Re: Quetzalcoatlus mass

["Mark Witton" <Mark.Witton@port.ac.uk>]

Mike's knocked it right on the head: the Q. n. body in Don's paper is 1.8 m 
long! Depending on the pterodactyloids used, I get body length estimates for Q. 
n. of between 0.65 and 1.3 m: some rough calculations suggest that Don's 544 kg 
is brought down to c. 240 kg and 300 kg, respectively, when these body lengths 
are taken into account. These figures conform much more with the work of Greg, 
Jim and I (though the latter is obviously still a bit higher, but at least it's 
in the same ball park. Well, the car park outside the ball park, anyway). 
Interestingly, I found Q. n. had a volume of 500 litres when I measured it in 
clay, and that was a _bulky_ Quetz. Don's estimate requires it to have an 
overall body density of 1.1 g/cm^3, which is pretty amazing for an animal with 
such an extensively pneumatised skeleton. 

Speaking of which, I'm still not sure about applying avian densities to 
pterosaurs: large pterosaurs may have relied on being just a little less dense 
to achieve their large size (it's almost certianly not a coincidence that the 
largest pterosaurs are the most pneumatised). It's reasons like this that I 
think regressing masses from a skeleton - which I think could be made far more 
sophisticated and accurate that I managed - is a good way forward.

Not to end on a downer, though, Don's paper contains some real good stuff and, 
importantly, is extremely thorough in its presentation of methodology. Plus, 
it's great to see that 'heavy' pterosaurs are becoming in vogue: this is a real 
step forward from where someone giggled at the mention of Paul's 250 kg Q. n. 
mass at the Flugsaurier meeting!

Mark

--

Dr. Mark Witton

Palaeobiology Research Group
School of Earth and Environmental Sciences
University of Portsmouth
Burnaby Building
Burnaby Road
Portsmouth
PO1 3QL

Tel: (44)2392 842418
E-mail: Mark.Witton@port.ac.uk
>>> Mike Habib <habib@jhmi.edu> 21/05/10 10:50 PM >>>
Two other quick notes on the pterosaur mass paper I forgot before:

1) limbs are likely way too thin for most species, esp Anhanguera and  
Quetz. Would be fun to have Henderson re-run with better limb  
reconstruction, because it would greatly change the percentage plots,  
too (which I am really happy he included, incidentally)

2) I was a bit disappointed at the throwaway comments regarding mass  
and launch limits based on living bustard and goose launches. This  
happens in many papers, and is both subjective and inaccurate.  
Obviously I'd argue that reference to quad launching would be good  
there, but I may be ever so slightly biased.

I think I am actually done now....

--Mike H.


Sent from my iPhone

On May 21, 2010, at 5:00 PM, Mike Habib <habib@jhmi.edu> wrote:

> I have just finally done a full thorough read of the paper: some  
> great work, nicely written, and very transparent. However, the Quetz  
> model is significantly inaccurate, which explains the mass issue:  
> torso is much too large. Not Don's fault, he was using the  
> measurements from the classic 1981 and 1990 papers, but they are out  
> of date in this regard. Most of the other models look really good,  
> though. Wings are probably far too broad across the board, but  
> that's not the thrust of the paper.
>
> Cheers,
>
> --Mike H.
>
>
> Sent from my iPhone
>
> On May 21, 2010, at 4:34 PM, Mike Habib <habib@jhmi.edu> wrote:
>
>> I am in agreement with Greg Paul on this one. It is worth noting  
>> that Greg P. , Jim Cunningham, and Mark Witton all derive roughly  
>> the same body mass estimates for giant pterosaurs, using three  
>> different methodologies (in all three cases, the methodology works  
>> on extant species for confirmation).
>>
>> At a quick glance, it seems that the slicing technique is basically  
>> overestimating at large sizes - hence it seems to work for living  
>> birds alright, and animals near that size range, but accumulates  
>> error at large body sizes. The methods used by the three authors  
>> above, by contrast, were verified on larger animals.
>>
>> Incidentally, Quetz was probably a long-distance flyer, just not by  
>> continuous flapping flight.
>>
>> Cheers,
>>
>> --Mike H.
>>
>>
>> Sent from my iPhone
>>
>> On May 21, 2010, at 4:10 PM, GSP1954@aol.com wrote:
>>
>>> I was the first to explain that Quetzalcoatlus was far more  
>>> massive than
>>> the conventional wisdom. I was in charge of the restoration for Paul
>>> McCready's robotic QN project and quickly realized that the  
>>> skeletal framework was
>>> way to big to accomodate the human-like 70 kg mass thought  
>>> necessary to
>>> achieve flight, and I published more realistic weights starting in  
>>> 1987 in Nature.
>>> As one who thinks superpterosaurs were real massive the new  
>>> estimate of
>>> about a half tonne is a real stretch. The half size Q. sp are  
>>> sufficient to get
>>> a reasonable volumetric estimate, and scaling up from that results  
>>> in a
>>> quarter tonne for Q. northropi assuming a normal avian specific  
>>> gravity. The
>>> existence of what appear to be fully developed wings on the  
>>> superpterosaur
>>> indicate it was a true flier, albeit perhaps a short range burst  
>>> flier. A
>>> number of researchers including myself have shown that the span/ 
>>> mass ratio was
>>> simialr to some gliders and there was plenty of muscle power to  
>>> take off.
>>>
>>> GSPaul</HTML>