Not sure but I remember seeing a thread on RC a long while back about something very similar. Maybe post the pic there if ya don't get any info here.very weird looking.
IJO showed this to me today, and I've never seen anything like it either....and I keep all kinds of stuff from the zooanthus family.
It appears to be a "matting" coral, but what you see in the picture, is actually "open", so I'm thinking it is maybe some type of sponge, rather than a coral?
About half way down...
Compound ascidians are the smallest tunicates. Generally, these form large colonies which are embedded into a common tunic. These colonies may either encrust dead or living surfaces. The siphons are numerous and are common to the colony. In some species, such as the condominium tunicates, the outward appearances may also give the semblance of a sponge.