Re: Pterosaur size (Was: Great in the air, not so good underwater)

[jrc <jrccea@bellsouth.net>]

----- Original Message ----- 
From: "Michael Habib" <mhabib5@jhmi.edu>
To: <dinosaur@usc.edu>
Sent: Monday, December 11, 2006 6:37 PM
Subject: Re: Pterosaur size (Was: Great in the air, not so good underwater)


> Yes, the 120 kg estimate seems very high.  A 120 kg volant bird might be 
> possible, but it would depend greatly on the ecotype, launch mode, and 
> planform (all of which are interconnected).

As you say, it would depend upon all the above.  Argentavis could barely get 
off at 75 Kg.  I have trouble imagining a 120 Kg volant bird.
> > PS-- How big would a ptero or bird have to be to elicit a "OK, these 
> > guy's had to have had some help, because there is just no way in standard 
> > atmosphere..."? Actually a serious question.
>
> Jim already pitched in on this for pterosaurs (far better than I could). 
> For birds, it depends a great deal on the planform and launch mode 
> involved (which will be related to ecotype, etc).  Using the scaling 
> relationships I have for pseudodontorns (and the bone strength ratio model 
> I've been using for their mass estimates lately), I would cautiously list 
> about 75 kg as the rough limit.  (The largest species actually known seems 
> to fall around 60 kg).  For continental, convective soarers (ie. 
> Argentavis like forms), the limit in standard atmosphere would be 
> substantially higher (probably over 90 kg), but I can't say much at the 
> moment.

I'd want to look closely at launch technique for a 90 Kg bird.  Once 
launched, I think they'd be able to sustain flight OK.  I mention in 
passing, that Qn and all similarly sized pterosaurs are far, far more 
robustly constructed than Argentavis magnificens.

Jim