Re: Chaoyangopteridae

[jrc <jrccea@bellsouth.net>]

----- Original Message ----- 
From: "GUY LEAHY" <xrciseguy@q.com>
To: <jrccea@bellsouth.net>; "Michael Habib" <mhabib5@jhmi.edu>
Cc: <dinosaur@usc.edu>
Sent: Monday, June 02, 2008 9:01 PM
Subject: RE: Chaoyangopteridae



> What about long necked birds such as swans and flamingos? Swans in 
> particular are interesting in this regard, since they not only exhibit 
> large >tracheal dead space but are known to fly at considerable altitudes.

Swans have relatively larger torsos and lungs, and relatively shorter necks.

> I regard endothermy and its resulting elevation of aerobic power as an 
> essential precondition to the development of powered flight.

It's not required as a precondition for soaring flight -- only contiuous 
flapping flight.  There's no evidence that pterosaurs developed flapping 
prior to soaring.  Nor any evidence to the contrary either.  And, there is 
no requirement for substantial aerobic power in flap-gliding mode.  A 
soaring animal has the option of flapping in short, anaerobic bursts, 
repeated only when atmosperic lift is temporarily unavailable and after 
sufficient recovery time.

> I don't believe it's any coincidence that all living vertebrates which fly 
> have both. .......Ectothermic flyers would be highly at risk for fatigue 
> during >flight,

Not if their primary mode of flight was dynamic soaring.

> and metabolic recovery between flights would take much longer than an 
> endotherm of comparable size.

Not necessarily.  Odds are that an ectothermic soaring animal would land 
after a period of soaring, and would be able to anaerobically launch again 
immediately, if need be.  That said, note that I believe the earliest known 
pterosaurs were endothermic.

>  Plus, fatigue during flight might have certain survivability 
> consequences... :-)

If they aren't flapping during flight, why would they fatigue?
JimC