Putting some meat (and membranes) on Nyctosaurus

Figure 1. The UNSM specimen of Nyctosaurus, the only one for which we are sure it had only three wing phalanges.

Figure 1. The UNSM specimen of Nyctosaurus, the only one for which we are sure it had only three wing phalanges.

The UNSM 93000 specimen of Nyctosaurus (Figs. 1-3), in the University of Nebraska State Museum, would have been complete and articulated, except for a small channel of erosion that cut through the skull and limbs before discovery. Nevertheless the post-crania is intact (Fig. 2) and a little cutting and pasting more or less reproduces the in vivo look of the specimen in dorsal view (my what big arms you have!).

So here it is.
Every 5 seconds the scene will change with 3 scenes total (including the blend). The hind limbs are in the flight position, acting like horizontal elevators on an airplane and like little wings able to provide lift for the hind limbs. The fuselage fillet is shown. Otherwise the wing finger and its trailing membrane (brahiopatagium) is stretched only between the wing tip and elbow with no hind limb connection. That makes a short chord wing, just like a sailplane.

Figure 1. Nyctosaurus GIF movie showing in situ and in vivo versions of the post-crania. Membranes (uropatagia and fuselage fillet) and muscles added.

Figure 2. Nyctosaurus GIF movie showing in situ and in vivo versions of the post-crania. Membranes (uropatagia and fuselage fillet) and muscles added. Note the axis of the femoral head is aligned with the axis of the acetabulum. Nyctosaurus has hind legs like those of Sharovipteryx. Note: only the deltopectoral crest of the right humerus is preserved and it was flipped during taphonomy.

This specimen of Nyctosaurus is the only one that had but three wing phalanges. Evidently none were lost distally as m4.4 is often curved in pterosaurs as it is here (Fig 3). Rather m4.2 and m4.3 appear to have fused into one long bone. No Nyctosaurus shows a shortening of either of these two bones, so one did not disappear. A tiny ungual completes the wingtip, by the way.

Standing model of Nyctosaurus by David Peters

Figure 3. Standing model of Nyctosauru based on UNSM 93000. This one did not have a crest.

In figure 2
note the length and shape of the posterior dorsal ribs. They don’t curve much. Nyctosaurus might have had more of a pancake-like (rather than sausage-like) posterior body to match its wide chest, as seen elsewhere in Sharovipteryx, Eudimorphodon and Jeholopterus. In UNSM 93000 the sternum remains buried.

On a side note:
For those interested in some VERY bizarre Nyctosaurus reconstructions by artists like Jaime Headden, Mark Witton, Matt Martyniuk and others, click the following links:

  1. Nyctosaurus-sebulbai
  2. nyctosaurus.png
  3. nyctosaurus_skeleton_crested.jpg
  4. pterosaur_quad_launching_by_gaffamondo-d7ve3di.jpg
  5. alternative_diagram_for_quadrupedal_launch_by_gaffamondo-d7xagyk.jpg
  6. Witton_crested_nyctosaurs_March_2009.jpg

Note:
the tall thin crests are NOT the bizarre aspect of these illustrations and sculptures. The crests, in some specimens only, are real (Fig. 4).

On the quad launch issue (see illustrations from the list above),
remember that no pterosaur ever impresses metacarpal 4 (the big one) into the substrate. The tiny fingers are all that are ever impressed. Furthermore, as noted earlier, the quad launch hypothesis has many problems solved by simply taking off like a bird does.

Not immediately apparent,
some of the above images by other artists also appear to abbreviate the big metacarpal 4 for artistic purposes.

Figure 5. The derived Nyctosaurus, KJ2 in a floating configuration using its long forelimbs as pontoons.

Figure 4. The derived Nyctosaurus, KJ2 in a floating configuration using its long forelimbs as pontoons. With hollow wing bones, this pterosaur might have floated a little higher on the surface, but it’s hard to judge with the weight of that big crest and skull pressing down. It is also easier to draw the forelimbs in this fashion, rather than out laterally, yet still folded, which would have been quite stable with those metacarpal pontoons, probably floating diagonally to laterally on the surface.

References
Brown GW 1978. Preliminary report on an articulated specimen of Pteranodon (Nyctosaurusgracilis. Proceedings of the Nebraska Academy of Science 88: 39.
Brown GW 1986. Reassessment of Nyctosaurus: new wings for an old pterosaur. Proceedings of the Nebraska Academy of Science 96: 47.

wiki/Nyctosaurus

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