And finally there's expulsion, where the anterior shoulder slips under the symphysis pubis, followed by the posterior shoulder, and then finally followed by the rest of the body.
After the delivery of the head, there's restitution, where the head externally rotates so that the shoulders can pass through the pelvic outlet and under the symphysis pubis.
Even with such teeth, plant mater is difficult to digest and their backwards pointing pubis gave ornithischians the extra belly room that they needed for a large digestive tract.
And that's because the muscles rearrange themselves because they're not moving in the same kind of way and so in an Ornithischian dinosaur, the pubis reorientates itself so that it's back beside the ischium.