The Sipuncula or Sipunculida (common names sipunculid worms or peanut worms) is a class containing about 162 species of unsegmented marine annelid worms. Sipuncula was once considered a phylum , but was demoted to a class of Annelida, based on recent molecular work.

New records and five new species of sipunculans (Sipuncula) from the central and northwestern Mexican Pacific. European Journal of Taxonomy. 925: 179-219., available online at https://europeanjournaloftaxonomy.eu/index.php/ejt/article/view/2463 note: Review of Sipuncula for the Mexican Pacific (see Table 1 for list)

Sipuncula or Sipunculida is a phylum of bilaterally symmetrical, unsegmented marine invertebrates, characterized by a worm-like body divided into a trunk and retractable introvert, typically with tentacles on the tip of the introvert.

Peanut worm, any member of the invertebrate phylum Sipuncula, a group of unsegmented marine worms. The head bears a retractable “introvert” with the mouth at its end. The mouth is usually surrounded by one or more rings of tentacles.

2025年2月5日 · New records and five new species of sipunculans (Sipuncula) from the central and northwestern Mexican Pacific. <em>European Journal of Taxonomy.</em> 925: 179-219., available online at https://europeanjournaloftaxonomy.eu/index.php/ejt/article/view/2463

Sipunculus is a genus of worms belonging to the family Sipunculidae. [1] Sipunculus is a variant spelling of the Latin siphunculus ("little tube"), [2] a diminutive of sipho from Greek σίφων (síphōn, " tube, pipe "). Siphunculus was used for fossilized worm-shaped organisms like Siphunculus scaber by the Welsh naturalist Edward Lhuyd in 1699. [3] .

General Sipunculan Anatomy -- The body is completely unsegmented, and the intestine forms a twisted loop, with the anus on the side of the body. Typical of sipunculans is a forward (anterior) body section, the introvert, which can be retracted into the body by the retractor muscles.