Well, not “hoof” exactly. But they do move.
This is a shot looking straight down on a sea urchin. And you may notice that in addition to the nice zebra striped and big spines, it also has lots of thin very brittle (key point) spines. You can see a bundle of them pointing from the center to the upper left corner of the picture.
And yes, very brittle. I was taking a picture of something else and I must have gotten just a little too close. When I pulled the camera away to chimp, I noticed that I had a clump of those thin spines poking out of my left arm. People make fun of me for wearing extra thick neoprene. (I joke that if they made fur lined wet suits, I’d go for one. Hey, I get cold.) But one more benefit of the extra thickness is that the spines were stuck in the suit, not in me. A couple of minutes of extracting and I was back in business.
Dive site: Molokini – Reef’s End, Maui, Hawaii