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Re: Sharovipteryx - delta-winged glider? ?don't think so.



Lots of points:

First of all, with all due respect to the authors, why was this paper
written? And who were the easy umpires? I note that the only
illustration the authors provide is a cartoon in the style of past
cartoons. Why won't anyone [else] attempt a detailed tracing of
Sharovipteryx? It's one of the best preserved fossils of all time, down
to the skin.

Dyke, G.J., Nudds, R.L. and Rayner, J.M.V. Flight of _Sharovipteryx
mirabilis_: the world's first delta-winged glider. Journal of
Evolutionary Biology (Online Early)

They found no forelimb parts, yet like Gans, et al. 1987, their
hypothesis predicts and needs a canard of some sort. I found a complete
forelimb on both sides. And so did others (unnamed for the present
because their paper is unpublished). If you want to see the forelimbs
they're traced at:

www.pterosaurinfo.com > taxa > Sharovipteryx.

All the arm parts can be added to the cladogram without perturbation.
Although trailing edge membranes are not visible in the fossil, they are
visible in sister taxa: Longisquama and pterosaurs. So IMHO there's a
_probable_ canard and a definite set of forelimbs provided with tiny
centralia which have migrated to the leading edge where they come to be
known as pteroids. And pteroids are useful for that anterior membrane,
the propatagium which aids in flight.

Say you dispute the presence of forelimbs and a canard? That's ok.

Then you've got that wonderful and quite visible wrinkled neck skin,
which at rest is 6x wider than the cervicals. Large
hyoids/ceratobranchials invade the foreparts suggesting that if the neck
skin is stretched even further laterally you've got some wonderful
strakes, ala in the gliding snake, fully manipulable by the elevation
and depression of the cervicals. In pterosaurs that's all the cervicals
are capable of, elevation and depression. [Just to avoid confusion and
argument, pterosaurs did not have strakes. Those disappeared with
short-necked Longisquama]. So the elements of pitch control are already
present and the delta canard need not be imagined.

With regard to the possibility of flapping hindlimbs, I'll leave that to
you all, but consider that the fossil is preserved with hind limbs
outstretched laterally, and with such tiny forelimbs, this was an
obligate biped. Going from one configuration to the other was aided by
newly formed prepubic bones and a newly solidified pubis/ischium
depressing the wings/legs (_at least_ so they could be used as landing
gear!) , opposing a greatly elongated ilia above, aided by aerodynamic
lift, perhaps acting to passively elevate the wing during the flight
stroke. So up and down can be accomplished.

An interesting lizard. Answers alot of questions. Solves alot of
problems. Too bad others aren't spending enough time with it.

More on Sharovipteryx in the latest Prehistoric Times (another shameless
plug), including images of the newly found crushed skull parts.

David Peters
St. Louis