Michael Habib | 1 Dec 08:51 2005

Re: large fossil birds


>>  Thus, I wouldn't expect overland flyers to always be selected for 
>> high wing loading
>
> Nor would I.  It depends upon the specific niche they are filling and 
> their usual source for atmospheric energy extraction.  Birds are more 
> versatile in that regard than pterosaurs were.  Birds exhibit 
> variations on more than one theme.  Pterosaurs exhibit variations upon 
> a single theme.  You've probably noticed that birds with low to 
> intermediate aspect ratios find tipslots advantageous while higher 
> aspect ratios shift to triangular wingtips. Pelicans are right on the 
> morphological dividing line between the two forms, and as far as I 
> recall, are the highest aspect ratio birds to make use of tipslots.  
> For birds with aspect ratios less than pelicans, there can be an 
> advantage to reducing wingloading.  For birds with larger aspect 
> ratios than pelicans, the advantage would usually seem to be toward 
> increasing it...

I am not aware of any birds with AR's higher than pelicans that utilize 
tipslots either.  In fact, a fair number of birds with AR's 
significantly lower than pelicans have tapered wingtips without slots 
(falcons, for example, though they are not exactly typical birds).  
There are also differences in how the wings are held across birds with 
different AR's.  For example, those with high aspect ratios tend to 
hold the tips of the wings angled slightly downward and back 
(especially by marine birds during rapid soaring).  If I remember 
correctly, this serves to form more favorable vortex patterns at the 
distal portions of the wing and thus reduce drag near the tips, but my 
memory may not be serving me correctly on that one.

(Continue reading)

Mike Taylor | 1 Dec 15:02 2005
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Looking for pre-2002 SVP Abstracts

Dear DMLers,

I often find the volumes of SVP abstract for the last four years
useful: they can be freely downloaded from the following URLs:

	http://www.vertpaleo.org/meetings/Abstracts02.pdf
	http://www.vertpaleo.org/meetings/VRPA2303supp_all.pdf
	http://www.vertpaleo.org/meetings/2004_SVP_abstracts.pdf
	http://www.vertpaleo.org/meetings/05_abstracts.pdf

(Note the total lack of pattern :-)

However, I've not managed to find a PDF for abstracts of meetings
earlier than 2002, and I wondered if anyone else has tracked them
down?  I've tried tweaking the URLs above for year-2001 --

	http://www.vertpaleo.org/meetings/Abstracts01.pdf
	http://www.vertpaleo.org/meetings/VRPA2103supp_all.pdf
	http://www.vertpaleo.org/meetings/2001_SVP_abstracts.pdf
	http://www.vertpaleo.org/meetings/01_abstracts.pdf

-- but they are all 404s.  This is a pain when I find that I need to
read a pre-2002 abstract such as:

	Holliday, C. M., Ridgely, R. C., Sedlmayr, J. C. & Witmer,
	L. M.  (2001). The articular cartilage of extant archosaur
	limb bones: implications for dinosaur functional morphology
	and allometry.  J. Vertebr. Paleontol. 21: 62A.

Thanks!
(Continue reading)

don ohmes | 1 Dec 15:12 2005
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Re: large fossil birds


--- Michael Habib <mhabib5 <at> jhmi.edu> wrote:

> 
> >>  Thus, I wouldn't expect overland flyers to
> always be selected for 
> >> high wing loading
> >
> > Nor would I.  It depends upon the specific niche
> they are filling and 
> > their usual source for atmospheric energy
> extraction.  Birds are more 
> > versatile in that regard than pterosaurs were. 
> Birds exhibit 
> > variations on more than one theme.  Pterosaurs
> exhibit variations upon 
> > a single theme.  You've probably noticed that
> birds with low to 
> > intermediate aspect ratios find tipslots
> advantageous while higher 
> > aspect ratios shift to triangular wingtips.
> Pelicans are right on the 
> > morphological dividing line between the two forms,
> and as far as I 
> > recall, are the highest aspect ratio birds to make
> use of tipslots.  
> > For birds with aspect ratios less than pelicans,
> there can be an 
> > advantage to reducing wingloading.  For birds with
> larger aspect 
(Continue reading)

jrc | 1 Dec 15:34 2005
Picon

Re: large fossil birds


----- Original Message ----- 
From: "Michael Habib" <mhabib5 <at> jhmi.edu>
To: "jrc" <jrccea <at> bellsouth.net>; <dinosaur <at> usc.edu>
Sent: Thursday, December 01, 2005 1:51 AM
Subject: Re: large fossil birds

>  For example, those with high aspect ratios tend to hold the tips of the 
> wings angled slightly downward and back

This is a multi-fold response, partly related to optimum orientation of the 
skeletal support system,  partly a response to the spanwise component of 
flow over the wing, and partly related to reducing span to minimize profile 
drag at the higher speeds associated with increased loading.

> (especially by marine birds during rapid soaring).

Reduction of span to reduce profile drag at high speed.  Note that falcons 
in a maximum dive will actually retract the wings so much that they form a 
double delta, with the tips brought in almost to the midline, and the 
effective tip being formed by the wrist.  Peregrines do this a lot.

>  If I remember correctly, this serves to form more favorable vortex 
> patterns at the distal portions of the wing and thus reduce drag near the 
> tips, but my memory may not be serving me correctly on that one.

This is correct for the mild aftward direction (it also greatly increases 
stability).  The extreme aftward position with retracted elbows and wrists 
forward tends to be associated with profile drag.  Also keep in mind that an 
elliptical planform doesn't result in minimum induced drag for a cranked 
(Continue reading)

jrc | 1 Dec 15:46 2005
Picon

Re: large fossil birds


----- Original Message ----- 
From: "don ohmes" <d_ohmes <at> yahoo.com>
To: <mhabib5 <at> jhmi.edu>
Cc: <dinosaur <at> usc.edu>
Sent: Thursday, December 01, 2005 8:12 AM
Subject: Re: large fossil birds

> +++++++++++++++++++++++++++++++++++++++++++++++++
>
> In wild type D. melanogaster (and drosophila
> generally), AR increases with size. Even a small
> sample of males ranging .5-.95mg will conform to this
> trend (p <.05), and given controlled conditions, AR
> increase can be consistently (75-80%) measured between
> flies with a weight differential of .1 mg! (Don Ohmes,
> unpublished data). In insects, the correlation seems
> to hold across taxa, _within wing (and presumably
> flight) styles_.

This is a Reynold's number effect.

>
> This implies that the optimal AR within flightstyles
> generally scales w/ size,

Agreed.

> and also that the AR at
> which tip slots become unfavorable in falcon-sized
(Continue reading)

don ohmes | 1 Dec 17:11 2005
Picon

Re: large fossil birds


--- jrc <jrccea <at> bellsouth.net> wrote:

> 
> ----- Original Message ----- 
> From: "don ohmes" <d_ohmes <at> yahoo.com>
> To: <mhabib5 <at> jhmi.edu>
> Cc: <dinosaur <at> usc.edu>
> Sent: Thursday, December 01, 2005 8:12 AM
> Subject: Re: large fossil birds
> 
> 
> > +++++++++++++++++++++++++++++++++++++++++++++++++
> >
> > In wild type D. melanogaster (and drosophila
> > generally), AR increases with size. Even a small
> > sample of males ranging .5-.95mg will conform to
> this
> > trend (p <.05), and given controlled conditions,
> AR
> > increase can be consistently (75-80%) measured
> between
> > flies with a weight differential of .1 mg! (Don
> Ohmes,
> > unpublished data). In insects, the correlation
> seems
> > to hold across taxa, _within wing (and presumably
> > flight) styles_.
> 
> This is a Reynold's number effect.
(Continue reading)

Michael Habib | 1 Dec 17:39 2005

Re: large fossil birds


On Thursday, December 1, 2005, at 11:11 AM, don ohmes wrote:

>>> Does anyone happen to know what the smallest bird
>> w/
>>> tip-slots is?
>>
>> Good question.  I don't know.
>
> Drat. Hoped you might know.

I don't know for sure either, but one good bet might be species in the 
bushtit group.  I know long-tailed tits have wing slots (albeit small 
ones; wing photograph at:  
http://www2.ups.edu/biology/museum/BUSHwing23359.jpg).  Long-tailed 
tits have extremely short, highly rounded wings and a very long tail 
(somewhat like accipiters but more extreme).   They weigh in somewhere 
around 8 grams, but some related species (which may also use slots) are 
as small as 6 grams.

Cheers,
--Mike

don ohmes | 1 Dec 18:06 2005
Picon

Re: large fossil birds

Very cool! What would be expected at the extreme end
of the scale.

One caveat which I just thought of; is tip-slot a
well-defined term, or is it like art and pornography?
I just realized I  don;t know...

Don

--- Michael Habib <mhabib5 <at> jhmi.edu> wrote:

> 
> On Thursday, December 1, 2005, at 11:11 AM, don
> ohmes wrote:
> 
> >>> Does anyone happen to know what the smallest
> bird
> >> w/
> >>> tip-slots is?
> >>
> >> Good question.  I don't know.
> >
> > Drat. Hoped you might know.
> 
> I don't know for sure either, but one good bet might
> be species in the 
> bushtit group.  I know long-tailed tits have wing
> slots (albeit small 
> ones; wing photograph at:  
>
(Continue reading)

Michael Habib | 1 Dec 18:09 2005

Re: large fossil birds

> This is a multi-fold response, partly related to optimum orientation 
> of the skeletal support system,  partly a response to the spanwise 
> component of flow over the wing, and partly related to reducing span 
> to minimize profile drag at the higher speeds associated with 
> increased loading.

Ah, okay, that all makes sense.

> Also keep in mind that an elliptical planform doesn't result in 
> minimum induced drag for a cranked wing.  Minimum induced drag for a 
> cranked wing occurs with a more triangular tip.

This doesn't surprise me, because it matches familiar biological 
patterns (ie. species using cranked wings generally have tapered tips). 
  Why is it, though, that cranked wings have a different optimal tip 
profile?

> Induced drag decreases with the square of the airspeed, so at high 
> speed the high effective aspect ratio is unnecessary and is reduced by 
> closing the tipslots (thereby also reducing the profile drag).  
> Essentially, they are morphing the wing for minimum total drag in 
> response to the speed that they wish to fly.

Interestingly, some eagles use very long, shallow stoops and will morph 
their wings gradually as they pick up speed to continually minimize 
drag (and probably also to increase wing loading to some degree).

> I would expect flight speed in the mid to large size azhdarchidae to 
> approach 45-70 mph with the larger ones being faster, but also note 
> that membrane wings have an upper speed limit that is a function of 
(Continue reading)

bh480 | 1 Dec 10:15 2005
Picon

News: Dino Lab Grant to Phil Currie

From: Ben Creisler bh480 <at> scn.org

In case this news item has not been mentioned yet:

http://www.gateway.ualberta.ca/view.php?aid=5331

Grant helps top dinosaur expert develop advanced 
palaeontology lab at U of A 

Derek Larson 

Even before Jurassic Park, dinosaurs had been the 
breadwinners of the palaeontological community, and one of 
this year’s Tier One Canadian Research Chairs is no 
exception. 

The federal government, through the Canadian Research 
Chair program, has given Dr Philip J Currie of the 
University of Alberta $1.4 million over seven years to 
study the prehistoric beasts. Currie, professor in the 
Biological Sciences Department as of October of this year 
and formerly of the Royal Tyrell Museum in Drumheller, 
couldn’t be happier. 

"I’m very pleased that I was able to capture one of these 
[Canadian Research Chairs], and the budgets that go with 
it," said Currie. "It’s a pretty good indication that the 
federal government ... is pretty serious about trying to 
keep scientists in Canada and to improve what’s being done 
in the country." 
(Continue reading)


Gmane