Oweniidae is a family of segmented worms in the phylum Annelida and class Polychaeta. They are soft-bodied little worms without a hard skeleton. The body is a muscular cylinder arranged in segments with a fluid-filled cavity. The segments help them when moving.
There are eighteen species of Owenids in the family Oweniidae, and they can be found worldwide in relatively clean sand. Individual species vary in size but are generally three millimetres wide and five centimetres long.
Owenids live in small tubes that they construct in the sand. The flexible, long tubes are built from sand or fragments of shell. Sand and shell fragments are laid on top of each other much like roof tiles.
The tubes are longer than the worms, with the tubes ending in a short crown used to feed. They feed on organic matter, such as smaller organisms or their remains in the mud where they live. They are filter feeders and grazers.
Reproduction occurs in the water, where the eggs and sperm are released. Mitraria is a tiny, transparent creature develop from the larva. It appears different to its adult form as it grows and sheds much of its larval structure before becoming an adult worm.