Sea pen

Sea pens are marine cnidarians belonging to the superfamily Pennatuloidea. They are fleshy colonial organisms anchored to the seabed, with tiny polyps embedded in a soft matrix. They have a cosmopolitan distribution, being found in tropical and temperate waters worldwide, from intertidal shallow waters to deep seas of more than 6,100 m (20,000 ft).

The earliest accepted sea pen fossils are known from the Cambrian-aged Burgess Shale (Thaumaptilon). Similar fossils from the Ediacaran may show the dawn of sea pens. Precisely what these early fossils are, however, is not decided.