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Pteroid



All,

Well, it took a bit longer than I had hoped but I have finally uploaded picts of the hand/wind of my latest model, Rhamphorhynchus.

The images can be viewed at:
http://www.triunecommunications.com/fossilsmith/intheworks.html

I would love to hear any comments as at this point all is up for change, thanks to Jim, Dave, John, and Nick for the comments to date... I hope I used them well.

Sincerely,

Allan D. Smith
Fossilsmith Studios
http://www.fossilsmith.com




From: "James R. Cunningham" <jrccea@bellsouth.net>
To: "Peters, David - Learning" <Dave.Peters2@maritz.com>
CC: john.a.conway@gmail.com, npharris@umich.edu,fossilsmith@hotmail.com
Subject: Re: pteroid, OFFLIST
Date: Thu, 19 Oct 2006 10:16:03 -0700

To all, some comments inserted.  I notice that my e-mail composer has
screwed up the formatting, so you may have to extract my comments by
context (sorry for that).
Jim

Peters, David - Learning wrote:

>  Functionally I'm a passive pteroid guy.

Swinging the wrist aftward will swing the pteroid from medial to
antero-medial position.  This is a flutter control mechanism.  Swinging
the pteroid back to the medial position will swing the outer arm forward
and help hold it there, but that needs to be active.  Based on markings
on the Quetz pteroid and LDC, I'd say that it probably is active.

> Like in bat and bird propatagia.

The pterosaur wing has somewhat different needs.

> Maybe some dorsoventral movement in flight, to change the leading
> edge,

A little, but mostly medial to antero-medial.  A little leading edge
camber modification goes a loong way.  The real need is to control the
chordwise tension in the wing membrane, to keep the aeroelastic number
from falling below the bistable limit during flight at lower lift
coefficients.  And to swing the outer wing fore and aft.

> but otherwise not much.

I have sort of the converse opinion.  They could get by without the
dorsoventral movement -- they can't get by without the antero-medial.

> Really that area is a minority part of the wing

It is critical to flutter control in both the inner and outer wing.  It
is not minor.

> and if the bird guys (ref. below) are right, then the tendon in the
> same place in birds prevents over extension of the elbow due to drag
> forces in flight. Sounds logical and sufficient to me.

Wing drag forces in flight are fairly inconsequential throughout most of
the flight regime.

>  I'm also a stiff wrist,
>
> ----- The quetz wrist is highly mobile, and must be for flapping
> flight.  It is also quite robust, in both types of Quetz.
>
> non supinating forearm guy.
>
> ----- If I'm interpreting you correctly, keep in mind that the forearm
> must  suppinate and pronate (driven from the shoulder) in order for
> flapping flight to work effectively.
>
> IMHO, the pterosaur hands could clap its hands, grasp a tree trunk (or
> a female during union), and flap but that all involves the free
> fingers facing ventrally when abducted, medially when adducted.
>
> ----- The free fingers never face ventrally, they aren't oriented for
> that.
>
> With those restrictions, the fingers naturally fall into the pterosaur
> hand print ichnite when quadrupedal. Allan, send pix if you want to of
> your progress.
>
> ----- They also fall into the handprints in the configuration I
> prefer.  Plus, they match the preserved hand position of Paul Sereno's
> Nigerian pterosaur.
>
>  John, can't help you with the  'tranversus palmaris and flexor digiti
> quinti in pterosaurs'  but I agree that the big finger is the fourth,
> as in arboreal lizards. The fifth is still visible in Cosesaurus,
> Longisquama and MPUM 6009 and there is no break in the morphology
> going back to Huehuecuetzpalli, the Cretaceous relic, and
> Macrocnemus.The following reference has drawings of Eudimorphodon' s
> carpus from various angles and can be cited for pteroid origin and
> original usage hypotheses.Peters, D. 2002b. A New Model for the
> Evolution of the Pterosaur Wing -- with a twist. - Historical Biology
> 15: 277-301.
>
> Hope this helps and share with the DML if you wish.
>
> David Peters
> Dave.Peters2@Maritz.com
> davidrpeters@earthlink.net
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