I think its a baby developing ricordia. They can grow from just a tiny bit of left over foot flesh if one was removed. The bare area around those zoos look about the size of a big one.
it closed up when i tried to feed it a mysis shrimp... of course it wasnt the best because my dumb shrimp kpt getting invovled....nosey little jerk,lol.
Closes, :notsure: Withdrawls into a skeleton like a LPS or into a ball like a soft coral polyp ? I know you said it has a hard outside.
Can you post a pic of it closed ???