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

----- 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.