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RE: Did dinosaur wings evolve for breeding display?/Longisquama



Dave Peters wrote:



  In the holotype specimen, the structures appear arranged in a radial fashion 
with some elements overlapping partially only on their "distal" extremities 
(for lack of a better term when inferring doubt as to their origin), and 
moreover the most "posterior" of these is positioned in such a way that it 
overlies where on a complete skeleton the posterior half of the torso, hips, 
and base of the tail might/would be. This implies at least some 
distortion/dislocation has occured on the specimen should these be 
integumental, and that some, if not most or all, are not in life position. But 
that's a LOT of speculation.



  I still have a copy of one of your speculative reconstructions with outline 
restoration. Without passing judgment on that image, I can argue that what the 
holotype shows are a row of irregular, semi-trapezoidal structures along the 
posterior margin of the forearm, which at least marginally resembles the 
condition in *Crocodilus*, and therefore any referral of this structure and arm 
design to a "wing" is a fair bit close to being fanciful. It takes the 
speculative restorations I have seen (not just by you, Dave) to derive a 
wing-like arm, and that massive speculation is not based on the raw data that 
is the slab, the skeleton, and the associated structures. Such a short arm, 
with such short structures would be about as capable of flapping flight as my 
arms with a hoodie on, and *Longisquama* has a proportionately bigger body to 
arm length than I do.

  I prefer, of course, studying what the skeleton tells us. As such, my 
skeletal restoration is rooted on the bones as preserved:

http://upload.wikimedia.org/wikipedia/commons/a/a1/Longisquama_insignis_skeleton%26silhouette_small.jpg

  Here I reconstructed the skeleton based only on the bones (although the 
unknown proportions and posture are based on a basal ornithodire, which is 
almost certainly wrong at this point) and there is a lot of doubt as to the 
structure of the bones of the snout (as the skull is crushed and distorted). We 
know VERY little about this due to the fact that a single crushed, incomplete 
specimen with poorly preserved surfaces makes for determination difficulties.

  Cheers,

Jaime A. Headden

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