The Saccocirridae are small interstitial

polychaete Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are ...

s common in coarse sand on reflective, surf beaches, usually within the zone of retention. The Saccociridae are members of the clade Protodrilida, which is in turn part of the clade Canalipalpata. Saccocirridae have a worldwide distribution and many more species likely remain to be described. These polychates are usually between 2 and 10 mm in length and 500 μm wide. They have reduced parapodia and are considered a true interstitial species, incapable of burrowing through finer

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sa ...

Morphology

Based on ''Saccocirrus sonomacus'' from the Pacific Coast of the Americas, the prostomium supports a pair of grooved palps that have a primarily sensory purpose. A pair of eyes are also present. The peristomium is probably reduced to a circumoral ring. The pygidium is usually bilobed.

References

Polychaetes Annelid families {{annelid-stub