Raising the neck and bending the knees on Zhejiangopterus

Mark Witton recently revised his reconstruction of Zhejiangopterus (the most completely known azhdarchid, Fig. 1). Witton raised the angle of the torso, raised the neck and moved the hands and feet closer together. Now the pteroid is correctly articulated to the radiale. The fingers are correctly oriented laterally. The pace has been corrected to match known azhdarchid tracks (Fig. 1). That’s all good.

Figure 1. Click to enlarge. Zhejiangopterus according to M. Witton, before (above, in silhouette) and after raising the neck (outline drawing). Now the reconstruction better matches tracks (below) and better matches the reptileevolution.com stance (black and white reconstruction at right). Still need to use the correct pelvis and prepubis and bend the knees in Witton's drawing.

Figure 1. Click to enlarge. Zhejiangopterus according to M. Witton, before (above, in silhouette) and after raising the neck (outline drawing). Now the reconstruction better matches tracks (below) and better matches the reptileevolution.com stance (black and white reconstruction at right). Still need to use the correct pelvis and prepubis and bend the knees in Witton’s drawing to match the Cai and Wei 1994 tracing of the in situ fossil.

A few minor quibbles
Witton needs to bend the knees of his reconstruction to match the in situ fossil reported by Cai and Wei 1994 (Fig. 1) and really, every known articulated pterosaur. Sure this pterosaur was big, but it did not have graviportal limbs and Witton’s reconstruction misses the distal articular surfaces of the femur. The femur has a distinct curve not shown by him. Witton needs to employ an azhdarchid pelvis, not a tapejarid type. Metacarpals 1-3 are not shown in Witton’s reconstruction. Metacarpal 4 is much too robust. The radius and ulna are too long, and the humerus is too gracile in Witton’s reconstruction. A strict tracing is called for here, not a freehand pencil sketch.

Pterodactylus walk matched to tracks according to Peters

Figure 2. Click to animate. Plantigrade and quadrupedal Pterodactylus walk matched to tracks. Zhejiangopterus would have had a similar walking pace tied to its own tracks in which the manus more closely followed each pes track (see fig. 1).

Walking pace improved
Witton’s old reconstruction (Fig.1 upper left) placed too much weight on the forelimbs. His new reconstruction permits the feet to be placed beneath the shoulder joint, the center of balance in pterosaurs. This permits the forelimbs to be raised like ski poles in preparation for a flight that commences with a hind limb leap or run and a series of powerful wing flaps. In other words, it’s much easier in this configuration to become bipedal because the toes are beneath the shoulders.

You can see an animation of the Pterodactylus walking pace matched to tracks in figure 2 for an example of how pterosaurs should fit their tracks while bending their knees.

Advertisement

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.