see text Sea pens are marine cnidarians belonging to the order Pennatulacea, which are colony-forming benthic filter feeders within the class Octocorallia (subphylum Anthozoa).

Those belonging to the much larger suborder Sessiliflorae lack feathery structures and grow in club-like or radiating forms.

[4] The order Pennatulacea consists of the following families:[5] Due to their wide geographic distribution and long evolutionary history, genetic variation within the different species of sea pen is quite large.

Rarely found above depths of 10 metres (33 ft), sea pens prefer deeper waters where turbulence is less likely to uproot them.

[8] They position themselves favourably in the path of currents, ensuring a steady flow of plankton, the sea pens' chief source of food.

Like other anthozoans, sea pens reproduce by coordinating a release of sperm and eggs into the water column; this may occur seasonally or throughout the year.

Fertilized eggs develop into larvae called planulae which drift freely for about a week before settling on the substrate.