Re: Gliding vs Non-gliding

["Marcel Bertolucci" <mbertol@zaz.com.br>]

    As I can see, the biomechanics of mammals and reptiles differ from one
another, mostly because of the metabolism and the energy necessary to
biomechanics of flight. That's maybe why mammals do have representatives
that fly and others that glide, and the reptiles may only glide.
    Regards,

        Marcel Bertolucci
    ( mbertol@zaz.com.br )
DINOWEB BRASIL:
http://www.geocities.com/CapeCanaveral/Campus/7472/index.html
"Dinosaurs are the most interesting and amazing mystery of nature!"


----- Original Message -----
From: "Tim Williams" <twilliams_alpha@hotmail.com>
To: <mbertol@zaz.com.br>; <dinosaur@usc.edu>
Sent: Friday, April 27, 2001 4:56 PM
Subject: Re: Gliding vs Non-gliding


>
>
> Marcel Bertolucci wrote:
>
>
> >     I think that, at least, we've to compare _Icarosaurus_ or
> > >_Longisquama insignis_ to modern (co-)relatives, like the "flying
> > >dragon"(_Draco volans_), a reptile with some sort of membrane beside
>his
> >chest that allows him to glide. Not that we cannot take mammals, >for
> >instance, but it would be better taking reptiles to compare to >extinct
> >reptiles.
>
>
> No.
>
> The most important factor to consider here is biomechanics, not phylogeny.
>
> _Icarosaurus_ (and other kuehneosaurids), _Coelurosauravus_ and the modern
> _Draco_ glide(d) by a membrane supported by rib-like extensions of the
axial
> skeleton.  (In _Coelurosauravus_ these rib-like struts are of dermal
origin;
> in kuehneosaurids and _Draco_ they derive from the thoracolumbar vertebral
> column).  An analogous behavior has been hypothesized for the dermal
> appendages of _Longisquama_; the evidence is not as convincing.
>
> As such, all these reptiles are pleural gliders.  Their gliding membranes
do
> not involve the limbs.
>
> It has been forcefully argued (by Ruben and Feduccia, among others) that
> _Megalancosaurus_ possessed a gliding membrane suported by the forelimbs,
> hindlimbs and possibly the tail.  This is a patagium.  Modern gliding
> mammals glide by way of a patagium.  So (possibly) did _Sharovipteryx_;
the
> fossil specimen shows an impression of what appears to be a uropatagium.
>
> As such, modern mammalian gliders (such as flying squirrels and
phalangers)
> are more relevant to inferred patagial gliding in _Megalancosaurus_ than
the
> "rib-wings" of _Icarosaurus_ and _Draco_.
>
>
> Tim
>
>
> ------------------------------------------------------------
>
> Timothy J. Williams
>
> USDA/ARS Researcher
> Agronomy Hall
> Iowa State University
> Ames IA 50014
>
> Phone: 515 294 9233
> Fax:   515 294 3163
>
> _________________________________________________________________
> Get your FREE download of MSN Explorer at http://explorer.msn.com
>
>