A phylum of coelomate (see coelom), marine, worm-like animals in which mature individuals lack metameric segmentation. The body consists of a sausage-shaped, cylindrical trunk and an anterior, muscular proboscis that cannot be retracted (unlike the introvert of Sipunculida which Echiurida otherwise resemble in size and shape). Parapodia are absent in most forms. All have a pharynx. The nervous system is similar to that of Annelida, but there are no special sense organs. Males and females occur. They are exclusively marine, and most are burrowers and detritus feeders.
Subjects: Zoology and Animal Sciences.