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Re: New bird /pterosaur flight paper in PLoS ONE



I'm also far behind on literature, but do not see big problems with
such a hypothesis. Accepting the possibility large azhdharchids did
not fly (hypothesis which I do not dare to support or refuse to
support because of ignorance) I also think that all flight
specializations may be just explained by descent from volant
ancestors, and not usefulness in the actual giant.

2009/4/30 Simon M. Clabby <dinowight@yahoo.co.uk>:
>
> Can I just play devil's advocate for a minute, and probably show how far 
> behind with the literature I am?
>
> Let's say large Azhdarchids are too big to fly. Is it possible that when 
> younger they can fly about, doing aerobatics and so on, but after their 
> mating years are over, they keep growing, and flight becomes more difficult, 
> until one day they are grounded permanently? From this point, then enter a 
> terrestrial phase, scavenging from smaller predators kills, before either 
> starving or falling prey to a large predator.
>
> Maybe the maths is wrong in this study (which it almost certainly is), and 
> the upper limit is higher, but would my idea be completely ridiculous?
>
> Simon M. Clabby
>
> --- On Thu, 30/4/09, Mark Witton <Mark.Witton@port.ac.uk> wrote:
>
>> From: Mark Witton <Mark.Witton@port.ac.uk>
>> Subject: Re: New bird /pterosaur flight paper in PLoS ONE
>> To: dinosaur@usc.edu
>> Date: Thursday, 30 April, 2009, 10:59 AM
>> Hmm... this is an interesting
>> conclusion. I remember an article in New
>> Scientist from a while back about the same thing: I don't
>> remember being
>> convinced about their conclusions of pterosaur mass and
>> flight then, and
>> the paper's done little to change my mind. Here's the
>> beef:
>>
>> 1) This is all based on 'albatross-like animals', but
>> plenty of
>> pterosaurs were nothing like albatross in wing shape or
>> body
>> proportions. Capping a limit on maximum flight mass based
>> on one very
>> derived group of birds would be like scaling-up a skink to
>> estimate the
>> maximum masses of sauropods: they're different beasts, and
>> shouldn't be
>> treated so interchangeably when it comes to scaling.
>>
>> 2) There are craploads of pterosaurs with wingspans
>> exceeding the Sato
>> et al. maximum flighted wingspan (5.1 m) that are clearly,
>> clearly
>> flighted animals. Pteranodon springs immediately to mind: 6
>> - 7 m
>> wingspan, thousands of individuals found hundreds of miles
>> out to sea,
>> enormous, seabird-like wings for soaring flight, all the
>> appropriate
>> swells and crests around their shoulders f
> diddy-little hindlimbs rendering them pretty cumbersome on
>> land...
>> There's evidence that other ornithocheiroids were of
>> similar size, and
>> plenty - maybe most - azhdarchids were even bigger and
>> still retain
>> flight-characteristics of robust humeri, huge deltopectoral
>> crests and
>> all the rest of it. Sato and chums need to explain why
>> these chaps
>> retain so many characters related to flight but exceed
>> their maximum
>> theoretical wingspan: they suggest their conclusions
>> support an
>> excellent piece of work saying that some pterosaurs may
>> have been
>> terrestrial foragers, but this idea does not apply to all
>> pterosaurs at
>> all, nor explain why even the biggest azhdarchids retain
>> attributes
>> indicative of flight despite being over twice their
>> theoretical
>> wingspan.
>>
>> 3) I don't quite see how they can justify their 93 kg mass
>> for
>> Pteranodon and 274 kg estimate for Quetzalcoatlus: neither
>> has
>> particularly procellariiform-like proportions and yet,
>> again, Sato and
>> friends only use this group to extrapolate masses for these
>> pterosaurs.
>> My own estimates for Pteranodon and Quetzalcoatlus based
>> on
>> extarpolations of bird mass are 60 and 150 kg, respectively
>> - quite
>> different from their procellariiform-alone estimates. Once
>> again,
>> pterosaur morphological diversity has been ignored in
>> favour of a
>> dogmatic view that they were all marine bird-like soarers.
>> This is even
>> more perplexing because the authors like the idea of some
>> pterosaurs
>> living inland and being strongly terrestrial in their
>> habits: they are
>> aware that marine-dwelling and continentally-dwelling birds
>> have very
>> different wing shapes and flight styles, right? So how can
>> they start
>> talking about the maximum masses of a pterosaur group that
>> appear to
>> live predominately inland? Sheesh.
>>
>> I guess I could go on about the general lack of
>> consideration for all
>> sorts of recent work on pterosaur mass and flight (they
>> could really do
>> with a copy of Mike Habib's Zitteliana paper,
> nce
>> - how can
>> they explain the stupidly-robust humeri of big pterosaurs
>> if they're
>> doing little more than standing around on them?), but it
>> would be very
>> rambly and moany, so I'll stop there. Bottom line: not very
>> impressed
>> with the results or methodology. If I can be bothered, I
>> might write a
>> proper rebuttal. In the mean time, I should really get on
>> with some
>> genuine work. That said, the university cafe is offering
>> free food...
>>
>> Mark
>>
>> --
>>
>> Dr. Mark Witton
>>
>> Research Associate
>> 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
>>
>>
>>
>> >>> Andy Farke <andyfarke@hotmail.com>
>> 29/04/2009 21:33 >>>
>>
>> Sato K, Sakamoto KQ, Watanuki Y, Takahashi A, Katsumata N,
>> et al.
>> (2009) Scaling of Soaring Seabirds and Implications for
>> Flight
>> Abilities of Giant Pterosaurs. PLoS ONE 4(4): e5400
>> .
>> doi:10.1371/journal.pone.0005400
>>
>> Abstract:
>> The flight ability of animals is restricted by the scaling
>> effects
>> imposed by physical and physiological factors. In
>> comparisons of the
>> power available from muscle and the mechanical power
>> required to fly,
>> it is predicted that the margin between the powers should
>> decrease
>> with
>> body size and that flying animals have a maximum body size.
>> However,
>> predicting the absolute value of this upper limit has
>> proven difficult
>> because wing morphology and flight styles varies among
>> species.
>> Albatrosses and petrels have long, narrow, aerodynamically
>> efficient
>> wings and are considered soaring birds. Here, using
>> animal-borne
>> accelerometers, we show that soaring seabirds have two
>> modes of
>> flapping frequencies under natural conditions: vigorous
>> flapping
>> during
>> takeoff and sporadic flapping during cruising flight. In
>> these
>> species,
>> high and low flapping frequencies were found to scale with
>> body mass
>> (mass*0.30 and mass*0.18) in a ma
> chanical flight models (mass*1/3 and mass*1/6).
>> These scaling relationships predicted that the maximum
>> limits on the
>> body size of soaring animals are a body mass of 41 kg and a
>> wingspan
>> of
>> 5.1 m. Albatross-like animals larger than the limit will
>> not be able
>> to
>> flap fast enough to stay aloft under unfavourable wind
>> conditions. Our
>> result therefore casts doubt on the flying ability of
>> large, extinct
>> pterosaurs. The largest extant soarer, the wandering
>> albatross, weighs
>> about 12 kg, which might be a pragmatic limit to maintain a
>> safety
>> margin for sustainable flight and to survive in a variable
>> environment.
>>
>> Available for free download at:
>> http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0005400
>>
>>
>> Andy
>>
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>
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