Spionida is a suborder

Order (biology)

In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 of marine polychaete

Polychaete

The Polychaeta or polychaetes are a class of annelid worms, generally marine. Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. Indeed, polychaetes are sometimes referred to as bristle worms. More than 10,000...

 worms in the order Canalipalpata

Canalipalpata

Canalipalpata, also known as bristle-footed annelids or fan-head worms, is an order of polychaete worms, with 31 families in it including the Sabellida and the Alvinellidae, a family of deep-sea worms associated with hydrothermal vents.The Canalipalpata have no teeth or jaws. Most are filter feeders...

. Spionids are cosmopolitan and live in soft substrates in the littoral or neritic zone

Neritic zone

The neritic zone, also called coastal waters, the coastal ocean or the sublittoral zone, is the part of the ocean extending from the low tide mark to the edge of the continental shelf, with a relatively shallow depth extending to about 200 meters...

s.

Characteristics

Spionids have a single pair of flexible feeding tentacle

Tentacle

A tentacle or bothrium is one of usually two or more elongated flexible organs present in animals, especially invertebrates. The term may also refer to the hairs of the leaves of some insectivorous plants. Usually, tentacles are used for feeding, feeling and grasping. Anatomically, they work like...

s with grooves, arising directly from the prostomium

Prostomium

Prostomium is the first body segment in annelid worms. It is in front of the mouth, being usually a small shelf- or lip-like extension over the dorsal side of the mouth. It sometimes bears antennae and eyes. It often functions like a kind of overlip when the animal is feeding...

. The mouth has no jaws and the pharynx is partly eversible. Some species have small eye spots and some a central sensory lobe. Some of the anterior segments paired gills. The parapodia

Parapodium

Parapodia , singular parapodium, are paired, un-jointed lateral outgrowths from the bodies of two different invertebrate groups, which are primarily marine in habitat...

 or lateral lobes have large lamellae. The chaeta

Chaeta

A chaeta or cheta is a chitinous bristle or seta found on an insect, arthropod or annelid worms such as the earthworm, although the term is also frequently used to describe similar structures in other invertebrates. The plural form is chaetae or chetae.In the Polychaeta, they are located on the...

e are unbranched capillaries, spines and hooks.

Families

• Aberrantidae
• Apistobranchidae Mesnil and Caullery, 1898
• Chaetopteridae Audouin and Milne-Edwards, 1833
• Heterospionidae
• Longosomatidae Hartman, 1944
• Magelonidae
• Poecilochaetidae Hannerz, 1956
• Spionidae
  Spionidae
  Spionidae is a family within the Polychaeta. Spionids are selective deposit feeders that use their two grooved palps to locate prey but some spionids are capable of interface feeding i.e. switching between deposit and suspension feeding. Spionids produce tubes by cementing sand grains and detritus...
  
  Grube, 1850
• Trochochaetidae Pettibone, 1963
• Uncispionidae Green, 1982