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

[MICHAEL HABIB <habib@jhmi.edu>]

> >  Quetzalcoatlus northropi, by comparison, could easily have exceeded 
> 200 
> > kg, and likely more than that).
> 
> Qn could have flown at that weight, but it would not have been an 
> optimal 
> loading for the planform.  About 150 Kg, seems more probable.

Gotcha; that seems reasonable.  I was going for the upper end (full fuel load, 
etc) to make the point about how much of a mass difference we might need to 
account for.


> I think the mass difference between birds and pterosaurs may have been 
> 
> closer to 2 fold.  I agree about the load jump, and note in passing 
> that 
> modern birds often depend upon aerobic power for the muscles (with the 
> 
> exception of launch and perhaps short periods of hover with the 
> flutter 
> stroke).  Pterosaurs don't appear to have quite that dependence 
> because of 
> the intermittent flapping (yes, I realize that many birds are 
> intermittent 
> flappers too).

I've also noted that aerobic power tends to be the norm for most birds during 
steady state.  Use of anaerobic power during launch can be very important, 
though, especially in birds in which anaerobic burst launch is actually the 
primary flight mode (galliforms especially).  As for intermittent flapping, 
there are only a few groups of living birds (ie. soaring specialists) that can 
utilize intermittent flapping to the degree that large pterosaurs could.  Both 
the convective soaring groups and marine soaring groups of modern birds 
inherited a mostly aerobic power system from their immediate ancestors.  It may 
be that they have secondarily derived higher anaerobic power, but I don't know 
if this has been rigorously studied or not.  Even among pelagic seabirds, I 
suspect only a few would really be under strong selection for greater anaerobic 
fiber ratios; albatrosses are the obvious ones.  Taxa like sulids would receive 
less of a benefit, because they really balance extended soa
ring with significant use of high-efficiency flapping gaits (especially very 
low-amplitude continuous vortex gaits).

> P.S.  I'm losing track of who is saying what too. 

Yeah, it gets jumbled very quickly.  Oh well.

Cheers,

--Mike H.