A phylum of coelomate (see coelom) worms that lack body segmentation. Like Echiura, they are cylindrical in shape, and the mouth is surrounded by small tentacles. They have a long, U-shaped gut with the anus lying on the anterior dorsal surface. The nervous system includes a brain, and sense organs are present. Males and females occur. They are exclusively marine, all live near the sea-bed, and most feed on detritus, although some are carnivores. They are first recorded in the middle Devonian.
Subjects: Zoology and Animal Sciences — Ecology and Conservation.