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Re: Fw: ptero endothermy



Mike Hanson wrote:
> 
>   
> According to Witmer, Chatterjee, Franzosa & Rowe, 2003, pterosaurs were
> porbably superior fliers in comparison to birds and I don't think a
> crocodile-like metabolism would be sufficient enough.

In terms of flight mechanics, power production, and flight 'style', why
not?

> According
> to John Conway (http://www.pterus.net) pterosaurs has thick coats of hair
> (ptero-feathers, as I will call them from now on) as well as fat for
> insultaion (as well as aerodynamic streamlining)

Don't bet on the fat.  John's sketches of fat and streamlining were a
consequence of a chat he and I had about fat in pteroaurs and places to
put it.  keep in mind that any fat stored on the torso or neck have to
be supported by the shoulder musculature and bone structure.  Fat stored
in the wings (for example, behind the elbow), is span loaded and allows
a substantially lighter structure at the shoulder, so may be
advantageous.  There is presently no strong support for either venue, or
even for substantial fat storage of any kind in pterosaurs.  John is a
wonderful source of insight on pterosaurs, but some of what he says,
like all of us, is intended to be speculative (John, if I've stuck my
foot in your mouth here, please shout out).

And don't bet on extensive 'fur' on all pterosaurs either.  There are
substantial areas where it is unlikely that the big ones could afford
it.  Personally, I think it most likely to occur on the shoulders and
near the aft part of the neck, but have not attempted to either prove or
disprove that.  I seriously doubt that any would ever be found on the
wings, with the possible exception of some selected portions of the
underside of the innermost wing where seperated flow is most likely to
occur.

> Thet's where Conway's theory comes in also. He says that
> fat and a thick coat of hair would also help with aerodynamics in
> steamlining the animal.

They very possibly could have that effect, in selective areas.  Keep in
mind that the fat would burn off during a long flight, modifying the
streamlining effects through the course of the flight.

> Also, so far there are no and have been no animals
> that have or had scales and also had self-powered flight.

Ever look at a bird's lower leg and foot?

All in all, I think you make some good points.

Jim