[PatrickHenry]

Notably, the “no new body plans” mystery is a concern among scientists as well.

I agree that this is interesting, but I don't know if it "rises to the level" (Clintonian expression) of a serious concern. To put the issue a different way, we might well ask why no new hominid has emerged in the last 5 million years. There were a few, very few, and now there are no new ones to be found. Is this a problem for evolution? I don't think so. It's just an observation of what's developed. The domain of what hasn't developed is infinite, but I don't see the need to worry about why each possible development hasn't appeared.

[Alamo-Girl]

Thank you for your reply!

The domain of what hasn't developed is infinite, but I don't see the need to worry about why each possible development hasn't appeared.

I'm not getting concerned over every little missing thing - just pointing out that there have been virtually no new phyla since the Cambrian explosion and that fact may be related to eyeness developing across phyla concurrently. IOW, the regulatory control genes may control the freedom of movement after the Cambrian explosion.