: Includes sea anemones and stony corals. They typically have tentacles and mesenteries in multiples of six.

Historically, Actinozoa was divided into two main groups based on their symmetry and tentacle count:

: The body consists of a central gastrovascular cavity divided by vertical partitions called mesenteries or septa. These mesenteries increase the surface area for digestion and support the gonads.

: Includes soft corals, sea pens, and sea fans. They strictly possess eight branched (pinnate) tentacles and eight mesenteries. Ecological Importance

The name Actinozoa stems from the Greek words aktis (ray) and zoon (animal), referring to their radial symmetry and the "ray-like" appearance of their tentacles.