 
flight.