[Lawtan]

Essentially, both are Cnidarians...but it was thought for some time that Haootia exhibited Neoteny - keeping features from the sexually immature stage into adulthood. Some species do this for an evolutionary benefit - it allows them to fill a niche and compete not with the adults, but the children of a competing species.

This is a better polyp picture:

...I'll note that this thought is not certain. Haootia is only known from a few samples from over 500 million years ago, and information changes rapidly as more is gathered/found.

Still...neat?