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!
First we’ll colorized the sacral verts (Fig. 2).
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.
Finally, we’ll colorize the two femora.
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.
Cleaning up mistakes is the process of Science.
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