There are several different morphs. I had one that was entirely purple and currently have 2, one is entirely green and the other has a purple base and appears to have green heads. To my knowledge they are all the same thing, similar to different zoa morphs. The only place I have seen a duncan listed under anything differently was on saltwaterfish.com having a duncan and a duncanopsammia under their SPS
section, even though it is even labeled an SPS
. But the scientific name is Duncanopsammia axifuga for all I've seen.