Peanut Worm

The Sipuncula, or Sipunculida, commonly called sipunculid worms or peanut worms, is a class containing about 162 species of marine worms that have secondarily lost their segmentation. Sipuncula was once considered its own phylum of unsegmented worms but was demoted to a class within the phylum Annelida based on molecular evidence. Most species are under 10 centimeters long, with a body divided into an unsegmented, bulbous trunk and a narrower front section called the introvert, which can retract into the trunk and bears the mouth at its tip, typically ringed by short tentacles. Most sipunculans burrow in sandy or muddy shallow-water sediment and feed by extending the introvert to gather food particles.