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Re: New bird /pterosaur flight paper in PLoS ONE



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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