Recovered: Tensegrity Structures in Biology

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nick c
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Re: Rigorous study of size limits for flying creatures

Unread post by nick c » Thu Oct 23, 2008 5:21 pm

substance wrote:I still cannot understand how EDM digging in the surface of the planet could leave exactly matching edges on both sides of the discharge affected area
Hello substance,
I am not sure if I understand your issue with EDM concerning matching edges. But it seems to me that EDM would produce one side matching the other. I can visualize a meandering arc discharge moving across a surface, carving out a (snake like, curving in and out) rille or rift where one side reciprocates the ins and outs of the opposite edge.

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Re: Rigorous study of size limits for flying creatures

Unread post by tholden » Fri Oct 24, 2008 7:58 pm

So I can't dismiss the possibility that dinosaurs came from Mars just yet....
The subject of what I'd call "splash saltations" appears to have come up spontaneously without me mentioning it.......

Granted this is an area of pure conjecture and wild guesses, nonetheless the following is more or less my version of it.

Both Wal Thornhill's vision and Al DeGrazia's vision of the antique system involve system wide atmospheres and planets approaching closely to one another; I see a possibility for animals to have ended up on the next planet at the time of one OR MORE of those events.

The fossil record of our planet indicates that new groups of animals have appeared suddenly at specific points in time. One possible explanation would be animals from the next planet landing in reasonably shallow areas of our seas and simply swimming ashore. There have been more than one of these saltation events; I'd assume that such events might have occurred more than once and that more than just the one other planet (Mars) might have been involved.

I'd guess that the older creations, possibly involving dinosaurs, might have been native to our planet and that the more recent groups, particularly mammals, might represent splash saltations. Granted midrashim and other literature describe dinosaurs walking around at a time just prior to the flood; they nonetheless describe them as oddities and in all likelihood leftovers; there probably weren't a whole lot of them left over at the time.

I'd also guess that hominids were either native here or represented an earlier saltation, and that modern man represented a later one if in fact that is how we got here.

The total lack of any evidence of cross-breeding between early modern humans and neanderthals was always a big mystery until they managed to analyze neanderthal DNA in the late 1990s. Neanderthal DNA turned out to be about halfway between ours and that of a chimpanzee and that ruled the neanderthal out altogether as any sort of an evolutionary antecedent to modern man. In order to be descended from something via any process resembling evolution, at some point, you need to be able to interbreed with the something and we could no more interbreed with neanderthals than we could with horses.

All other hominids however are further removed from us THAN the neanderthal; that leaves nothing on this planet which we could possibly be descended from. You have three viable choices:

1. Modern man was created from scratch here and recently.
2. Modern man was brought here from elsewhere in the cosmos ( including the possibility of a splash saltation).
3. Modern man was genetically re-engineered from hominid stock of some sort.

I've mentioned change in gravity as the major reason for the die-out of the larger dinosaurs; I don't have a theory as to why the smaller ones aren't still with us. Particularly the smaller carnosaurs would have represented an unacceptable threat to early humans; I see it as possible that our ancestors, possibly aided by the mammalian carnivores, deliberately exterminated all such.

Again we're talking pure conjecture here.... I see it as possible that this planet might have originally been conceived as some sort of an amusement park with large and dangerous animals running around and that at some later point, mammals were PUT here because it wasn't clear that anything else in the system would survive the approaching calamities. I'd also assume that the people who built those megaliths on Mars would have tried to get some of their people off to near stars since they could not have been totally certain that ANYTHING in this system would remain habitable. If nothing else, we should be sending probes off to Proxima Centauri as soon as we're capable of it to check for any signs of human habitation.


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Re: Rigorous study of size limits for flying creatures

Unread post by redeye » Fri Oct 24, 2008 10:45 pm

Both Wal Thornhill's vision and Al DeGrazia's vision of the antique system involve system wide atmospheres and planets approaching closely to one another; I see a possibility for animals to have ended up on the next planet at the time of one OR MORE of those events.
I might be way off here, but the bridging events you are talking would be analogous to the ion flux between Jupiter and Io. Nothing cohesive is crossing that bridge. You would be transported in/as a lightning bolt, I think.

The KT Extinction Event saw to 75% of living things on the Planet, From plankton to megafauna, and was almost certainly caused by a crash of the biosphere. The precursor for this may have been a change in the gravitational constant but you can't ignore the giant hole in the ground at Chicxulub or the millions of square miles of basalt lava left over from the Deccan Traps.

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Re: Rigorous study of size limits for flying creatures

Unread post by moses » Sat Oct 25, 2008 1:11 am

1. Modern man was created from scratch here and recently.
2. Modern man was brought here from elsewhere in the cosmos ( including the possibility of a splash saltation).
3. Modern man was genetically re-engineered from hominid stock of some sort.

Man has genes that were introduced into this planet. This strongly suggests to me
that we are a mixture of alien and local stock, and we thus do not know what we
are truly capable of.

I don't have a theory as to why the smaller ones aren't still with us. Particularly the smaller carnosaurs would have represented an unacceptable threat to early humans; I see it as possible that our ancestors, possibly aided by the mammalian carnivores, deliberately exterminated all such. Ted
I very much doubt that anything like us was around at or just after the extinction
event that wiped out the smaller dinosaurs. Possibly dinosaurs were wiped out on
Mars at the same time, or else transfer of material between planets ceased then.
But why some things survived is a mystery.

I might be way off here, but the bridging events you are talking would be analogous to the ion flux between Jupiter and Io. Nothing cohesive is crossing that bridge. You would be transported in/as a lightning bolt, I think.

I'm thinking much more electricity. So there would be a plasma cell around all the
planets with big electric currents moving around and through this cell creating an
atmosphere in this cell with pressure possibly of 1 atm. And when Mars neared
Earth things got wild and transfer of material occurred.

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Re: Rigorous study of size limits for flying creatures

Unread post by red44 » Sat Oct 25, 2008 8:48 am

Three cheers to Kevin. I think he might be on to something.
Or maybe the large "wings" were merely shelter for the creature's babies and juveniles.

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Re: Rigorous study of size limits for flying creatures

Unread post by kevin » Sat Oct 25, 2008 11:50 am

I had to look back to remember what I had said.
Basically, unless you are certain that all materials are reacting to the so called gravity the same, then I do not see how you can achieve any size limits relative to anything.
It is the ability of substances to interact with the two way wave fronts of sound ,that in my opinion cause the net push downward called gravity, and that those substances have refractive /reflective chirile capabilities that neutralise the normal dominant incoming wave front that is the cause of the effect we call gravity.
If at any point in time, those wave fronts have altered, then again the basic push may have been increased or decreased substantially, thus allowing rapid expansion in lifeforms, and any sudden increase in the net downward push , may explain extinctions as the life forms suddenly encountered a different rate of gravity., and were unable to adapt.
I doubt we have any method of knowing if the net gravity has suddenly altered?
But I assure you that I can detect the method that many substances and feathers utilise to alter the so called weight of those substances, and I intend to build a composite plywood type arrangement of such to hopefully alter the net push local to that ply arrangement.


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Re: Rigorous study of size limits for flying creatures

Unread post by SWAMP Yankee » Mon Oct 27, 2008 3:50 am

I have been a tpod lurker for quite awhile. I have to say, the presentation mr adams has put together re: expanding earth is very compelling. If one is dismissing out of hand without viewing the ( I wont say "evidence" but ) "reasonable inferences" well....

Not liking the theory because we don't know when why or how just doesn't stack up against some of the realities I think are quite clear. The first and best in my opinion is the [url2=]age of the ocean floor[/url2]. I would encourage a look or maybe a second look a [url2=]Neals videos on youtube[/url2] etc. Perhaps his idea re europa is off the mark i would suggest we just set that aside as a bogie and focus on his presentation of earth Mars and also [url2= ... 3127&hl=en]GANYMEDE[/url2].

Best Regards,


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Re: Rigorous study of size limits for flying creatures

Unread post by kevin » Mon Oct 27, 2008 7:57 am

Swamp Yankee,
If You when viewing your youtube link, try to consider a continuous expansion via implosion, where nothing actually moves, but the expansion matchs the movements of the imploding signal pathways.
Those imploding signals coalesce into matter, and the matter formed ebbs and flows similer to tidal waves, erroding one pathway and forming new on the other side.
That the universe is acting the same, a continuum of implosion into mass, not the other way around as per the big bang stuff.
The reason I say nothing actually moves, is that if you were to fix a point on the surface, and imagine that point having a pole shooting upwards at ninty degrees to it, then as the surface expands, the surface will creep up the pole, but the pole will still be the point, just further outwards in a diameter sense.
The expansion will then be a following of the turning of whatever drives the signals out in infinity, the resultant changes in diameter will lead to ever altering conditions upon the surface area, and that may not be a totally smooth alteration, but may be quite violent at specific timings, as the signals ebb and flow.
This is my opinion, and is one of the reasons I think the earth and everything else is stationary, and that all we mistakenly percieve is via the movements of the aether substance via the signal pathways that creates, but this is the new insights and mad ideas area?

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Re: Rigorous study of size limits for flying creatures

Unread post by Grey Cloud » Mon Oct 27, 2008 8:27 am

Hi Kevin,
You wrote
This is my opinion, and is one of the reasons I think the earth and everything else is stationary, and that all we mistakenly percieve is via the movements of the aether substance via the signal pathways that creates, but this is the new insights and mad ideas area?
This is not only your opinion and it is a very old insight. The Ptolemic geo-centric model was not originally a model of the physical solar system but of the metaphysical. Nietzsche also didn't have much time for anyone who thought the Earth revolved around the Sun.
If I have the least bit of knowledge
I will follow the great Way alone
and fear nothing but being sidetracked.
The great Way is simple
but people delight in complexity.
Tao Te Ching, 53.

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Re: Rigorous study of size limits for flying creatures

Unread post by kevin » Mon Oct 27, 2008 10:24 am

Grey cloud,
To stear the thread back onto track, I should better explain.
As in that youtube link, it is assumed (ass-u-me)that the earth is floating along in space, and that pathway is controlled by gravity.
And it is that force gravity, that will determine the ability of anything to fly.
But I do not consider there is any force called gravity, so what is involved?
Why do we observe the moon going around the planet, never mind the sun, the moons the nearest, and I consider the biggest clue.
It almost defies logic to propose that the moon is not moving, but I am.
There is movement involved, but not as we percieve of it, it is instead the movement, and in the moons case this involves the circulating flow of the aether around the earth, in the earths case it is the circulating flow around the sun, and there are numerous circulations involved at different diameters, and thats where the eyes are decieved.
they and anything built here to enchance them, are decieved by the method of signal distribution and return, it is not linear based, but is warped around the circulations, and the result is a false picture of movement, with all the measure almost matching the accepted linear concept.
Back to gravity, which I consider is an electrical consequence of the above situation, where an implosion into the formed planet is occuring down spiral vortex pathways that are created most bizzarely by dead straight lines, but they are arranged in such fashion as to produce spiral shapes of descending and ascending scale pathways.

That anything desiring to overcome the dominant inward push of this system needs to be able to deflect the imploding aether and redirect it in as much the opposite direction as possible in a local field arrangement created about the object desiring to be pushed away from the planets surface, or in whatever direction that object directs the local field into.

Because I can detect what a feather does, I can percieve of how this is achieved, not a full push away, or you would dissappear off out into the space, but a partial field alteration, with the atmosphere also employed for flight.

If you can imagine the attraction in zillions of spiral pathways, and them all been to a scale of geometric brilliance that leads to higher concentration points on a geometric planet, but that the circulation flows smooth out all of the geometrically formed points into a near sphere, but with a predominant area around the equator, due to the predominant circulations of aether centred around that area( think saturn)
With a torroidal dual circulation pattern giving the poles, and them been somewhat flattened as a result.
If You can percieve of this, then you can see yourself, as we are a consequence to scale of this whole system.
But we adhere to the dominant system, and thus are pushed to the surface, but with push in all directions as well , hence we can move and have form, otherwise we would be flat at the surface.
The trick, quite simply is to turn around the field pattern about ourselves, then levitate, we do not have the required abilities to do this , but some things such as birds do, all my humble opinion.


Re: Rigorous study of size limits for flying creatures

Unread post by lizzie » Wed Oct 29, 2008 5:35 am

Kevin said: There is movement involved, but not as we percieve of it, it is instead the movement, and in the moons case this involves the circulating flow of the aether around the earth, in the earths case it is the circulating flow around the sun, and there are numerous circulations involved at different diameters, and thats where the eyes are decieved.
Kevin, I think I finally understand what you are sayinig. The waves (ether) produce the energy “flow” but only they move; the particles do not even though at first glance they appear to do so. ... otion.html

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Re: Rigorous study of size limits for flying creatures

Unread post by kevin » Wed Oct 29, 2008 7:51 am

If you read what Walter russell proposed, then it becomes even clearer, as much as it can be.
Each point( centre of planet etc) is a position in a vast sea of geometry, and each such point has to scale exactly that which is detectable upon the surface in 2D.Remember I am simply slicing through a section just above the surface.
Each point is a centre point of spiral pathways, so in a spheres case this is pathways from millions of such, but they are all to scale of ever larger and larger and larger same spirals.
Around each point are circulations that are both circulating and contributing into the spiral inward pathway.
Anything within one of these circulations ( our planet around the sun, the moon around the earth, the sun around the galatic centre) will encounter alignments of less resistance that leads down into the next smaller circulation, hence everything is heading into a spiral centre point.
Bizzarely at the self same time the exact opposite is occuring, and everything is also heading outwards to the edges, confusing it sure is?
At every level of scale, a dominant cross feature occurs due to the fibonacci geometry involved, around any circulation I detect, there is a maximum of 55 lines around 180 degrees, so 110 around 360 degrees, but four of those will have many lines close to them, so a dominance in flow effects occurs.

This all has a bearing on this thread, because at measurable time , I consider that the planet will encounter these 110 input lines as it completes its 26,000 year trundle about the so called zodiac, and I think it is the aether moving in this way giving the illusion of the planet moving, but also leading to different levels of input and output from the planet which in turn will give different gravity conditions, if we simply look at fossils and ASSUME a self same condition existing through time, we will be fooled.
To even further complicate everything is that I consider the whole thing is alive, and as it moves different levels of information become available at these junctions , thus life forms morph and operate differently dependent upon this information, thus life forms may suddenly know and have available information to counter what we percieve of as gravity, and dependant upon what that lifeform is will lead to it adapting in infinite variety of ways, phew?

We are been super arrogant to ASSUME anything about a system we KNOW so little of.
Thanks for your wonderfull efforts to better comprehend , what is so blooming confusing.
I cannot with evidence explain all I KNOW, it hit me in a flash, so if walter Russell got 39 days worth, wow, he must have had the capacity open to store and recieve it.
Never, ever forget that it is alive, and We are it, it is us, the way it is misstreated at the moment is diabolical, and it is to ourselves we are doing it, just as killing any living thing is killing yourself, we need not blame ourselves as we did not know, so we will be forgiven, but once we KNOW, then the responsibility changes, I KNOW.

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flying creatures do fly 1

Unread post by StefanR » Thu Oct 30, 2008 8:29 am

So is there nothing to say about the flying creatures anymore? Or is there something the largest of pterosaurs have in common with other large animals in the past? A property of somesort that equally explains why mammals or birds have not reached such 'sizes'? Or a property that made them proficient and maybe flyers?
It seems logical to look at what made a pterosaur fly and for that it seems looking at the form, structure and behaviour of the animal. But as it pertains to an extinct animal of which no living relatives are present studying it's behaviour can only be done again from studying the function of the form and structure of the remains and making careful comparisons to living non-related animals with a similar form and structure. We must be careful as we are comparing similarities in different organisms, so we should also keep the differences in mind and not forget that the organisms are different. It's about the function of the structures displayed by the organism and their ability to perform a certain action that is the crux of the matter.
My humble apologies for the lenght of it all, but as this quite a comprehensive subject it's the only way for me to give my point of view. I have tried to give as many sources as I could that might give a certain consideration of what life is able of doing.

Structure, form, and function of flight in engineering and the living world
By combining appearance and behavior in animals with physical laws, we can get an understanding of the adaptation and evolution of various structures and forms. Comparisons can be made between animal bodies and various technical constructions. Technical science and theory during the latest decades have resulted in considerable insight into biological adaptations, but studies on structures, forms, organs, systems, and processes in the living world, used in the right way, have also aided the engineer in finding wider and better solutions to various problems, among them in the design of micro-air vehicles (MAVs). In this review, I discuss the basis for flight and give some examples of where flight engineering and nature have evolved similar solutions. In most cases technology has produced more advanced structures, but sometimes animals are superior. I include how different animals have solved the problem of producing lift, how animal wings meet the requirements of strength and rigidity, how wing forms are adapted to various flight modes, and how flight kinematics are related to flight behavior and speed. ... 1&SRETRY=0
Animal Locomotion
Animal locomotion is the study of how animals move.
Not all animals move, but locomotive ability is
widespread throughout the animal kingdom.
As all animals are heterotrophs, they must obtain food
from their environment.
Some animals such as sponges are sessile, and move
the fluid in which they live through their body (this is
known as filter feeding).
However, most animals must move around to find food,
a mate, and so forth. Ability to do so efficiently is
therefore essential to their survival.
Flight has independently evolved at least 4 times in the
birds, and
Gravity is a major problem for flight through the air.
Because it is impossible for any organism to approach the
density of air, flying animals must generate enough lift to
ascend and remain airborne.
Wing shape is crucial in achieving this, generating a
pressure gradient that results in an upward force on the
animal' body.
The same principle applies to airplanes, the wings of which
are also airfoils.
Other structural modifications of flying animals include
reduced and redistributed body weight,
fusiform shape, and
powerful flight muscles
Flight Forms
Falling / Diving: Decreasing altitude under the force of
gravity, using no adaptions to increase drag or provide lift.
Parachuting: Defined as falling at greater than 45 degrees
from the horizontal with adaptations to increase drag
forces. Very small animals may be carried up by the wind.
Gliding: Defined as falling at less than 45 degrees from the
horizontal. Lift caused by some kind of aerofoil mechanism,
allowing slowly falling directed horizontal movement.
Streamlined to decrease drag forces to aid aerofoil. Often
some maneuverability in air.
Soaring: Appears similar to gliding but is actually very
different, requiring specific physiological and morphological
adaptations. The animal keeps aloft on rising warm air
(thermals) without flapping its wings. Only large animals
can be efficient soarers.
Flapping: Flapping of wings to produce thrust. May ascend
without the aid of the wind, as opposed to gliders and
Note: These forms of aerial locomotion are not mutually exclusive and indeed many animals will
employ two or more of the methods.
Wing shape and flight
The shape of the wing is an important factor in
determining the types of flight of which the bird is
Different shapes correspond to different trade-offs
between beneficial characteristics, such as speed,
low energy use, and maneuverability.
The platform of the wing can be described in terms of
two parameters:
aspect ratio: the ratio of wingspan to the mean of its
wing loading: the ratio of weight to wing area.
Most kinds of bird wing can be grouped into four
types (with some falling between two of these types)
elliptical wings,
high speed wings,
high aspect ratio wings and
soaring wings with slots. ... motion.pdf

Power-to-Mass, Morphing, and How Birds Use Half a Wing

Most birds possess an array of locomotor features that permit extraordinary maneuverability, rapid acceleration and deceleration, and efficient long-distance travel. This broad range of flight capabilities should be as inspiring to aeronautical engineers and pilots today as it was for the first innovators of human flight. In fact, issues related to form and function continue to be of interest to both biologists and aeronautical engineers whose focus is to elucidate underlying principles of flight performance.

In this paper, I briefly discuss recent research advances in: (1) measuring power-to-mass ratios and its influence on animal behavior, (2) how birds dynamically change shape or “morph” in flight, and (3) how some birds employ wing-assisted incline running (WAIR) and turn their wings into negative thrust generating devices. This last section relates to the novel use of flapping proto-wings and addresses the evolution of flight in birds. Arguably, all of these issues have potential applications to future aviation and robotic technology.

How an animal exploits its three-dimensional environment is largely based on the relationship between its mass, the properties of its locomotor machinery (e.g. muscle
investment and fiber types), and the density of the medium in which they travel.

Our hypothesis poses that differences in morphology, wing kinematics, overall style of flight, and potential morphing ability have major effects upon the magnitude and shape of a species’ power curve.

Continued technological advances in biomechanical and motion recording equipment (e.g., high-speed light and x-ray digital video, animation software, and miniature bioelectrical devices) is permitting unprecedented visualization and quantification of the internal and external structures of moving animals. Future studies in flight behavior, physiology, and mechanics will provide novel and functional models for aeronautical engineers involved in developing future aircraft (e.g., micro-air vehicles, general and military aircraft). ... .final.pdf
Starting in 1984, the team developed a large radio-controlled, wing-flapping, flying replica of the largest animal that ever flew: the long-extinct pterodactyl Quetzalcoatlus northropi, whose giant wings spanned 36 feet. This QN replica became the lead "actor" in a 1986 wide-screen IMAX film titled "On the Wing", a film depicting the interrelation between the developments of biological flight and aircraft. Johnson Wax and the National Air and Space Museum sponsored the film and the QN replica

A hang glider is an unpowered ultralight aircraft that is capable of being foot launched and is controlled via pilot weight shift and/or the actuation of aerodynamic control surfaces. The definition of 'hang glider' per the international hang gliding commission, or Commission Internationale de Vol Libre (CIVL), which operates under the auspices of the Federation Aeronautique Internationale (FAI), is:

A glider capable of being carried, foot launched, and landed solely by
the use of the pilot's legs.

There are four distinct classes of aircraft which are covered by the definition of 'hang glider':

* Class 1 - Hang gliders having a rigid primary structure and controlled by weight shift only and which demonstrate consistent ability to safely take-off and land in nil wind conditions.
* Class 2 - Hang gliders having a rigid primary structure and controlled by deflection of aerodynamic control surfaces as the primary method of control in at least one major axis and which demonstrate consistent ability to safely take-off and land in nil wind conditions.
* Class 3 - Hang gliders having no rigid primary structure and which demonstrate consistent ability to safely take-off and land in nil wind conditions.
* Class 4 - Hang gliders which are unable demonstrate consistent ability to safely take-off and land in nil wind conditions but that otherwise are capable of being launched and landed by the use of the pilot's legs.

The wing of a hang glider generates lift when air flows across it from fore to aft, like any airfoil. The amount of lift produced is not enough to overcome the force of gravity (climb), but is enough to slow the descent rate in still air to about 200 feet per minute (FPM). If the glider flies in air rising at more than the glider's sink rate then the glider will gain altitude, or soar. The stall speed of a hang glider is 18-22 mph, best glide is usually just under 30 mph, and top speeds are around 60 mph, though speeds of 80-100 mph can be achieved during aerobatic maneuvers. At best glide speeds hang gliders have glide angles of between 9:1 and 14:1. Sink rates vary from about 200 fpm just above stall speed (minimum sink) to as much as 1500 fpm for low performance wings at top speed. Sink rate increases more or less linearly with airspeed and is the main topic when hang glider performance is discussed. Most flying is done in the narrow range between minimum sink, when climbing in lift, and best glide, when going from point to point. Airfoil profile, aspect ratio and percentage of double surface determine to a great extent the performance of a wing. Thick-cambered low aspect (5. 5) wings with little or no double surface are slow and docile, usually with great low-speed characteristics. Wide (>7. 5 AR), skinny 'blade wings' with 80% or more double surface are made for racing and require finesse to realize their potential.

A given wing planform's useful load capacity is a function of its area. Glider models come in several sizes to cover the range of pilot sizes, and gliders are referred to by model and size, either in square feet or square meters. The smallest racing gliders, for 100 lb. pilots, are about 120 square feet, while 225 - 250 square foot gliders have been made for tandem (two-person) operation. A 190 lb. pilot might fly a 195 square foot beginner glider or a 150 square foot high performance model. Wing loading determines sink rate and control authority. The example pilot just mentioned would have a wing loading of about 1. 3, including harness, helmet, parachute, instruments, and glider weight. At higher wing loadings a glider will fly, but will have an increased sink rate, and will also be more responsive to control inputs. Conversely, a lightly loaded glider will have a better sink rate but will take longer to respond to control inputs. Thus, a pilot can choose a model and size of glider suited to the type of flying desired. ... raptor.jpg
Wing area (m²) : 15.04
Wing span(m) : 12.49
Aspect ratio : 10.5
Hang glider weight (kg) : 34
Minimum pilot weight (kg) : 59
Maximum pilot weight (kg) : 112 ... raptor.htm
The illusion from which we are seeking to extricate ourselves is not that constituted by the realm of space and time, but that which comes from failing to know that realm from the standpoint of a higher vision. -L.H.

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flying creatures do fly 2

Unread post by StefanR » Thu Oct 30, 2008 8:36 am

This is just a quick survey of *what* soft tissues are known or can be directly inferred in pterosaurs based on a variety of specimens. I won’t be going into the details of which specimens preserve which bits, how, where you can see them, what they mean or how they function – that would take pages and pages. This is meant just as a quick overview to show what can be gleaned from the fossils and it is far more than you might think (pterosaur courtesy of Dino Frey). While of course we can infer that as vertebrates pterosaurs had eyes, hearts, lungs, livers, kidneys, skin, and muscles these are rarely if ever recorded in the fossil record at all, and of course the fragmentary nature of the pterosaur fossil record (compared to say, dinosaurs) means that these events should be far rarer. However the ‘damage’ is offset by the fact that a great many pterosaurs come from lagerstaaten deposits of exceptional quality, and thus a great many features are preserved on occasion
http://archosaurmusings.files.wordpress ... =500&h=295
Sadly there is no direct evidence of the air sac system, but the pneumatic nature of the bones and the pneumatopores that lead to them are a clear indication that they existed with Rhamphorhynchus being a good example. ... t-tissues/

Note the small size of the Pteranodon's body compared to the length of the head, and to the wings. Pteranodons were superbly adapted to flight, including their hollow, pneumatic bones and the way in which their dorsal vertebrae were fused together with the ribs to form a solid structure (notarium) that supported the flight muscles. While they were excellent long distance flyers, they probably spent more time soaring than flapping their wings.
Hatzegopteryx apparently had a robust skull broadened in the rear, and a massive jaw. Its lower jaw featured a unique groove in its point of articulation, also seen in some other pterosaurs, that would have allowed the animal to achieve a very wide gape. Many of the fossilized bones of Hatzegopteryx closely resemble those of the closely related Quetzalcoatlus, though in Hatzegopteryx the skull was much more heavily built, and had a markedly different jaw articulation similar to that seen in Pteranodon.

The skull of Hatzegopteryx was also unique in its heavy, robust construction. Most pterosaur skulls are made up of very lightweight plates and struts. In Hatzegopteryx, the skull bones are stout and robust, with large-ridged muscle insertion areas. In their 2002 description, Buffetaut and colleagues suggested that in order to fly, the skull weight of this pterosaur must have been reduced in some unconventional way (while they allowed that it could have been flightless, they found this unlikely due to the similarity of its wing bones to flying pterosaurs). The authors theorized that the necessary weight reduction was accomplished by the internal structure of the skull bones, which were full of small pits and hollows (alveoli) up to 10mm long, separated by a matrix of incredibly thin bony struts (trabeculae), a feature also found in some parts of Hatzegopteryx wing bones. The authors pointed out that this unusual construction, which differed significantly from the irregular internal structure of other pterosaur skulls, resembles the structure of expanded polystyrene, the substance used to make Styrofoam. They noted that this would allow a sturdy, stress-resistant construction while remaining lightweight, and would have allowed the huge-headed animal to fly.

Postcranial pneumaticity in pterosaurs: perspectives on pulmonary structure and the evolution
of body size
1Patrick O’Conner, 2Leon Claessens & 3David M. Unwin
1Ohio University, USA. 2College of the Holy Cross, USA. 3University of Leicester, UK.
Pterosaurs represent one clade of extinct archosauriforms for which pneumaticity of the
postcranial skeleton has been inferred based on morphological comparisons with extant birds.
Postcranial skeletal pneumaticity in living birds is derived from an extensive pulmonary air sac system, diverticula of which invade components of the postcranium, thus resulting in an air-filled skeleton. The skeletal manifestation(s) of pneumaticity, pneumatic foramina and/or fossae in communication with large internal bony cavities, are characteristic osteological correlates related to the presence of a heterogeneously-partitioned (i.e. one with distinct exchange and non-exchange regions) pulmonary apparatus. An air-filled skeleton in a flying animal no doubt serves a variety of functions, perhaps none as important as allowing a disproportionate increase in volume without the typical mass increase observed in the majority of terrestrial vertebrates.
Pneumatic features in individual bones of pterosaurs form the basis for numerous inferences,
including (1) the identification of the presence of a heterogeneously-partitioned pulmonary system and (2) hypotheses regarding specific components (e.g., individual diverticula) of the pulmonary apparatus.
For example, pneumatic foramina on the lateral surface of cervical vertebral centra in certain
pterosaurs (e.g., Anhanguera) indicate the presence of lateral vertebral diverticula in the neck, likely originating from a cranial section of the pulmonary system. Patterns of whole-body pneumaticity can provide important phylogenetic data and are perhaps related to ecological specializations and/or body size evolution within different groups. For example, it is only in the largest pterosaurs (e.g., certain pterodactyloids) that distal forelimb elements such as
syncarpals and phalanges are pneumatized. A similar pattern of distal forelimb pneumaticity and very large body size is also observed in some clades of living birds (e.g., pelicans, vultures, bustards), underscoring a possible functional linkage between body size evolution and the ability to pneumatize the postcranial skeleton, thereby decoupling typical volume—mass relationships. We hypothesize that the ability to pneumatize the postcranium via a pulmonary air sac system underlies the rapid body size diversification apparent in the Upper Jurassic/Cretaceous radiation of pterodactyloids generally, and was critical in the evolution of extremely large size (> 5 m wingspan) in several ornithocheiroids and azhdarchoids
Pterosaur heavyweights: a new approach to investigating pterosaur mass and its implications
for pterosaur flight O
Mark Witton
University of Portsmouth, UK.
Determining pterosaur mass is a problematic exercise, with its uncertainty well demonstrated
by the range of mass estimates accredited to certain taxa. The greatest problem with traditional
techniques is determining pterosaur body density: pterosaurs possessed pneumatised skeletons but their soft-tissue pneumaticity is unknown, making mass estimates reliant on this quantity questionable.
An alternative method that sidesteps this issue by focusing wholly on osteological data is presented here. Relationships between skeletal mass and body mass in extant birds and mammals are almost identical across both groups despite disparate phylogeny, anatomy and ecology (Prange et al. 1979), and this relationship has been exploited here to calculate pterosaur mass through geometric models of pterosaur skeletons. Skeletal pneumaticity was modelled using regression analysis of bone diameter to bone wall thickness with data from Bramwell and Whitfield (1974) and Steel (2004). Masses of 19 pterosaurs were estimated, representing the breadth of pterosaur phylogeny and size. Resulting mass estimates were three times greater than most previously published figures for equivalently sized pterosaurs (e.g. Hazlehurst & Rayner 1992), with the smallest (Anurognathus, wingspan 0.37 m) reaching 0.039 kg and the largest (Quetzalcoatlus, wingspan 9.91 m) at 235 kg. In order to asses the implications of higher mass estimates on pterosaur flight, wing areas were measured for modelled taxa to calculate wing loading and aspect ratios. An ankle-attachment was assumed for the cheiropatagium based on recent fossil evidence showing broad wing shapes throughout numerous pterosaur clades (e.g Frey et al. 2003). Principal component analysis was used to compare pterosaur wing data with previous models and modern volant forms (see Hazlehurst and Rayner 1992). Contrary to previous studies, pterosaur wing loading was not found to be lower than that of birds or bats. The increased extendibility of the pterodactyloid metacarpal results in a distinction between short, broad wings in non-pterodactyloids and narrow, tapered wings in pterodactyloids. The most derived wing shapes correlate with other derived aspects of pterosaur anatomy and may reflect increased ecological specialisation in these forms. Dimorphodon wing ecomorphology suggests it was a relatively reluctant flier, while Anurognathus has wing attributes similar to those of modern hirundines. Large size generally correlates with static soaring (e.g. azhdarchids, Huanhepterus) or dynamic soaring (ornithocheiroids). ... Munich.pdf
Wing structure and flight capability.

Research into pterosaur flight has principally focused on ornithocheiroids like Pteranodon [15], [66]–[69] and Anhanguera [70], with some studies investigating multiple pterosaur taxa [16], [71], [72]. Azhdarchid flight has yet to be researched in great detail and some controversy surrounds their flight capability. Paul [73] and Frey et al. [74] concluded that azhdarchids would be able to perform prolonged flapping flight using large flight muscles, with Paul [73] suggesting this for even the largest forms. Other workers have argued that the flight muscles of large pterosaurs were not sufficient to maintain flapping flight [16]–[18], [75] and that they were dynamic soarers akin to modern albatrosses [16], [18]. Similar conclusions were drawn by Lawson [2], but vulture-like static soaring was suggested rather than dynamic soaring.

Drawing conclusions about the flight of pterosaurs is problematic due to our limited understanding of their paleobiology. Modelling flight is particularly difficult for the larger forms due to the lack of equivalently sized extant analogues [72]: the absence of such creates problems in estimating the masses of giant pterosaurs, a critical value in modelling even basic flight attributes such as wing loading and flight speed. Despite many attempts at estimating the masses of giant azhdarchids, little agreement has been achieved.

Considerably higher estimates are given by Marden [79] and Paul [73] at 200–250 kg, but calculations by Chatterjee and Templin [16] suggest a pterosaur of this magnitude would never become airborne. These calculations are contradicted by Marden [79], and other workers have criticised lower mass estimates for being impossibly low [66], [73], [80].

It is noteworthy that all mass estimates of azhdarchids have been based on methods for which pterosaur soft tissue density has to be estimated. Many pterosaurs exhibited extensive skeletal pneumaticity (e.g. [31], [81]) and azhdarchid vertebrae and humeri were clearly pneumatised [29], [40]. We therefore assume that azhdarchids exhibited pneumaticity in both their soft tissue anatomy as well as in their skeleton. However, given that pneumaticity has been shown to vary considerably among extant birds [82] and has a significant impact on mass estimates [83], we know too little about pterosaur anatomy to accurately predict their masses using density-dependent calculating techniques.

With the relatively low wing loading that such broad wings produce, it is likely that large azhdarchids were also static soarers, using the warmed, rising air of thermals to gain altitude before soaring cross-country. Smaller azhdarchids may have been more capable of complementing gliding with sustained flapping flight than larger forms due to their lower masses and less demanding energetic requirements [16], [72]. These observations are supported by principal component analysis of azhdarchid wing form, with 10 m and 3 m span taxa plotting in the same ecomorphospace as condors, ibises and other thermal soarers [see 85 for further details]. The shape of azhdarchid wings implies that, like modern static soarers, they would have had relatively small turning radii when soaring, but comparatively poor glide performance compared to longer, narrower-winged forms [85], [92]. However, their broad wing area would act in concert with the deep camber produced by the elongate pteroid [40] to generate greater lift than that present in the narrower wing planform of dynamic soarers [70], [92]. This may have been crucial for azhdarchids, allowing them to take off in cluttered inland habitats where wind and topography are too variable to always allow an assisted takeoff. Additionally, it is of obvious benefit to have short, broad wings when taking off in vegetated inland settings [85]. That azhdarchids appear to have wings well adapted for flight in terrestrial environments correlates well with the regular occurrence of azhdarchid fossils in terrestrial strata.

The azhdarchid skull has a similar construction to modern birds that habitually stalk terrestrial environments (such as marabou storks and ground hornbills; Figure 7D) in bearing a long but relatively deep rostrum that extends anteriorly without invasion of the nasoantorbital fenestra (as is typical of other azhdarchoids [e.g. 11], [12]).

Hence, although azhdarchid anatomy is unique in a number of aspects, they appear to have been stork- or ground hornbill-like terrestrial stalkers (Figure 9), with the best modern analogues being the most generalized storks, such as the Ciconia species.

Concluding remarks

Studies of pterosaur ecology have suffered from the dogmatic attitude that pterosaurs were predominately aerial piscivores living in coastal settings, in spite of steady accretion of evidence that they occupied a variety of ecological roles in a suite of environments. The unusual anatomy of azhdarchids strongly indicates that they had a unique ecology and inhabited unusual environments compared to many other pterosaurs: these details have been overlooked by most authors who have interpreted azhdarchids as marine piscivores occupying niches conventionally considered typical of pterosaurs as a whole. This unusual lifestyle may explain the resilience of azhdarchids to decline in contrast to other Cretaceous pterosaur lineages, few or none of which persisted to the late Maastrichtian as did azhdarchids. It is hoped that this re-revaluation of azhdarchid ecology will inspire much-needed descriptions of azhdarchid material, empirical testing of the hypotheses presented here, and further research into the lifestyles of pterosaurs beyond their flight capability. ... ne.0002271
The Lungs and Air Sacs 3
Like birds, pterosaur's lungs were attached to an extensive series of air sacs. The air sacs had several functions, firstly to act as "bellows" for the lungs. This allows the air to flow through the lungs in only one direction, which is a more effecient system to our bi-direction lungs. Secondly, they were used to invade the bones - essentially fill them with air - which meant the bones could be bigger, without being any heavier. Thirdly, the air sacs may have have played a structural role in holding wing shape and posture, as they to in some birds.
This is a multi-layered diagram of the main structural elements of a pterosaur, based on Anhanguera (including A. piscator and A. santanae). Much of it is highly speculative, as obviously, not much of the soft tissue is preserved in the fossil record. There are many clues, however, such as fossil impresssions of skin, some muscle1, muscle scars on the bones, and pneumatic foramina (holes and depressions in the bones) for air sacs.
Four attributes of pneumatic bones are listed above under “Description of Pneumatic Elements”:
(1) external pneumatic features, (2) internal structure, (3) ASP, and (4) distribution of pneumaticity in the skeleton. Only the second attribute has been systematically surveyed in sauropods (Wedel 2003b), although aspects of the first are treated by Wilson (1999). Knowledge of the fourth is mainly limited to the observation that diplodocines and saltasaurines have pneumatic caudal vertebrae and other sauropods do not (Wedel 2003b). All existing data on the ASPs of sauropod vertebrae are presented in table 7.2. Not only do all four attributes need further study, but the levels of serial, ontogenetic, and intraspecific variation should be assessed whenever possible. Similar data on PSP in pterosaurs, nonavian theropods, and birds are needed to test phylogenetic and functional hypotheses. The pneumatic diverticula of birds are morphologically and morphogenetically intermediate between the core respiratory system of lungs and air sacs and the pneumatic bones. Understanding the development, evolution, and possible functions of diverticula is therefore crucial for interpreting patterns of PSP in fossil vertebrates.

The best evidence for pneumaticity in a fossil element is the presence of large foramina that lead to internal chambers. Based on this criterion, pneumatic diverticula were present in the vertebrae of most sauropods and in the ribs of some. Vertebral laminae and fossae were clearly associated with pneumatic diverticula in most eusauropods, but it is not clear whether this was the case in more basal forms. Measurements of vertebral cross sections indicate that, on average,
pneumatic sauropod vertebrae were 50%–60% air, by volume. Taking skeletal pneumaticity
into account may reduce mass estimates of sauropods by up to 10%. Although the functional and physiological implications of pneumaticity in sauropods and other archosaurs remain largely unexplored, most of the outstanding problems appear tractable, and there is great potential for progress in future studies of pneumaticity. ... d-figs.pdf
The illusion from which we are seeking to extricate ourselves is not that constituted by the realm of space and time, but that which comes from failing to know that realm from the standpoint of a higher vision. -L.H.

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Re: Rigorous study of size limits for flying creatures

Unread post by StefanR » Thu Oct 30, 2008 8:44 am

We aim to understand the flight mechanics and dynamics of pterosaurs, and related aspects of functional morphology, biomechanics and flight evolution. Pterosaurs evolved from small, stable flyers in the Triassic and Jurassic to become very large and very agile flyers in the Late Cretaceous. These highly derived pterodactyloids exploited their flexible membrane wing structure for flight control and propulsion.

The main questions we will address in this study are:
• How did large derived pterosaurs exploit aeroelasticity for control and propulsion?
• What are the probable bone, muscle and membrane properties related to flight?
• What muscle actuations and energy expenditures were needed to sustain flight?

A major strength in this work is the integration of functional morphology, evolutionary paleontology, flight mechanics, and biomechanics.
Late Cretaceous pterodactyloid pterosaurs were primarily large animals (wingspan 2-11 meters) that flew in very different ways from more basal pterosaurs. The “rhamphorhynchoid” pterosaurs of the Jurassic had long tails, which conferred dynamic stability while permitting a substantial degree of maneuverability (Wellnhofer, 1991; Witmer et al., 2003). The derived pterodactyloids, which were originally relatively small (wingspan <1 meter) lost the tail and reconfigured the wing, which permitted even better maneuverability. The more basal “rhamphorhynchoids” died out not long thereafter, and the Cretaceous history of pterodactyloids is principally a series of trends toward larger size, more soaring mechanics, and the iterated evolution of large and often bizarre cranial crests. A principal focus of this study is the functional morphology of the skeletal elements most involved in the generation of thrust and lift and the control of the wing.

One principal question in pterosaur biology is the shape, extent, and attachment of the wing membranes (Padian and Rayner 1993, Unwin 1999, Bennett 2000). Did they extend as far posterior as the hip, the thigh, or the ankle? Regardless of posterior extent, was the trailing edge straight or curved? Although a trailing edge tendon was apparently not necessary for flight control (Padian and Rayner 1993), evidence of it has now been adduced (Tischlinger and Frey, 2002). How would this tendon have interacted with the internal network of actinofibrils, the slender structural fibers arranged in a radiating pattern on the outer wing membrane, to manipulate the wing (Padian and Rayner 1993; Wellnhofer 1991)? Another question relates to mechanical properties of the actinofibrils, which are currently unknown, and their function in controlling membrane shape during flight.

Pterosaurs, the first vertebrates to evolve powered flight, were long thought to be primitive flyers inferior to birds and bats. This perspective changed as a result of more recent studies of pterosaur morphology and flight mechanics (Bramwell and Whitfield 1974; Padian 1983a, b, 1987, 1991; Pennycuick 1988, Hazlehurst and Rayner 1992; Padian and Rayner 1993), including the recent Stanford-National Geographic Pterosaur Replica Project. Pterosaurs evolved from small, stable flyers to much larger and more agile flying creatures. The more derived pterosaurs were more dynamically unstable in flight, and probably used subtle and sophisticated flight control mechanisms involving span, sweep, dihedral and twist variations. Modern adaptive wing designs involve similar mechanisms (McMasters and Cummings 2004; Stanewsky 2000, 2001; Inman et al. 2001; Livne and Weisshaar 2003). Perhaps pterosaurs have the most to teach us regarding possible future aircraft development, not just in adaptive wing designs, but also in the design of effective membrane wings, advances in flight control mechanisms, and designs of effective flapping flight mechanisms, particularly in flying animals of great size (the largest known pterosaur is 50% larger in wingspan than the largest known fossil bird).

Subtle changes in membrane tension can produce significant changes in the distribution of lift over a pterosaur wing. The adaptive load redistribution was likely used for load alleviation, reducing bending moments in the pterosaur structure during maneuvers and gusts. It might also have been used to reduce vortex drag over a range of flight speeds, adapting wing twist passively to improve flight performance.
Constructive application of aeroelasticity may have also been a key aspect of pterosaur control. The reduction in roll damping due to passive aeroelastic interactions is essential for lateral maneuverability of these high aspect ratio wings. The variable twist also reduces adverse yawing moments at low speeds, enabling pterosaurs to fly without large vertical surfaces for yaw control. The strongly nonlinear structural characteristics of pterosaur and other membrane wings pose challenges to existing analysis and design methods.

The wing membrane is designed to emulate the presence of actinofibrils (Figs. 6-8) and will be manufactured using modern sail-making techniques. In the course of the project, it became clear that the actinofibrils significantly alter directional stiffness of the membrane and act in compression. It is hypothesized that they had an important function in camber control. ... iption.pdf

In earlier work, Dr Wilkinson showed how the biggest pterosaurs got into a flap, solving the enduring problem of how these giants could get off the ground if their wings were tethered to the legs - a fourth finger sported a thin membrane connected to the body and the hind legs, akin to the wing of a bat.
With Prof Charles Ellington, of Cambridge, and Dr David Unwin, in Berlin, he found that the secret was a unique bone called the pteroid, which was like a thumb, only it sprouted from the creature's wrist.
The traditional view is that this bone pointed towards the shoulder of the creature, and supported a skin-like forewing in front of the arm.
Thus the forewing, which scientists called the propatagium, was slim, short and ineffectual.
However, exceptionally well-preserved fossils from Brazil of Ahanguera and its relatives indicate that the pteroid could have pointed forwards, giving a much larger forewing with a far greater range of movement, rather like the leading edge flap of a modern aircraft. ... dino22.xml
The results of this study are presented as video clips below, showing the complete, fleshed out pterosaur in the postulated gliding position and how it would have folded its wings when on the ground. Of particular note is the orientation of the pteroid bone: a spar-like element, unique to pterosaurs, that articulated at the wrist. Previous workers have generally assumed that this bone pointed towards the body, and so supported a rather narrow forewing with little facility for adjustment. This interpretation is understandable, because this is how the pteroid is oriented in articulated, flattened fossils. However, the 3D Santana fossils show that the bone could be directed forwards, in which case it would have supported a very broad forewing that could have functioned as a leading edge flap.
I tested the aerodynamic consequences of this new reconstruction by testing wing profile models in a wind tunnel in the Department of Engineering. The results were extraordinary. When standardised with respect to airspeed and wing area, the maximum lift force developed by the pterosaur wings was found to be about 25% higher than that measured for extant flying vertebrates. This high-lift capability would have enabled the ornithocheirids to glide very slowly and may have been instrumental in the evolution of large size by the pterosaurs, the biggest of which had wingspans up to 12m. The leading edge flap could also have functioned as a useful control surface in flight. ... osaur.html

Pterosaurologists have traditionally fallen into broad-wing and narrow-wing camps. However, new studies of the mysterious fibrous structures that make up the wing membrane (called actinofibrils), and the brains of pterosaurs, add a new twist. It seems that actinofibrils are actually highly specialized muscle fibers that radiate throughout the wing membrane. Studies of the pterosaur brain show a tremendous amount of volume in the areas devoted to fine muscle control. These factors make it seem likely that the pterosaur wing was not a static surface bound to a wide or narrow shape, but an incredibly dynamic muscle complex capable of subtle and dramatic changes in shape and tension.
The most conspicuous flight adaptation of the pterosaur skeleton is their wings. They are structures that share features with those of birds and bats but are anatomically unique. Like birds, the wing was comprised of a single spar formed from bones of the hand and forearm, but in keeping with bats, distal portions of the wing were supported by an enormously elongated finger, albeit only one compared to the three flight fingers of bats (fig. 3). In flight, this finger was held between 150º to 170º from the supporting wing metacarpal (one of the bones that comprises the palm of the hand) to form an elongate wing. However, when grounded, it could be folded tightly towards the body so as not to impede terrestrial locomotion. Attached to the elongate forelimb was a wing membrane known as the ‘cheiropatagium’ that extended from the tip of the wing finger to the hindlimb. Exactly where it attached on the hindlimb remains controversial as very few fossils unequivocally preserve the full outline of the wing. The best fossil evidence currently available indicates pterosaurs had broad membranes that attached at their ankles, not at their knees or hips as commonly suggested by palaeontological illustrators. However, some argue that narrow wings would have improved flight efficiency, and favour a model of knee or thigh attachment. Two further membranes complete the pterosaur wing: the uropatagium, located between the legs, and the propatagium, found along the front of the forelimb. The latter was controlled by the pteroid, a unique pterosaur bone that articulated with the wrist and controlled the propatagium as required during flight, manipulating it like flaps on a plane wing.

Exceptional preservation of pterosaur membranes has revealed intricate details of the stratified internal tissues making up these organs. The upper surface was little more than a thin epidermis, with a comparatively thick layer of spongy tissue directly beneath. Underlying this was a network of blood vessels and capillaries and a thin sheet of muscle. A complex of elongate, stiffened rods underlay the muscle tissues and strengthened the cheiropatagium, acting analogously to the fingers of bats or central vane of bird feathers. These rods were neatly arranged parallel to the wing finger in the distal part of the wing. They were shorter and more fibrous towards the body, suggesting the membrane was comparatively elastic in this region. This would have allowed flex and movement of the limbs during flapping and terrestrial locomotion, while keeping the wingtip stiff and rigid to form an efficient flight surface.
All pterosaurs share this wing anatomy, but some broad distinctions can be made between pterosaurs based on other aspects of their skeletons. Classically, pterosaurs have been divided into two groups: a series of predominately long-tailed, long-bodied and short-handed forms referred to as ‘basal pterosaurs’ or ‘rhamphorhynchoids’; and the short-tailed, short-bodied but long-handed Pterodactyloidea. As their name suggests, basal pterosaurs represent the earlier stages of pterosaur evolution and have a slightly different flight apparatus to the more advanced pterodactyloids. Along with generally shorter wings, the uropatagium is broader and supported by elongate fifth digits on the feet. The long, often stiff tail overlies this membrane and bore a vertically orientated sail or rudder (fig. 4). By contrast, pterodactyloids have narrow uropatagia and correspondingly small fifth toes (fig. 5 - opening page). Although all pterosaurs are thought to have been competent fliers, the reduction of the tail and uropatagia in pterodactyloids may indicate these forms had more sophisticated flight styles than their forebears, being less stable in the air but gaining increased agility and speed because of it. ... saurs.html

Palaeobiologists could not explain how the creatures could take off from a standing start – rather than soaring, glider-like, from a clifftop - or how they had enough lift to slow down for a non-bone-crunching landing. Yet fossilised pterosaur tracks show that they could do both.
Now a team led by zoologist Matthew Wilkinson of the animal flight group at the University of Cambridge, UK, thinks the pterosaurs used a moveable forewing. They say earlier lift calculations were skewed by misconceptions about the way this forewing moved.
The pterosaur’s wing membrane stretched between its fore and hind limbs, with the outer part of the leading edge and the wingtip supported by an enormously elongated “finger”. Three claw-like digits protruded from the wing just ahead of the pterosaur’s “wrist” joint, from where a slender bone called the pteroid articulated and supported a moveable forewing. The direction the pteroid articulated and the size of the membrane it supported have been the subject of much argument.
To see how Wilkinson’s group believe the pterosaur flew click here (3.5 Mb, AVI format). To see the wing structure click here (4.5 Mb, AVI format).
Moderate breeze
It had “extraordinary” aerodynamic properties, he says, boosting the lift of each wing by 30%. And thanks to the forewing’s steep camber, this lift was attainable at unexpectedly high “angles of attack” – the angle the wing bites into the airflow - as would be necessary from a standing start.
“Even the largest pterosaurs may have been able to take off simply by spreading their wings while facing into a moderate breeze,” Wilkinson told New Scientist. And the enhanced lift would have allowed air-speed reductions of about 15%, allowing for smooth landings.
The main part of the pterosaur wing was a thin membrane stretching between the fore- and hindlimbs and supported in front by the arm with a hugely elongated fourth finger. In front of the arm, though, was a smaller forewing called the propatagium, supported by the pteroid bone. If the pteroid pointed forward, the propatagium would have formed a broad leading edge flap, with potentially dramatic aerodynamic consequences, Wilkinson thought.
First, the researchers examined fossilised pterosaurs to make sure that it was possible for the pteroid bone to swing into a forward-pointing orientation. Facets in the joint where the small bone articulated made it clear that it could swing from pointing towards the body to pointing forwards, furling and extending the forewing.
Then they built three models of the wing with different pteroid positions - fully extended forward, partially furled, and completely absent - and covered them with ripstop nylon to approximate the wing membrane. When they tested the wing models in the University of Cambridge wind tunnel, they found that the extended pteriod conferred a dramatic advantage. The broad forewing increased maximum lift forces by about 60% and, when the wing was nearly parallel with the flow, lift forces jumped from five times the drag force with the forewing furled to about 18 times the drag with forewing extended. As the wing angled up to become more perpendicular to the flow, the pteroid continued to help - it prevented the wing from stalling out, which would cause the lift to drop to zero. Surprisingly, the forewing only seemed to help when it was fully extended; the model with the partially furled forewing performed no better than the model with no forewing at all.
Pterosaur wings 1: shape
Much has been written on pterosaur wing-shape and sadly most of it by people who have clearly not studied the material carefully enough, or understand the principle or parsimony as applied to such situations. The very short version of this is that based on the fossil evidence (and once you start cobbling together all of the available bits we have, there is actually quite a lot) for the extent and shape of the wing we are left with a pretty simple conclusion. The main wing in most, if not all pterosaurs ran from (not surprisingly) the tip of the big 4th finger down to (more surprisingly) the ankle.
Here is where the parsimony comes in as basically we have several specimens where it is absolutely certain the wing reaches the ankle. We have several more where some postmortem contraction and dissassocaition has occurred and the wing has shrunk and folded up but still reaches at least to the thing. Finally we have some that have really folded up, or like the Zittel wing are completely separate from the body so we cannot be certain at all about how big it was in life. In short we have conclusive proof that the wing was broad in some, and nothing that could contradict that as other specimens are distorted or equivocal. The situation is a little more complex than this, but that is about it and so we can only follow the evidence and that points to a broad wing in all pterosaurs. ... s-1-shape/
Pterosaur wings 2: structure
Ok, so following on from part one now we have a ‘broad’ wing with an expanded tip – now to the nitty gritty. The pterosaur wing (as I have previously stressed) is not some sheet of tough leather, but an incredibly complex organ which in many ways is actually quite superior to the equivalent structure in bats (all this ‘pterosaurs as bad fliers’ junk can go too) and would have allowed them superb control over their wings during flight. The pterosaur wing is made up of at least 5 layers and probably more. It is hard to tell as obviously looking at this kind of microstrucutre is pretty difficult and we have to rely on comparing some very different fossils, preserved in very different ways for our information. In addition to an outer epidermis (top and bottom), there are three key features that we do know in quite good detail though and these are worth spending some time over. Some of these might be duplicated (i.e. there could be two muscle layers) and so five is a conservative figure as there could be more, or other layers might interact and be less clear-cut than we think.

In terms of describing the function it is easiest to go from the bottom up – so we will start with the ventral layer. So, from the bottom (after the epidermis of course) we have a layer that consists of small blood vessels. These form a network across the entire wing, with a large blood vessel running sub-parallel to the wing finger and then branches coming off of it. Obviously these would supply the wing with blood and by extension oxygen, fluids, ions etc. to keep it functioning. But why would an essentially broad piece of skin require so much blood? Well, as I have wearily pointed out before, these are hardly bits of leathery skin, but highly advanced tissues. The blood is needed to supply our next layer – that of muscle.
The muscle layer is not like what you might immediately imagine, it is not a thick block of traditional skeletal muscle, but a delicate network of muscle fibres that spread like an misshapen net across the whole wing. Their function might not immediately be obvious – but it should be. By contracting or relaxing the muscle fibres, the pterosaurs can change the shape of the wing! Yes, they can actively wing-warp, altering the camber and thus aerodynamic properties of the wing – high lift and low steering to high steering and low lift! Flatten out one wing, the lift will drop with a low camber and the pterosaur will roll to that side. Flatten them both and it will fall into a soft glide as the amount of lift is lowered. These guys were no slouches in the air and had tricks in their wings birds and bats could only dream of!
Pterosaurs don’t have fingers like bats, or split the wing into dozens of ‘parts’ like birds, so they need to have some structure to hold the wing taught and provide lift. If it was not attached securely to the body of the pterosaur, and given some shape, it would just fold up like an umbrella without any ribs.Thus these provide a level of stiffness to the wing and in combination with the muscle layer give the pterosaur control over the wing camber and its lift.
Actinofibrils are unusual structures and we are not sure exactly what they are composed of. The best guess is collagen, but it could also be cartilage or keratin. Determining this in fossils is obviously near impossible but all three are realistic possibilities, though of course collagen is the most likely given the position of the fibres inside the wing membrane (rather than on the surface) and they do not connect to the bones of the wing finger. They lie sub-parallel to the wing towards the wingtips and then sub-perpendicular as we move more proximally. There are no actinofibrils in the proximal wing close to the body, and they get more densely packed the further away you go.
In short they are more densely packed distally and lie in the same direction as the finger, and proximally are rare or missing and lie perpendicular to the long axis of the wing. Functionally this means that the wing is quite stiff in one plane, but flexible in another (the wing membrane can concertina up when the wing finger retracts). The fibrils themselves are slightly elastic and can slide across each other where they are packed tightly tighter, which in tandem with the elastic nature of the muscles fibres makes the wing as a whole highly elastic. This means it can be quite compact when at rest and contracted, but can unfurl to a large size and remain quite rigid when necessary. ... structure/
images from: http://www.palaeontologische-gesellscha ... .html#dino

For me, looking upon all the information around, it seems that not all is yet told about how the pterosaurs flew. But that they did is certain and it is also certain they had adaptations for that function specific only to pterosaurs and that made them have distinct abillities. Although hanggliders can give general idea of what is possible in view of the amount of weight and seize needed and possible for getting in the air, they lack the special form and dynamic adaptability of their structure to fully represent pterosaurs as models.
Pneumaticity is still a factor that is not well understood. But it is a factor not to be too easily brushed on the side. It plays a role in weight distribution and structural enhancement, the measure of which is still ongoing research. The fact that pneumaticity can be seen in different organisms, more notably in the larger versions and more advanced species, is for me personally a very good argument to be very careful in too easily claiming that something could not live in gravitational field levels occuring today or needed lower gravitational levels then. As long as nature is still a model for our human flight capabillities, I still think it's wise to study well all the structural answers nature has to offer to the obstructions presented by the environment and only then one would be able , I think, to know the bounds of what can be viable in this gravition field level (not including chemical constitution differences of the athmosphere).
As for more distinctly pterosaur adaptations, I personally think the way the structural make-up of the wingmembrane shows the uniqueness of the pterosaurs. The still not well understood structure and function of the membrane, allready shows signs of a fully controlled adaptive structures capable of extension and contraction as well as elasticity and rigidity. And with that abillity the pterosaurs had profound flightcontrole unmatched by human technology and even birds and bats. Also the pteriod and it's structural function in a collapsable front wing gave me the idea that also here an important factor can be present that is not well understood. The significant positive effects shown in models give rise to possibilities sometimes not well taken account of on the level of flight capabilities.

So once again I think it is fair to state that it is unwise to use this size of animals as an argument or proof for a changing gravity. All these creatures that are deemed as too big, made use of principles and structural solutions that can explain why they were as they were. As, I personaly think, with astronomy as soon as certain structures and functions, as plasma (and biology is plasma in a sense), are not taken account of, then the only thing that remains is postulating fudge factors like dark matter or maybe a changing gravity for organisms.
If the large-organism-isn´t-possible-argument is used as to provide proof for a changing gravity one will come into difficulties. For as it seems one will also have to provide reasons for why a changing gravity has no effect on organisms as no effects are present in the present record concerning organisms. There is no problem with creatures in the past, only a problem with not being open to new information out of fear of contradiction with the model one is holding. Here I´m not saying that gravity can not change or the earth has not grown. Maybe both do apply or one or maybe even both do not, I simply don´t know. Just as I know next to nothing about aerodynamics or organisms and for that matter plasma, but we have to apply certain principles or get to learn and understand them, and when we do, sometimes things may be less phantasical than we thought and more simple and beautiful than we had seen.
The illusion from which we are seeking to extricate ourselves is not that constituted by the realm of space and time, but that which comes from failing to know that realm from the standpoint of a higher vision. -L.H.


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