Echiurans are closely related to the annelids and were included in the Phylum Annelida. There are about 150 species of Echurians also known as Spoon worms and Innkeeper worms. Unlike the Annelids they have no segmentation of their bodies. They have a worm-like body with a large flattened proboscis projecting forward from the head.
Most spoon worms are suspension feeders eating mainly detritus, pushing their proboscis out of their burrows, with the gutter projecting upwards. Edible particles will then settle onto the proboscis and a channel, lined with tiny beating hairs (cilia) pushes the food into the digestive system. Their digestive system is a highly coiled tube with both mouth and anus.
Their nervous system is made up of a brain near the base of the proboscis and a ventral nerve cord running the length of the body. They do not have a distinct respiratory system, absorbing oxygen through the body wall by diffusion.