Cambrian to Recent
These animals have an eight-fold symmetry. Most are colonial sessile polyps. Octocorallia look like the stony corals. Stony corals have a six-fold symmetry, and are classified in the group Hexacorallia. Unlike the stony corals, most Octocoralllia lack a lasting skeleton. For this reason, they do not build coral reefs. An older name for this group is Alcyonaria.
Many species form symbioses with unicellular algae. Octocorallia have many enemies: For this reason, many are toxic, or they taste bad. Many species of the Octocorallia can reproduce both sexually and asexually: It is common to find a colony of Octocorallia, where most polyps have the same sex.