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Re: Flying giraffes



One more comment: it should be noted that the torso in the Quetz illustration 
is almost certainly too large. It is increasingly apparent that the torsos on 
big pterodactyloids were almost shockingly small.  Taking this into account 
yields an animal that is more plausibly in the mass range discussed by Greg and 
myself, but still about the same height as a giraffe.

Cheers,

--Mike


On Jun 20, 2013, at 5:36 PM, Mike Habib <biologyinmotion@gmail.com> wrote:

> Good comments all around, and I appreciate that my paper seems to be making 
> the rounds.  With regards to overall mass, I agree with Greg that a 200kg 
> mass (give or take) is reasonable for the largest known azhdarchids, perhaps 
> up to 260kg.  This is similar to the range that Greg originally suggested 
> years ago (in DOA, I believe) and that Mark Witton retrieves using his bone 
> mass scaling option.  I also get a similar result using a more flight 
> performance oriented approach that starts with a reconstructed possible wing 
> area (actually, a series of them).  The method provided by Henderson appears 
> to produce a mass in that range, as well, if the torso length is 
> reconstructed to proper dimensions: in Henderson (2010) the torso length for 
> Quetzalcoatlus northropi is probably too long by about 2.5 times, assuming 
> that the proportions were similar as for other azhdarchids.
> 
> It should also be noted that the Chatterjee and Templin volume did not really 
> estimate mass - they assumed that pterosaurs would have bird like features 
> and used this to calculate a maximum flight mass.  Given that answer, they 
> constrained possible body mass.  I naturally object to this method on 
> numerous grounds, two being that 1) max size is not universal (latest paper)  
> 2) direct body mass estimation is more sensible than their backdoor approach, 
> which makes many more assumptions.
> 
> Greg: you make an excellent point regarding the difficulties in scaling up Q. 
> sp. to form a Quetzalcoatlus northropi model.  However, as Jaime notes, Mark 
> gets rather similar results just scaling from a generalized azhdarchid body 
> plan.  The skull in the illustration is almost certainly too gracile; Mark 
> knows this but the image is an older one.  He and I have conversed a bit 
> about revised reconstructions using the skull material available from giant 
> pterosaurs and related taxa.  With any luck, this will occur down the line.
> 
> In terms of mechanical limits: I agree that airliner sized bioflyers are 
> probably impossible (material constraints), but overall I don't think it is 
> particularly informative.  My point with the paper is that because the limits 
> are morphology specific, there is no one global limit that we can really 
> calculate, and instead we must focus on local limits based on specific 
> morphologies.  There will be some limit where biological materials simply 
> fail, but I don't think it's particularly worth trying to estimate.
> 
> Cheers,
> 
> --Mike
> 
> 
> 
> On Jun 20, 2013, at 5:09 PM, Jaime Headden <qi_leong@hotmail.com> wrote:
> 
>> Greg, 
>> 
>>  I don't think this says anything that Mike Habib or Mark Witton don't 
>> already know. Especially regarding the mechanical scaling (iso- versus 
>> allometric) when it comes to adjusting a "Q." sp. ("Kyoo Spuh," as Darren 
>> Naish calls it) animal to the size of the wing in *Quetzalcoatlus 
>> northropi*, potential taxonomic variation is consdiered but, given lack of 
>> thorough description of "Kyoo Spuh" at the moment, difficult to ascertain. 
>> Scaling factors aside, morphology of the head, neck and limbs in azhdarchids 
>> tend to follow one another across a few size ranges, and my understanding is 
>> that Witton's illustration, and the giraffe-sized possibilities, is derived 
>> mostly from composing an animal like *northriopi* to *Arambourgiana*, 
>> *Zhejiangopterus* and *Hatzegopterus* -- some of which can push against that 
>> size. These suggest mostly that pushing them up to the scale of the 
>> *northropi* wing isometrically at least will result in an animal that could 
>> look a fair-sized giraffe in the eye.
>> 
>>  I would defer to them on the mass issue. volumetric mass estimates not 
>> using the displacement method seem far more reliable (Henderson, 2010), and 
>> it would be problematic to use the argument from disbelief to dismiss it; 
>> though other authors have found values around half the 500 kg mass, 
>> including yourself, using better adjusted properties, and Henderson has a 
>> revision of the mass estimate in the works. It should be noted that 
>> Chatterjee and Templin's meager 70kg mass estimate was used to presume that 
>> the higher mass of *northropi* would make it effectively flightless without 
>> strong headwinds (!), cliffs, or whatever, such a classical idea as t be 
>> absurd in its own right. Your statement, though seems to confuse this idea 
>> with Habib's, who was summarizing the topic.
>> 
>> Below are relevant papers that touch on or are explicit on the masses of 
>> flying animals and, especially, azhdarchids.
>> 
>> Chatterjee, S. & Templin, R. J. 2004. Posture, locomotion, and paleoecology 
>> of pterosaurs. Geological Society of America, Special Paper 376.
>> Henderso
>> al mathematical slicing. Journal of Vertebrate Paleontology 30(3): 768–785.
>> Paul, G. S. 2002. Dinosaurs of the Air: The Evolution and Loss of Flight in 
>> Dinosaurs and Birds. Johns Hopkins University Press, Baltimore.
>> Sato K., Sakamoto K. Q., Watanuki Y., Takahashi A., Katsumata N., Bost, 
>> C.-A. & Weimerskirch, H. 2009. Scaling of soaring seabirds and implications 
>> for flight abilities of giant pterosaurs. PLoS ONE 4 (4): e5400. (available 
>> for free at: 
>> http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0005400)
>> Witton, M. P. 2008. A new approach to determining pterosaur body mass and 
>> its implications for pterosaur flight. Zitteliana B28: 143–159.
>> 
>> Cheers,
>> 
>> Jaime A. Headden
>> The Bite Stuff (site v2)
>> http://qilong.wordpress.com/
>> 
>> "Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
>> 
>> 
>> "Ever since man first left his cave and met a stranger with a
>> different language and a new way of looking at things, the human race
>> has had a dream: to kill him, so we don't have to learn his language or
>> his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
>> Backs)
>> 
>> 
>> ----------------------------------------
>>> Date: Thu, 20 Jun 2013 19:38:17 -0400
>>> From: GSP1954@aol.com
>>> To: dinosaur@usc.edu
>>> Subject: Flying giraffes
>>> 
>>> About Habib's new paper in Biol Theory. I continue to object to
>>> illustrations showing pterosaurs as enormous as giraffes, based only on 
>>> some arm
>>> elements. Also we are probably getting the skull wrong.
>>> 
>>> There has probably been a big mistake made -- moi included. We have been
>>> assuming what has without justification been called Q. sp. is a half sized
>>> version of Q. northropi (seriously inadequate holotype by the way). Simply
>>> scale the former up and you have Q. n. But there is big pterosaur skull 
>>> material
>>> from the Javelina that is larger than that of Q. sp., and quite probably
>>> belongs to Q. n. That of course is the front portion of the skull 
>>> photographed
>>> in the 1991 Wellnhofer book. The chances that three giant pterosaur taxa
>>> were flittering about t
>> ere
>>> is no reason to presume that the smaller Javelina azhdarchid is even close 
>>> to
>>> being the same genus as Q. n. The robust snout is similar to that of
>>> earlier members of the group (the possiblity it represents a nonazdarchid 
>>> when
>>> there are no other such remains from the Maastrichtian is very dubious).
>>> 
>>> It is probable that the robust snout is Q. n. (need to know what level of
>>> the Javelina these things come from, though, and the time span of the
>>> formation). For awhile I used that rostrum on my Q. n. illustrations until 
>>> the half
>>> sized taxa skull lured me like the sirens onto the Rocks of the Chimerias
>>> (don't know if that version was published anywhere). But I did the posterior
>>> skull wrong because we did not have azdarchid posterior skulls to go on. I
>>> cannot do a rerevised version because I do not have the info needed to scale
>>> it to the Q. n. arm, partly because the cervicals that are said to go with
>>> the robust rostrum have never been published (that might not solve the cross
>>> scaling problem though).
>>> 
>>> There is no way a 70-100 kg mass pterosaur will work for the colossal
>>> humerus and arm of Q. n. The size disparity is absurd. But we cannot even 
>>> come
>>> close to presuming that we can just scale up the Q. sp. skull, neck, body 
>>> and l
>>> egs to Q. n. and assume we have a giraffe size beast with a super
>>> heron-stork head as long as a giraffe neck. Doing so probably misrepresents 
>>> the beast
>>> in height and form. The body mass probably was in the 150-250 kg range.
>>> 
>>> I was the first to point out that super pterosaurs were probably far
>>> heavier than thought. But these extreme restorations based on dubious
>>> extrapolations are probably misleading the public.
>>> 
>>> Tend to agree with Habib that the biggest pterosaurs known or that evolved
>>> may not be the biggest possible living fliers by a considerable amount. But
>>> there probably is some limit. Hard to conceive of airliner sized biofliers.
>>> 
>>> GSPaul
>>> 
>>> 
>>> </HTML>                                       
>