Re: Pterosaur size

[don ohmes <d_ohmes@yahoo.com>]

----- Original Message ----
From: jrc <jrccea@bellsouth.net>
To: d_ohmes@yahoo.com
Cc: dinosaur@usc.edu
Sent: Wednesday, December 13, 2006 12:38:55 PM
Subject: Re: Pterosaur size


----- Original Message ----- 
From: "don ohmes" <d_ohmes@yahoo.com>
To: <dinosaur@usc.edu>
Sent: Wednesday, December 13, 2006 11:13 AM
Subject: Re: Pterosaur size


> But then you would (wager they will eclipse Quetz)? I wouldn't. Unlike Jim 
> and Mike, I don't think today's environment could evolve a Quetz-sized 
> volant.

------- Why not?  Current atmoshperic conditions wouldn't stress either them 
or any of their ancestral line.......

You keep telling me that, but I'm skeptical. Wingstroke amplitude and landing 
speeds are 2 reasons why. The trend I see in the fossil record is another. Your 
statements about launch modes are interesting, your knowledge base is evidently 
comprehensive, and for all I know you are right. But I am still skeptical. Like 
I said, it is an opinion. Too bad we aint got a few million years, because I 
have been known to place a bet.

> Or tomorrow's environment either.

_____That triggers a real big "Why not".

The physical properties of the atmosphere constrain many processes, including 
flight. It is my opinion that a slow directional change in the physical 
properties of the atmosphere provides the best fit for the fossil record as a 
whole.  In my opinion, the direction is such that "tomorrow" (say, 10 mys) will 
be even less pterosaur-friendly than today..

> In fact, I think the current size limit for flapping flight is below 
> Argentavis, and somewhat above the largest birds living...

---------I tend to agree with this particular statement, but what do avian 
limits 
have to do with pterosaurian (or bat) limits?

Actually, you don't agree, except as it applies strictly to birds. I meant to 
include bats and pteros. See below.

> even considering that some systems are superior to others, which to my 
> mind just increases the variance, but doesn't affect the slope of the 
> moving average. Just an opinion.

------------Some of us don't see a moving average in operation.

But it is there. You may feel that it is irrelevant, and you may be right to 
dismiss. But it is there.
Largest volants in time sequence: Q. n, various pseudodontorns, A. mag, 
Pseudodontornis, T. incredibilis, T. merriami, California Condor.
In wing span sequence: Q. n, A. mag, various pseudodontorns, Pseudodontornis, 
T. incredibilis, T. merriami, California Condor.
 If you accept that the trough after K/Pg is caused by a catastrophic event, 
and smooth accordingly, you get a distinctly non-fluky looking curve that is 
~100 mys long, without need for any statistical manipulation whatsoever. The 
negative correlation of wingspan to time (past to present) is better than -.95. 
Corrections appreciated. I find it compelling. But that is just my opinion. 
Correlation is strong even if you punch in some of the comeback kids 
post-K/Pg...


> Drosophilids optimize wingload in a few generations, in response to 
> latitudinal changes.

-----------------Individual birds do it in a few days, in response to changes 
in wing area 
because of the moult.  Birds that lose, say 30% of their wing area during 
the moult also tend to lose about 30% of their body mass (which does reduce 
their efficiency, but also allows them to continue to fly without much 
alteration of performance). 

Yes. Although that is not morphic optimization in the evolutionary sense.

Don