Bonelliidae

Bonelliidae is a family of marine worms (Subclass Echiura, of the class Polychaeta, in the phylum Annelida) noted for being sexually dimorphic, with males being tiny in comparison with the females. They occupy burrows in the seabed in many parts of the world's oceans, often at great depths.

==Characteristics== Members of the class Echiura are plump, unsegmented worms, commonly known as spoonworms. The mouth is at the anterior end of the trunk and a flattened proboscis extends forward in front of the mouth. The ventral side of the proboscis has a ciliated channel along which food particles and mucus are moved towards the mouth. Close behind the mouth are two hooked chaetae and one or two nephridial pores. The gut is much longer than the body and is folded and coiled inside the coelom (body cavity). The anus is at the posterior end of the body and two anal vesicles with ciliated funnels open into the cloaca.