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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
>
>
>
>