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RE: How Pelicans learn to fish



  I can agree with what Mike says below (whole post left intact), but only so 
far as a holistic approach goes. The problem is that each piece of an 
integrated set of studies is that they are studies, which are integratable. 
Looking at the whole from the pieces is a step in the process, rather than a 
approach for the project, and I think this is where we are losing "it" (where 
"it" is capital-S Science).

  Mike perhaps also mistook my use of *Pteranodon* in my previous posts, as I 
used this taxon to model an interpretive argument that conflicts with proposed 
arguments we've seen so far, and to contrast it to the model made for 
azhdarchids by the person I was responding to. In these, a holistic approach is 
taken, but selective use of data points and study detail impairs what can be 
said of the holistic whole (redundant, I am sorry). It is not that *Pteranodon* 
seems less likely to be a long-distance flier (so too azhdarchids, and this is 
even favored by Witton), but that terrestrialism, apparent favored preservation 
regimes, beak structure and cranial "appearance," and the supposed conflict 
with black-skimmer jaw morphology with a skimming lifestyle in any other animal 
dissimilar to it, mean only what they do to themselves, and are each subject to 
much controversy and debate. The authors simply placed them into a collection, 
and said "here: This means X, less likely Y." I argue that to get to Y, you 
need to have all that you argue for X to be more plausible than all 
alternatives (parsimony). In this case, I can argue that *Pteranodon* was a 
shore scavenger and that nodosaurs were deep-sea foragers.

  Paleobiology is an imperfect little-s science, because it is frought with a 
lot of a priori arguments that are assailable, and in such a case, we can only 
be as perfect as our data. I have argued with people on paleobiological 
subjects who resoundingly seem to believe in the subjects they argue, and it 
shows in their papers and blogs and books. Sometimes, it is merely a simple 
assertion on the subject of the supposed corollary of a physical feature to a 
behavior, and on this particular conclusions can be made more securely, because 
it is a "physical" feature, and a demonstrated behavior, and thus very, very 
true. sO I TEND T BUCKback ginst these typesof arguments, hoping their authors 
are more willing to look deeply at their arguments and how their beliefs (which 
are nontheless real) are affecting it, or using cautionary language. It can 
even be done more simply by being more data-oriented than narrative-oriented, 
to be about the capital-S Science than the theory that they want to argue.

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, 4 Nov 2010 14:25:37 +0000
> From: Mark.Witton@port.ac.uk
> To: qi_leong@hotmail.com; dinosaur@usc.edu
> Subject: RE: How Pelicans learn to fish
>
> Jaime,
>
> Briefly: I agree with you that biomechanics are important, but surely
> the best approach to take when considering the habits of an extinct
> animal is a holistic one where all available and relevant evidence is
> taken into account? To continue with our Pteranodon example, we can
> consider the number of fossils in the Niobrara that are clearly
> terrestrially-derived (a handful of dinosaurs, none of which, AFAIK, are
> complete) compared to the thousands of Pteranodon that, in many cases,
> are associated, complete specimens. I suppose it is possible that all of
> these individuals were washed out to sea along with the dinos, but the
> numbers suggest this is unlikely.
>
> And yes, there's the biomechanical evidence that Pteranodon was a
> supreme flier comparable in ability to soaring marine birds but, from a
> wing ecomoprhology perspective, inconsistent with what we would predict
> in a terrestrial flier. No-one has ever done detailed studies on their
> terrestrial limb mechanics (save for the work with Robodactylus, I
> suppose, but I have my reservations about that:
> http://pterosaur-net.blogspot.com/2010/10/pterosaur-books-to-know-and-love-part-2.html)
> but there are reasoned considerations in print that suggest their
> terrestrial ability was limited. These, coupled with the fact that we
> have marine fish as gut content of Pteranodon, suggests that the data
> points at a pelagic existence for this pterosaur.
>
> And while quantification of as many mechanical parameters as possible is
> good, I think we can all agree that some basic application of everyday
> mechanical experience can be applied to some fossils, too. We all know
> from day-to-day existence that, on the whole, small, thin objects will
> break easier than chunky, robust ones. We can therefore, at least on a
> qualitative, comparative level, say if the anatomy of some forms is more
> suited for one thing than another. Darren and I did this with
> azhdarchids and had our findings supported by the mechanical testing of
> Humphries et al. (2007) who used both qualitative and quantitaive
> mechanics to cast doubt on skim-feeding pterosaurs (and we looked at a
> lot more than the jaw joint of Rynchops, too boot). Hence, while putting
> numbers to mechanical observations is obviously desirable, but I don't
> think we should sell our own observations short.
>
> Finally, in my view, applying a strictly mechanical approach to fossil
> animals is a dangerous game. The sauropod examples you cite are a good
> example: our biomechanical models of sauropod necks differ drastically,
> as Mike Taylor has already pointed out, from what we see in living
> animals. Simply modelling animal bones as beams or whatever to assess
> their strength is one thing, but attempting to accurately model complex
> movements and postures when we barely understand the same in living
> animals is a little foolhardy, surely? What I particularly like about
> the Taylor et al. paper is that it concedes that there's still a lot to
> learn about how animals work: they suggest we really need to get up to
> speed with the likes of neck arthrology in modern taxa before we start
> seriously modelling those of fossil animals. In the mean time, they
> suggest applying rules of uniformitarianism and parsimony in their
> place, a finding I agree with entirely. It's not as clever as a detailed
> biomechanical analysis, but I reckon it's smarter.
>
> Right, hope that makes sense. Back to work.
>
> 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
>
> If pterosaurs are your thing, be sure to check out:
>
> - Pterosaur.Net: www.pterosaur.net
> - The Pterosaur.Net blog: http://pterosaur-net.blogspot.com/
> - My pterosaur artwork: www.flickr.com/photos/markwitton
> >>> Jaime Headden 04/11/10 1:14 PM >>>
>
> Mark and the List,
>
> I may have been too blunt in the first (or too subtle), so I will
> explain in a little more context.
>
> 1. In the Niobrara, all fossils are found in marine sediments. This
> includes all so-called terrestrial fossils, such as nodosaurs. Now, it
> may be arguable to infer some form of aquatic viability to nodosaurs,
> but for the most part the limb anatomy implies these taxa are firmly
> terrestrial, and yet they are all found in marine sediments. This is
> instructive for a variety of reasons, the first among them being that
> the Niobrara is exceptionally good at preservation, and that the second
> being that the environment is conducive to pulling nearshore or
> shore-based carcasses into waters several to a hundred kilometers from
> shore. This should be no different were the animal a nodosaur (an
> apparent terrestrial herbivore), a hesperornithiform (a bird with very
> limited flying ability whatsoever, and likely a near-shore denizen) or a
> pteranodontid.
>
> 2. Some researchers, when comparing taxa to one another, tend to look
> on an archetypal level, or a elemental level, separating their
> perspective for the forest or the tree, respectively. In this case,
> looking at an animal, we can attempt to assess it on the basis of a host
> of features that seem to look like animal X, or we take a specific
> feature -- element Y -- and see what animals A-Z have element Y, and
> base our comparisons on ecology (and sometimes evolution) on the basis
> of this comparison. In my rather not-so-humble perspective, the best
> model may be the one that derives a lot of the second into the first,
> comparing a host of elements into a broad spectrum of biology. This
> allows us to make a broad assumption for animal X to be like animal Z,
> because of elements A-Z.
>
> For the most part, I think a lot of the discussion on the paleobiology
> of birds, pterosaurs, and other taxa comes across as this third,
> reasoned approach. But as I may have occassionally pointed out on my own
> blog (below -- currently suffering from new computer syndrome, forgive
> me for not handling or updating recently), some authors have slipped
> into either the archetypal or the elemental model of comparison, and
> argued against the third, integrated model in some fashion, or to use
> the first to fight the second (and vice versa). This has included birds,
> pterosaurs, and various other archosaurian animals. My favorite retort
> is "Sauropods are not giraffes." So, too, are "Pterosaurs are not
> birds," "birds are not special," etc.
>
> 3. So, in this perspective, I casually alluded to some research and
> made a few very bold statements tied directly to these; both in
> challenge and in plaintive appraisal. This includes the argument that
> azhdarchids are preferentially terrestrial and were like maribou storks
> (from Mssrs. Witton and Naish), or that azhdarchid pterosaurs could not
> skim feed because one skim-feeder had a specialized jaw joint (Mssrs.
> Witton and Naish, again), or that sauropods were correctly highly
> elevated in their neck posture because a range of other, often quite
> much smaller animals have elevated necks (Mssrs. Taylor, Wedel and
> Naish), that birds are powered fliers, that *archaeopterys* is a
> devolving bird, and that as a bird must have been a powered flier (Mssr.
> Paul). I have been openly critical of many of these papers not on the
> basis of some special expertise or quality of work which is being
> rejected or that I can produce to reject, but on the basis of logic.
>
> My argument is plain: None of these have made direct assessment of the
> feeding or stature effects of each of the organisms involved, but
> through attempts at comparisons without direct examination of the
> functional concerns of the animals involved. Let's break these down, and
> I will conclude this long post.
>
> 4.
>
> A. Preferential, even exclusive, habitats of the locality in which a
> fossil is found is only indicative of the location in which said fossil
> was deposited; it does not always indicate place of death (this requires
> additional data), or even generalized preference of habitat (this
> requires a load of what amounts to ecological data, and that includes
> feeding traces, coprolites, any other -ite indicating a direct
> preference for food, etc.
>
> B. I understand the paper in question
> (http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0002271)
> lists out a large number of other features, but again these data suffer
> other problems, including comparing the jaw joint of an azhdarchid to
> that of *Rhynchops*(, and concluding the former cannot skim-feed -- this
> is only true if skim-feeding is defined as that thing which *Rhynchops*
> (and only it does), which is a logical problem that ignores any other
> possible model for the term or method of "skim-feeding." I don't
> actually know about the data to as large an extent as some of the
> particulars in the issue, but I take the issue of what is essentially
> indirect comparison broadly: The authors do not show that the
> specialized jaw of *Rhynchops* is required for skim-feeding in that
> manner (as, indeed, they remark on another bird that skim-feeds that
> lacks said specialized jaw anatomy), and this only tells me that the
> initial claim is merely doubted, but used as a hammer nonetheless.
>
> C. In a more interesting set of discussions, the posture of sauropod
> necks was presented in a long stream of public airings of disapproval by
> accredited scientists, all of whom are well-respected and knowledgeable
> of their preferential taxa, but little work in print on the subject.
> (http://www.app.pan.pl/archive/published/app54/app54-213.pdf -- PDF
> link, open at your peril!) is a paper on the conclusive argument that
> sauropod necks are like other terrestrial diapsid necks in that they are
> tended to elevate at or around 45 degrees, unerringly. This is
> problematic for three reasons:
>
> 1) The primary animals used in the analysis (the one used to
> demonstrate the incohesiveness of Stevens and Parrish Osteological
> Neutral Pose) is a mammal which, in a comment on SV-PoW!, Kent Stevens
> was agast at the authors comparing sauropod necks to that of a mammal
> (these differing in a large number of fantastically different ways,
> including the structure of the zygapophyses, the centra, the
> intervertebral discs, and in fact the very model of the suspension of
> the head from an proximally elevated system of muscles and tendons found
> nowhere else in diapsids -- some birds have a similar system, and
> include suspended necks, including of all things *Rhynchops*, fairely
> notable for the fantastic number of tendons that extend from several
> discontinuous series of cervicals between head and dorsum).
>
> 2) The extrapolation to a broad set of taxa across Diapsida, to show
> how universal the neck posture is (conceding that some organisms differ
> markedly due to habitat, namely, the aquatic kind).
>
> 3) That for some reason, size doesn't matter here, that sauropods
> having the largest, longest necks of any terrestrial animal alive or not
> has no influence on this contraint (especially as the largest
> terrestrial vertebrates alive have fantastically short necks and huge
> heads).
>
> None of this is supported through direct analysis of the sauropod
> cervical system, rather only through inferences of the animals upon
> which the study is based. We can support that the unusual neck anatomy
> of some sauropods (like dicraeosaurids) or the bizarre cranial form of
> *Nigersaurus taqueti* requires us to make careful such broad-stroke
> comparisons, and even more so when studies have been published that
> alter the envelope to which sauropods can extend their neck in extremes
> or safe levels of stress on the joints, and that these shift the numbers
> upwards (for *Brachiosaurus brancai* = *Giraffatitan*) or downwards
> (*Euhelopus zdanksyi*); analysis of different groups of very-long necks
> sauropods show that they differ broadly in cranial form and dental
> apparatus, providing us with a missing ecological signal the authors of
> the study may have used to calibrate their work; and finally, a
> potential rejection of the use of biomechanical modeling for the sake of
> broad-stroke painting of sauropods as ... well ... giraffes.
>
> (With due respect to the authors, though, they do make strong
> comparison to a (presumably domesticated) chicken, extending their
> practical testing of dry, bone-only cervical and cervico-cranial
> articulation to a mammal AND a bird, and unpublished and referenced work
> supporting a broader collection of living animals examined under
> radiological means.)
>
> D. Birds are awesome in their variety but, and in no due disrespect to
> bird watchers or ornithologist, they aren't that special. Some of the
> things they do may be, but recent semi-scientific work produced by a
> populoar author and illustrator and scientist has challenged various
> apparent biomechanical or straight up osteological comparative work with
> an argument that a wing-like limb must operate as a wing. This is an
> archetypal thought, extending back to Aristotle, reminding us that all
> Creation is special and particular, and that purpose is driven in form
> due to evolutionary need, or special force. It is argued, similar need
> from a similar plan should conserve the variety of derivatives possible
> in its efficiency (Law of Conservation of Energy and all). Lockely has
> recently published a few pieces making the argument that there is
> conserved archetypism in the animal kingdom, and that some biological
> trends are natural, such that large-headed, large-bodied theropods
> should look like tyrannosaurs. In that vein, Paul argues that
> *Archaeopteryx* looks like a bird, is a bird, birds can fly, thus
> *Archaeopteryx* can fly. Maybe not very well, but nonetheless.
>
> ***
>
> All of these arguments require logic that is missing. As a pragmatist,
> as a conservative thinker (moderate politically, liberal ideologically),
> and one with an eye toward biomechanics as MY field, I tend to look on
> the practical testing side of things, and I go about thinking how I
> would test all of these hypotheses, and I cannot using the processes the
> authors do. Again, practical. I want to examine the various forces and
> modeling that describes an organism's flying, broad across the spectrum
> of fliers, and examine where my particular organism (proto-bird or
> pterosaur) might most closely fit, then examine that in the context of
> what is really quite a large host of additional data, both phylogenetic
> and ecologic. If an animal is argued to hold its posture in a certain
> way, I ask "How long?" "Why?" "What else is it doing?" "How do I
> determine extent, range, and performance of said posture?" "Are there
> other viable alternatives?" Sadly, some do not ask these questions. I am
> exceptionally interested in one particular part of biomechanics, and
> that's the study of dietary systems and especially oral anatomy, so when
> I see a potentially vital part of the various questions of pterosaur or
> sauropod posture/feeding, and many of these questions are ignored or
> lost in a sea of what the authors may feel are vitally more important
> questions, I am bemused.
>
>
>
> So when I talk about terrestrial *Pteranodon*, it's really about using
> conclusions that have little to do with modeling the anatomy and
> ecology through as direct means as possible, but about pulling in the
> various little "signals" to put forward what is probably not a very
> likely theory; and were I to publish this, I might be more severely
> laughed at than is due the consideration. It is plausible, but unlikely.
> But plausible.
>
> To Mark Witton's credit and in no criticism of the others mentioned
> here, the first Witton/Naish paper mentioned above is a great paper,
> probably the best among the works I've so far talked about. It really
> does approach the question from a large number of angles, and I have
> little doubt to the methods' authenticity. Mark showcased his
> terrestrial-wtalker, sauropod-baby-killer theory in London earlier this
> year, and I am sure it got a large number of people interested in the
> subject of paleontology who may not have been so immediately intrigued
> before. But the problem therein is that this is a premise being
> chosecased without a substantive amoutn of data supporting it. When
> contesting the theory of jaw function, the authors do not actually model
> the jaw function, merely poke holes into a particular comparison and
> declared the argument null. This seems illogical, and it raises a red
> flag, as it did in all of these other works I've mentioned. I keep a
> quote by Medawar in my sig because it reminds me of this topic, that
> none of us are immune to bias to a particular perception or idea. The
> more we are aware of it, the better we are armed to fight it. This is
> what I think "science" is.
>
> 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, 4 Nov 2010 10:17:03 +0000
> > From: Mark.Witton@port.ac.uk
> > To: dinosaur@usc.edu
> > Subject: RE: How Pelicans learn to fish
> >
> > Jaime,
> >
> > Not sure about the ideas of terrestrialised Pteranodon: over 1200
> > fossils of it have been found in the middle of the Western Interior
> > seaway and, AFAIK, not one has been found in a terrestrial deposit.
> I'm
> > wary of using the sedimentological contexts of large flying
> vertebrates
> > as indicators of habits (though have done so in print in the past: I
> > think it can be done if we're careful) but Pteranodon really is skewed
> > towards marine settings: we're special pleading, big-time, if we want
> > this critter walking around on land.
> >
> > I can't see the bauplan of Pteranodon working too well for Pteranodon
> on
> > land, either. There's that massive overbite on the jaws that would
> make
> > eating anything small a real issue, and the slenderness of the
> Pterandon
> > skull wouldn't lend itself to large, feisty prey items (though your
> > point about the skull being enlarged for signalling may be right here:
> > the overbite is larger in presumed males). Plus, their limbs really
> > aren't adjusted for walking around: the forelimbs are so much longer
> > than the hindlimbs that their terrestrial movement would be far more
> > hampered than that of other pterosaurs. Probing isn't too likely in my
> > view: deriving the full benefit of their jaw curvature would require
> > sticking, in the largest Pteranodon, about 60 cm of jaw into sediment,
> a
> > big issue when the skull expands in all dimensions along the jaw
> length.
> > Plus, along with the problems of the overbire, the rostrum is very
> thin
> > but tall: sticking it into sediment may risk breaking it
> > (Dsungaripterus, by contrast, is a better candidate for a prober,
> having
> > shorter jaw curvature and a more robust, powerful skull). Hence, while
> > you're right about the sample size of Pteranodon gut content being
> small
> > (one confirmed case, plus some associated fish debris with some
> > skeletons that, possibly, could be mere marine detritus), I expect
> it's
> > probably representative of typical Pteranodon fodder: little fish
> > wouldn't tax the slender skull and could easily be grabbed from the
> > water column, a place where that overbite doesn't get in the way.
> >
> > 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
> >
> > If pterosaurs are your thing, be sure to check out:
> >
> > - Pterosaur.Net: www.pterosaur.net
> > - The Pterosaur.Net blog: http://pterosaur-net.blogspot.com/
> > - My pterosaur artwork: www.flickr.com/photos/markwitton
> > >>> Jaime Headden 03/11/10 1:51 PM >>>
> >
> > Or we can take a cue from another direction and say that because the
> > skull is deep and triangular, and looks like a stork, it was feeding
> on
> > larger, more selective prey than opportunistic fishing in this manner.
> > Small amounts of fish may mean not as much fish feeding, after all
> > (although I am sure we've only been able to derive limited information
> > from limited specimens in which limited amounts of gut contents are
> > known -- correct me if the sampling is much higher in resolution than
> > this). Perhaps *Pteranodon longiceps* was a terrestrial carnivore, as
> > Witton and Naish suggested for another very-large-headed pterosaur
> > group. Moreover, due to the massively outsized skull of
> pteranodontids,
> > one may assume that head-based strategies for prey acquisition were
> the
> > norm, and that in this realm of comparison that they were incomparable
> > to a large number of living taxa (including birds) making comparisons
> > problematic (just as the relatively inflexible neck of azhdarchids
> > impairs comparison to storks).
> >
> > One thing I do not recall (precisely, but may have seen in print
> > somewhere) is that the slight upturn to the beak and the outsized
> length
> > of the upper beak to the mandible indicates a functional distinction
> to
> > some typical pterosaurs, which have relatively even lengths in these
> two
> > cranial segments. Moreover, the upturn can indicate "prying" behavior
> > (impairing fossil evidence of meals) -- much as has been suggested for
> > *Dsungaripterus weii* -- while the outsized upper to lower could
> > actually make the skull effectively a giant signaling device, and have
> > very little, if anything, to do with feeding.
> >
> > 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: Wed, 3 Nov 2010 10:07:12 +0000
> > > From: Mark.Witton@port.ac.uk
> > > To: dinosaur@usc.edu
> > > Subject: Re: How Pelicans learn to fish
> > >
> > > "Much has been written and speculated regarding pterosaur flying,
> but
> > > what about smacking the water?"
> > >
> > > Lots of folks have suggested Pteranodon may have plunged dive, with
> > > Chris Bennett most recently noting that the skeleton of Pteranodon
> is
> > no
> > > more fragile than that of Pelecanus and that diving from heights of
> 10
> > m
> > > or so was possible. However, the regurgitated gut content of
> > Pteranodon
> > > suggests that pretty dinky fish were being eaten, and Pteranodon has
> a
> > > particularly long, narrow skull that may be ill suited to grabbing
> > > mouthfuls of small fish in a pelican-like manner (indeed, you can
> > ignore
> > > the many claims that pterosaur and pelican bills are anything alike:
> > the
> > > little helical jaw joint of pterosaurs does allow for slight
> > expansion,
> > > but it's a million miles away from the multi-hinged, distensible
> > > mandibles of pelicans). I wonder if Pteranodon was feeding in a
> > slightly
> > > more careful manner, perhaps alighting on the water surface or
> > something
> > > like that.
> > >
> > > Mark
> > >
> > > Mike Habib 03/11/10 12:41 AM >>>
> > > No specific ones that I know of, but I haven't looked carefully. In
> > > both cases the skull is large and largely thinned-walled, but that
> > > probably isn't a diving correlate, per se. Maybe someone else here
> has
> > > looked at that in more detail.
> > >
> > > --Mike H.
> > >
> > >
> > > On Nov 2, 2010, at 7:47 PM, Dan Chure wrote:
> > >
> > > > Any structural convergences in the skull?
> > > >
> > > > Dan
> > > >
> > > > On 11/2/2010 5:21 PM, Mike Habib wrote:
> > > >> The only diving birds that fold back the wings in a "knife"
> > position
> > > are gannets and boobies (i.e. sulidae). Pelicans actually don't tuck
> > > their wings all that far back on dives; I doubt it's beyond the
> normal
> > > joint excursion for a modern bird.
> > > >>
> > > >> One bit of interest, though, is that the ratio of bone wall
> > thickness
> > > to total bone diameter in pelicans is very similar to that in
> derived
> > > pterodactyloids. It's about the same as Pteranodon, for example.
> > > >>
> > > >> Cheers,
> > > >>
> > > >> --Mike Habib
> > > >>
> > > >>
> > > >> On Nov 2, 2010, at 7:13 PM, Dan Chure wrote:
> > > >>
> > > --
> > >
> > > 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
> > >
> > > If pterosaurs are your thing, be sure to check out:
> > >
> > > - Pterosaur.Net: www.pterosaur.net
> > > - The Pterosaur.Net blog: http://pterosaur-net.blogspot.com/
> > > - My pterosaur artwork: www.flickr.com/photos/markwitton
> > > >>> Are there any osteological correlates to pelican diving
> behavior?
> > > One would be joints that allow the wings to be rotated backwards,
> but
> > do
> > > all diving birds do that or does diving occur in other ways in other
> > > birds?
> > > >>>
> > > >>> Dan
> > > >>>
> > > >>>
> > > >>> On 11/2/2010 2:05 PM, Richard W. Travsky wrote:
> > > >>>> Of course the first thing I thought of was pterosaurs...
> > > >>>>
> > > >>>> http://www.nytimes.com/2010/10/26/science/26qna.html
> > > >>>>
> > > >>>> Q. How do pelicans learn to dive for fish?
> > > >>>>
> > > >>>> A. Young pelicans learn to feed themselves through a
> combination
> > of
> > > trial and error, imitation of adult birds and instinct, bird experts
> > > suggest.
> > > >>>>
> > > >>>> In the United States, the Eastern brown pelican (Pelecanus
> > > occidentalis carolinensis) and the California brown pelican
> (Pelecanus
> > > occidentalis californicus) make dives onto schooling fish from
> > > impressive heights or float on the surface to scavenge fish. A dive
> > from
> > > 30 to 60 feet up, or even higher, hits the water with considerable
> > > force. Fish a few feet below the surface are scooped up, and water
> > > drains from the sides of the pouch. They tilt their heads back and
> > > swallow on the spot.
> > > >>>>
> > > >>>> For young pelicans, some early experience in diving for fish
> > comes
> > > during their time in the nest, when they graduate from feeding on
> > > half-digested fish bits regurgitated by their generous parents to
> > > retrieving fish from the famously capacious pouched parental bills
> and
> > > even their gullets. The nestlings may dive in shoulder deep to make
> > the
> > > parents disgorge fish. Pelicans are well fed in the nest for 9 to 11
> > > weeks, by which time they are fully feathered and ready to go out on
> > > their own.
> > > >>>>
> > > >>>> Their diving success rate is highly variable and depends on
> > > experience. Adult California brown pelicans bring up fish from
> around
> > > two-thirds of their dives, while novices appear to have a lot of
> > > trouble; fewer than half survive their first year out of the nest.
> > > >>>>
> > > >>>>
> > > >>>>
> > > >>>> Didn't know the mortality rate was that high.
> > > >>>>
> > > >>>> Much has been written and speculated regarding pterosaur
> flying,
> > > but
> > > >>>> what about smacking the water?
> > > >>>>
> > > >>>>
> > > >>>
> > > >> Michael Habib, M.S.
> > > >> PhD. Candidate
> > > >> Center for Functional Anatomy and Evolution
> > > >> Johns Hopkins School of Medicine
> > > >> 1830 E. Monument Street
> > > >> Baltimore, MD 21205
> > > >> (443) 280-0181
> > > >> habib@jhmi.edu
> > > >>
> > > >>
> > > >>
> > > >>
> > > >>
> > > >
> > > >
> > >
> > > Michael Habib, M.S.
> > > PhD. Candidate
> > > Center for Functional Anatomy and Evolution
> > > Johns Hopkins School of Medicine
> > > 1830 E. Monument Street
> > > Baltimore, MD 21205
> > > (443) 280-0181
> > > habib@jhmi.edu
> > >
> > >
> > >
> > >
> >
> >
>