Re: Chaoyangopteridae

[Michael Habib <mhabib5@jhmi.edu>]

> I do not know if it would have sufficient muscle mass to generate the 
> accelerations required, but if it did,  the skeleton could withstand 
> them.

Based on my launch model, which places 20%+ of the animal's total mass 
in overall forelimb musculature, and about 17-18% in the hind limb 
(including extrinsic muscles at the hip), the power should have been 
sufficient for the given accelerations.  However, this assumes that 1) 
the forelimb muscle mass is highly anaerobic (expected for a large 
flyer, but obviously not known) and 2) there is some modest elastic 
storage in the forelimb tendons.  In reality, my estimate here is a bit 
conservative, because I don't allow the animal much above 120% elastic 
storage.  That may seem high, but dedicated jumpers (such as galagos 
and frogs) get 700%+ in combined elastic and counter-movement pre-load 
advantage.  Given the length of the pterosaur forelimb, and several 
specific features of the osteology, I suspect that pterosaurs probably 
managed a fair bit of preload (better than I'm giving them).

> I think Mike Habib prefers a somewhat lighter weight (about 80%) with 
> about 3/4 as much wing area (in other words, the same wing loading).  
> His scenario can get off the the ground without overloading.

Yes, that's indeed what I tend to use (note that Jim means 80% of the 
weight, not 80% lighter).

> My methods are structured to give an average weight.  I believe that 
> both Darren's/Mark's and Mike's estimation techniques are structured 
> to give maximum weights. (Guys, correct me if I'm wrong....)

You are correct again - my technique is definitely structured to give 
maximum weight; Darren/Mark's should do the same based on my 
understanding of their model.  There are advantages to estimating 
maximums, but we also have to be careful with how they are used (and 
not assume that the animal flew near maximum weight all the time).  I 
choose that approach in part because I am interested in mechanical 
limits, and this is obviously maxima oriented.

Cheers,

--Mike H.


Michael Habib, M.S.
PhD. Candidate
Center for Functional Anatomy and Evolution
Johns Hopkins School of Medicine
1830 E. Monument Street
Baltimore, MD 21205
(443) 280 0181
habib@jhmi.edu