Four Limbed Take off

[ttyo888]

Hi I am just wondering how do pterosaurs take off from the ground using all four limbs.

 

http://blogs.ngm.com/blog_central/2009/08/pterosaur-takeoff-.html

 

I still had some doubts so I decided to animate the thing in my computer graphic program.

 

Becos I have a creature design project that needs a creature that can take off using 4 limbs. I need some guy from a scientific viewpoint to see if my animated creature seem plausible.

 

This one is for smaller species... This one is based on references of smaller birds which take off immediately from a standing start. Also smaller species have a lot of wing flapping.

 

This one is for bigger species.. Becos it's heavier than the small one, it will take jumps before take off. The number of jumps and runs required will increase with the size of the species... the 8 m wingspan species will need about 3-4 hops before it takes off.

[Mokele]

I've met the guy who came up with this, actually - he gave a talk on the topic. Unfortunately, the paper is in some obscure journal without much online presence.

 

Your animations have a few problems, and I'll take them in order.

 

First, for the small one, it looks like the feet come up, then 'stomp' in order to push off, with not real change in torso height. In actuality, birds taking off crouch low to the ground (how low varies, and it's a very quick movement), then push off their legs as the wing swings up. The feet have completely left the ground before the wing even begins with swing down.

 

For the big one, the wings/arms aren't moving through a great enough angle when on the ground, giving it a very stiff appearance. It should be one movement, no running start, and it should vault over the forelimbs like a pole vaulter, with a large change in torso height during the movement.

[ttyo888]

Ok Here's the second version

 

Small

 

Large

[Mokele]

The small one looks much better now. There's still something not quite right about the big one. It seems as if the legs are just sort of stomping the ground uselessly, causing the body to pivot at the shoulder without any real benefit. The forelimbs/wings also don't move very much.

 

I think a key issue is how to think of limbs. Imagine a line from the shoulder to the ground contact (foot, hand, toe, whatever). This is the "effective limb", and it functions as an extensible strut. it can do two things, pivot and change length, and all movements are some combination of the two. A walking human uses their legs mostly as a fixed-length strut, pivoting at the hip to produce motion, while a jumping human (from a standing start) uses their legs mostly by extending the "effective leg" without much angle. Running human legs are a mix.

 

For the large pterosaur launch, consider the back "leg-struts" as mostly extending (via changes in joint angle), while the "wing-struts" stay a mostly fixed length and rotate (the angle of rotation should be large, maybe 80 degrees or so). The back legs push off, and the body "pole-vaults" over the wings. Once it begins to arc downwards (past vertical for the "wing-strut"), the wings flip up and then beat downwards.

[ttyo888]

OK thanks Mokele

 

I hope this animation will not only help Animators but also Scientists too.

 

Okay here's the 3rd versions... but do note that this animations are based on "ground up", They will not apply much if they are dropping from a cliff or a tree branch.

 

 

[Mokele]

Looks a lot better, IMHO. The big one looks quite cumbersome, which is actually very accurate - pterosaurs were probably pretty clumsy and awkward when on the ground.

 

And yes, trees and cliffs change things a lot, especially if they can just drop to get the speed, then glide away.

[ttyo888]

Finally someone upload the video Nat Geo took down

 

Quadrupedal Launch

 

But can the same technique be used on water like the same way ducks and swans take off from water surface. Can these creature run on water on fours rather than on twos or will they sink like a stone?

[Mokele]

Sink like a stone - birds can only get away with it because their legs are uncoupled from their wings. Bats, for instance, cannot launch from the water (though apparently they can swim).

[ttyo888]

Oh I see unless the Pterosaur has long legs to run on walk on the water like a water bird.. otherwise it will sink like a stone.

 

But this will limit the size limit of the species but I guess that's okay since swans are pretty impressive size.

 

This will also mean that the wing fingers will be atrophied.. Sounds like one of the Pterosaurs; the Nyctosaurus whose wing fingers are either missing from the fossil record or it's atrophied.

[Protoart]

There was a discussion of this in the "Dinosaur Mailing List" in June of '08. You might want to read it.

http://dml.cmnh.org/2008Jun/msg00141.html

Edited December 18, 2009 by Protoart