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RE: Did dinosaur wings evolve for breeding display?/Longisquama
--- On Fri, 4/17/09, Jaime Headden <email@example.com> 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
What you've just said is self contradictory. If everything originates in an
orderly fashion, where the torso, hips, base of the tail would be, then you
have no dislocation.
> 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
by that do you mean Sharov's rough drawing?
are a row of irregular, semi-trapezoidal structures
> along the posterior margin of the forearm, which at least
> marginally resembles the condition in *Crocodilus*,
by that do you mean a set of extra large scales that stick out a wee bit?
> therefore any referral of this structure and arm design to a
> "wing" is a fair bit close to being fanciful.
Given those parameters: yes. But are those parameters valid? No, after careful
> takes the speculative restorations I have seen (not just by
> you, Dave) to derive a wing-like arm,
Every arm is wing-like. They are homologs. What factors change the ordinary
forelimb into a wing-like one in your opinion?
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.
Never forget Dial's studies with young birds with small wings. Also the
previews to a new Disney movie, Earth, show a duckling 'parachuting' to the
leaf litter. Wing length is not as important as you imply. Especially when you
consider Longi's cousin: Sharovipteryx. Don't follow your preconconceptions.
Follow the fossils. Flapping doesn't necessarily mean flying, either. Birds
flap long before they fly ontogenetically.
> I prefer, of course, studying what the skeleton tells us.
> As such, my skeletal restoration is rooted on the bones as
As I recall, a fine piece of art. Comments follow on another email.
> 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.
You and I both gotta go with what we got. I think you'll be pleasantly
surprised when you see the skeletal tracing. It covers all the bases.
> Jaime A. Headden
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