Syllidae

thumb|Schizogamy in syllid polychaete Syllidae, commonly known as the necklace worms, is a family of small to medium-sized polychaete worms. Syllids are distinguished from other polychaetes by the presence of a muscular region of the anterior digestive tract known as the proventricle.

Syllid worms range in size from to . Most syllids are benthic organisms that transition to a pelagic epitoke for reproduction. They are found in all regions of the ocean, from the intertidal zone to the deep sea, and are especially abundant in shallow water.