Wednesday, March 12, 2008

Nyctosaurus 2.0


First of all, a thousand thank-you's to everyone who commented on my previous attempt at Nyctosaurus. Your comments on the post itself, as well as your emails (which, in some cases, included the relevant literature) helped to improve my understanding of this strange pterosaur a million times over. Perhaps of most help, however, were the skeletal drawings of Nyctosaurus by Chris Bennett and John Conway, accessable here and here. John Conway is some kind of god among paleo-artists; his measured drawings are, dare I say, authoritative. Bennett's picture is initially comical until you realize the ridiculous length of the wing metacarpal. Here are some things I learned while re-drawing Nyctosaurus based on various sources:

1) I knew that Nyctosaurus had lost its first three fingers, but I didn't realize that it had lost the first three metacarpals. In their place are ossified tendons which (as far as I can tell) ran from the pteroid to the distal tip of the fourth metatarsal.

2) Nyctosaurus has ridiculously short legs, or perhaps ridiculously long arms. Bennett's restoration of a vertically-oriented "naked lizard" is very nearly required for this beastie to shamble about on the land. This was clearly not an animal that spent a lot of time on the ground. Still, Chris' picture cannot be "final," because the amount of weight in front of Nyctosaurus' chest in an upright stance would cause it to constantly tip forward.

3) In attempting to figure out a more traditional quadrapedal posture, I kept the feet on the ground and angled the body upward in such a way that the ridiculously long arms could touch the ground without lifting the hindlimbs off the ground. Even in the resulting position, however, I am stupified as to how the creature moves forward.

4) The possibility exists that Nyctosaurus kept its arms in a sprawling posture while on the ground, so that more distance existed between its knuckles than between its feet, but this would make for a very wobbly structure, especially with that enormous head.

5) Look at the size of that freaking head! It's not enough that the skull is twice the length of the body, but the crest is almost three times the length of the skull! While sketching the whole animal (crest and all), I began to wonder if maybe the crest grew to such an extreme size to counterbalance the enormous head.

6) Nyctosaurus only has three wing phalanges, and the third phalange is strongly bent, like a very wide "V." Intuition tells me that this indicates a narrow cheiropatagium, perhaps terminating at the knee. Conway's illustration has the cheiropatagium terminating at the back of the ribcage, but somehow that just looks "wrong" to me. Personal preference, I admit.

I am still unsure of how to restore the "knuckle." An epidermal pad is still attractive, but wouldn't a tough pad like that interfere with the folding and unfolding of the wing finger? But if Nyctosaurus just had a tough knuckle, wouldn't the forelimbs be unsteady on the ground? And I apologize for the sketchy feel of this picture, but it really is just an inked sketch. I drew it this morning during my meds routine and thought it was good enough to not immediately crumple up. Rough though it may be, I feel it's a marked improvement over the last draft, because it incorporates many more reference materials.

Again, comments (no matter how severe!) are always welcome. And for that crest...I think I'm gonna need a bigger canvas!

5 comments:

Jerry said...

and the third phalange is strongly bent

Minor point: there's no such thing as a "phalange." It's "phalanx." Just FYI! The pic is great...it's always nice when evolution can produce an animal with arrows leading to the rest of it's body. ;-D

Christopher said...
This comment has been removed by the author.
Christopher said...

Wow, if I didnt know better I would say that was by a different artist than the last one. Great job.

The quadrupedal posture is very well done. And yes, the humeri would have stuck straight out laterally when on the ground, and this goes for, at least, all pterodactyloids, but probably all pterosaurs, as well. When you look at the tracks the hand prints always lie outside of the foot prints. I guess it would have walked like it had broom handles tied to its wrists.

The terminal wing phalanx is preserved in one of the two specimens, and its is strongly curved as John shows, but it isnt always such. The curvature of the terminal wing phalanx can very from almost straight to quite bent looking. Pteranodon shows this pattern as well so it could be widely spread among pterosaurs.

On the relative size of the skull, where the skull is roughly equal to or exceeds the length of the entire axial column, Ive noticed this often as well, especially among the ornithocheiroids.

The brow ridges (at least thats what it looks like) are a little weird, no pterosaur has such a structure to my knowledge. With the obvious exception of the antler, the frontals were basically flat though slightly arching over the orbital area.

Go here http://tinyurl.com/3dm4dx and play with the "Roll" movie and you can easily get a feel for what was happening. It is a specimen of Anhanguera but the sukll of Nyctosaurus was not very different, both were ornithochiroids. The most noticible difference is really only in the shape of the jugal and in how steeply inclined the premaxilla is in Anhanguera, other wise the skulls are very similar in its structure and makes a good model.

The base of the antler in your reconstruction needs to be beefier and not quit so posteriorly inclined, Id say curve it anteriorly by about 4 or 5 degrees.

The wing membrane could sinch up pretty tight when the the wing was folded, take a look at specimens of Pterodactylus that show trace of the brachiopatagium.

Well, thats it I think... sory for the book

ScottE said...

Coolness! (I wish Euparkeria were coming along half so well...)

Lucia said...

Is it possible that Nyctosaurus didn't walk, but only swam or flew? The only reason it'd really need to come to land would be to nest - so what if it was viviparous? Looking at the structure of known pterosaur eggs, viviparity should be possible.