Monday, February 11, 2008

Speaking of pterosaurs...

Nemicolopterus crypticus was just announced at the National Geographic website. It's a smallest pterosaur ever found (check out the pictures, including the skeletal restoration) and will be published in the Proceedings of the National Academy of Sciences tomorrow. If the paper is not open-source, could one of you kind readers send me a copy? This is a pterosaur I need to restore!

UPDATE: Thanks to Nick Gardner for sending it to me. If you ever need a paleo-related picture, brother, let me know!


Nathan said...

Hmm, pointed wingtips, wing surfaces terminating above the knee... There's still lots of work to be done educating NG illustrators.

Zach Miller said...

After I thoroughly read the paper, Nathan, I intend to post my own restoration of the little bugger. According to Unwin's "Pterosaurs of Deep Time," the main wing surface should terminate at the ankle, but I can see why Nemicolopterus was restored with a more freed-up leg--the authors of the paper suspect it was largely arboreal.

Mike S said...

Nathan, Zach,

The illustration in question was done by yours truly, not an "NG" illustrator ( although they screwed up my name in the line credit ), in direct collaboration with Alex Kellner. While certain species of pterosaur may extend wing membranes to ankle, there is a degree of implied variability according to habitat and lifestyle.
In large azhdarchids, (Jim Cunningham, an aeronautics engineer and pterosaur researcher )is convinced the wing membrane terminates with no hindlimb attachment whatsoever.

Zach Miller said...

So it would have terminated at the...pelvis? Above the hindlimb? That's interesting.

Nathan said...

Mr. "Skrepnickaption": I sincerely beg your pardon.

Anatomical quibbles aside, the painting is very pleasing as a painting, zoologically, botanically, and compositionally, in the grand tradition. I'm curious, though: wings folded ventrally?

A feature I notice common to reconstructions of pterosaurs of all types is a sort of self-satisfied look. Does it mean "I can fly and you can't"?

Zach Miller said...

Hahaha...well, wouldn't YOU be thinking that if you could fly? I certainly would. Maybe this particular pterosaur hasn't had a run-in with a bird yet!

I have also wondered how a pterosaur folds its wings when grounded. Very problematic to me is the orientation of the joint between the wing metacarpal and first phalange. I have seen the folded wing reconstructed a number of ways.

Mike S said...

Zach - essentially yes,terminating at the pelvis, seems odd to restrict wing area in such large animal, but this was the opinion expressed.
Nathan - I've been called worse than an Ng illustrator :o), no worries!
As to wing orientation, if I take your meaning, the forelimbs in this posture are splayed horizontally and rotated forward at the glenoid (note the bottom of the manus face forward as it grasps the branchlet, putting the wing in a horizontal plane relative to the body, as if in flight, except that as the arms are partially collapsed,the wing finger is not in extension. If it were standing on a substrate, the forelimbs would be rotated and dropping ventrally ( 90 degrees to the plane they're currently in ) in order to place the toepads on the ground beneath, first 3 digits pointing outwards, whereby the fourth digit would then attain a subvertical orientation and fold further medially, into the body. I've also folded the membrane, as I'm not sure there would be enough elastin to accomodate full extension under tension and yet contract fully when relaxed without buckling. . . artistic liberty to a degree, but again, Alex had no problem with the interpretation. I hope this is a little more clear than mud. It's a bit complicated to resolve 3 dimensionally, I hope the intended perception in the artwork is not obscure / does not stray too far from the mechanism as I understand it.
The look is maybe a projection of intelligence, at least in respect to the majority of the local population !
Zach - as mentioned, it is complicated to envision how the joint articulations in the forelimb work in concert without a 3d working model. I hope to do more work on this in future ( I'm far more comfortable restoring dinosaurs ), but this was an interesting challenge.

Nathan said...

I think I see... in its unnaturally splayed posture (the better to expose its anatomy!) the wingtips are rotated forward, but in a more normal squirrely stance they would point up and back.

If it makes you feel any better, they misspelled "ginkgo", too. Also, "pterodacytl", in the title, probably shouldn't have been capitalized, since it's not a proper name.

So, does "local population" refer to us, or to its contemporaries?

Zach Miller said...

Thanks for the explaination, Mike. You're right--without the use of a 3D model, getting those joint orientations right is a real challenge with pterosaurs. Dave Hone explained it as basically the wing finger folds the opposite direction (away from the palm) as the clawed fingers. But then the wing phalanges themselves would "curl" upwards during flight? See, it's just hard to imagine. I need to make a 3D model, maybe with wire and clay.

Mike S said...

Nathan - Let me put it this way, the sense I wanted to elicit was of a small "arboreal" creature, perched precariously amongst gracile branchlets of the ginkgo (smaller and much more delicate than N. American ginkgo)... Alex liked the idea of it "swaying in the breeze ". Most vertebrates have more "range of motion" throughout there anatomy than we often give them credit for, so rather than adopting a posture, that one would readily recognize as typical for a pterosaur that is "grounded", I wanted to play with it a little...(maybe "unusual rather than "unnatural"?)

Spelling errors and twisting of facts, all par for the course, when dealing with mainstream press!, I was referring to Mesozoic contemporaries...

Zach - Correct... Dave Hone has it exactly right. The excursion of the proximal joint of the wing digit is in "opposition to the first 3... It is a bizarre organization to contemplate. Use yourself as a model to work out the forelimb mechanics, pretend you are a pterosaur in flight by doing the following . . .
1 - bend over, body held in a horizontal plane (as if in flight)
2- extend your arm out along the same horizontal plane, upper arm sub-perpendicular to the axis of your body, bent at the elbow so that your lower arm points out and away from your body
3- now supinate, so that the palm of your hand and fingers face forward
4- at this point, I would come along, attach a wooden splint to your ring finger and hyperextend it ( dislocating at the metacarpal joint ) effectively simulating the wing digit
5- remove pinky with circular saw to complete the effect (optional)

So, as a "result, the "palm" (likely a patch of thickened integument / callus at the distal end of the fourth metacarpal) and first 3 reduced digits face "palm surface" forward, as the animal flys.