Revision to earlier mistake on Darwinopterus pelvis

Earlier I misinterpreted the pelvis and prepubis of Darwinopterus robustodens (since revised). Here (Figs. 1-5) I want to take you through the DGS process that more accurately identifies the elements present. Here (Fig. 1) is the in situ fossil. The original reconstruction, you might recall (Fig. 5) found a very deep pubis and a very shallow ischium opening, hardly enough to squirt out a turd, let along an egg!

Figure 1. The pelvic area of Darwinopterus robustodens in situ.

Figure 1. The pelvic area of Darwinopterus robustodens in situ. The ilium is easy to see. The ventral pelvis can be confusing at first glance. Here’s where DGS really shines.

First we’ll colorized the sacral verts (Fig. 2).

Figure 2. Darwinopterus robustodens sacral vertebrae in red.

Figure 2. Darwinopterus robustodens sacral vertebrae in red.

Then we’ll find the left and right pelvic and prepubic elements (Fig. 3). Note how the rear prepubis provides the illusion of a continuous ventral pelvic rim. The left pubis is folded back onto the medial left ischium, thickening it. Compared to other Darwinopterus specimens, the prepubes are flipped here.

Figure 3. Darwinopterus robustodens pelvic and prepubis elements. Note the left pubis is folded back on top of the left ischium. The rear prepubis fills a nice gap that makes the elements look like a single element.

Figure 3. Darwinopterus robustodens pelvic and prepubis elements. Note the left pubis is folded back on top of the left ischium. The rear prepubis fills a nice gap that makes the elements look like a single element.

Finally, we’ll colorize the two femora.

Figure 4. The two femurs of Darwinopterus robustodens

Figure 4. The two femurs of Darwinopterus robustodens

Pulling the elements out of the tracings (Fig. 5) provides a more plesiomorphic pelvis with an ischial opening large enough to pass a Darwinopterus-size egg.

Figure 5. Darwinopterus robustodens pelvis as originally reconstructed (gray scale) and as recovered using DGS (color).

Figure 5. Darwinopterus robustodens pelvis as originally reconstructed (gray scale) and as recovered using DGS (color). I wonder whether the present orientation of the prepubis is correct. but it seems to fit better both here and to match with sister taxa when flipped like this.

Cleaning up mistakes is the process of Science.

References
Hyder ES, Witton MP and Martill DM 201X. Evolution of the pterosaur pelvis. Acta Palaeontologica Polonica 5X (X): xxx-xxx. http://dx.doi.org/10.4202/app.2011.1109

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