No they look like a type of palythoas. I would however, be careful as they can take your tank over in no time flat. Zoanthids and Palys multiply by what is called budding. So theoretically they multiply like so (1,2,4,8,16,32,64,128) etc... They usually grow a little slower than that, but you can see where the problem lies.
They look cool, but as I said I would have very keen eye on them as if they start choking other corals out, they will become a problem quickly.