Polychaeta

paraphyletic group of annelids Polychaeta (Polychaeta) is a class of organisms united by key anatomical and physiological traits. It contains 5 orders with 51 known species. This includes the order groups Amphinomida, Echiuroidea, Eunicida, Phyllodocida, and Sabellida. Among its members, 1 species are currently classified as threatened (Critically Endangered, Endangered, or Vulnerable). It belongs to Segmented Worms (Annelida).