[1] Ceriantharians were formerly classified in the taxon Ceriantipatharia along with the black corals[2] but have since been moved to their own class, Ceriantharia.

The outer whorl consists of large tentacles that extend outwards.

[3] The tentacles of Ceriantharians are also venomous, similar to Cnidarians, which allows them to protect themselves from predators.

[4] A few species such as Anactinia pelagica are pelagic and are not attached to the bottom; instead, they have a gas chamber within the pedal disc, allowing them to float upside down near the surface of the water.

[5][6] A 2020 integrative study incorporating molecular phylogenetic reconstructions and morphological assessment across the three families recovered Arachnactidae as a well-supported clade, but did not recover Cerianthidae and Botrucnidiferidae as monophyletic, drawing into question the validity of the Spirularia suborder[10] Hickman; et al. (2008), Integrated Principles of Zoology (14th ed.