Urchin eating acro?

[SFREEF3R]

I can't tell if my short spined urchin was eating my Red Planet acro or it just bulldozed into it, but there a semi-circular chunk now missing from it that wasn't there yesterday. I do have some Eunicid worms in the tank (though none that hang out near this acro), so that probably would have been my first guess if I hadn't seen my urchin suspiciously close. I have read other reports of urchins eating coral (searched after witnessing this), which is totally news to me. I had previously thought these species were strictly herbivores and totally reef safe.

A picture from a couple weeks ago:

 

[vetteguy53081]

Some may go after zooxanthelle which causes damage

 

[ihavecrabs]

Some may go after zooxanthelle which causes damage

Terrifying.. I have three in my SPS dominated tank haha

 

[ppatches24]

My urchin ate my clove polyps. It's gone now.