Doing without both skeleton and sclerites leaves you as a worm-like tubular coral, with frilled filter feeding equipment at the top, and a bulbous, anchoring foot at the bottom, which makes some of you look a little like old fashioned quill pens.

You prefer to live in smooth-flowing deep water, with a deep sediment for you to bury your foot in. If you find there isn’t enough food where you are, you can let go, and float to a new location, where you will anchor.

You are unusual in the modern world in that your body exhibits ‘glide reflection’, where your features are arranged symmetrically, but one side is shift up or down slightly.

You live quietly in seas all over the world: you are a Sea Pen.