The Echiura, or spoon worms, are a small group of marine animals. Once treated as a separate phylum, they are now considered to belong to Annelida. Annelids typically have their bodies divided into segments, but echiurans have secondarily lost their segmentation. The majority of echiurans live in burrows in soft sediment in shallow water, but some live in rock crevices or under boulders, and there are also deep sea forms. More than 230 species have been described. Spoon worms are cylindrical, soft-bodied animals usually possessing a non-retractable proboscis which can be rolled into a scoop-shape to feed. In some species the proboscis is ribbon-like, longer than the trunk and may have a forked tip. Spoon worms vary in size from less than a centimetre in length to more than a metre.
Heteroconchia is a taxonomic infraclass of diverse bivalve molluscs, belonging to the subclass Autobranchia.
Urechis unicinctus, known as the fat innkeeper worm or penis fish, is a species of marine spoon worm in East Asia. It is found in Bohai Gulf of China and off the Korean and Hokkaido coasts. It is not to be confused with a closely related species, Urechis caupo, which occurs on the western coast of North America and shares common names. The body is about 10–30 cm long, cylindrical in shape and yellowish-brown in color. On the surface of the body there are many small papillae.
The Vermetidae, the worm snails or worm shells, are a taxonomic family of small to medium-sized sea snails, marine gastropod molluscs in the clade Littorinimorpha. The shells of species in the family Vermetidae are extremely irregular, and do not resemble the average snail shell, hence the common name "worm shells" or "worm snails".
Carditidae is a family of marine bivalve clams of the order Carditida, which was long included in the Venerida. They are the type taxon of the superfamily Carditoidea.
Bonelliidae is a family of marine worms 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.
Metabonellia is a genus of marine spoon worms in the family Bonelliidae. It is a monotypic genus and Metabonellia haswelli is the only species. It is commonly known as the green spoon worm and is found in shallow waters around Australia.
Urechidae is a family of spoonworms in the subclass Echiura. The only genus in the family is Urechis, which has four species.
Ochetostoma erythrogrammon is a species of spoon worm in the family Thalassematidae. It is found in shallow water in the Atlantic Ocean, the Mediterranean Sea, and the Indian and Pacific Oceans, burrowing in soft sediment.
Thalassematidae is a family of spoonworms in the suborder Echiurida.
Echiuridae is a family of spoon worms in the suborder Echiurida. It is a monotypic family, the only genus being Echiurus. These worms burrow into soft sediment on the seabed.
Ikeda taenioides is a species of spoon worm in the family Ikedidae. It is native to the northern Pacific Ocean where it is found in the subtidal waters around Japan.
Anelassorhynchus is a genus of spoonworms in the subclass Echiura.
Maxmuelleria lankesteri is a species of spoon worm in the family Bonelliidae. It is found in the North Atlantic Ocean. It burrows into soft sediment on the seabed, mostly in deep water.
Heteropsammia is a genus of apozooxanthellate corals that belong to the family Dendrophylliidae.
Leocratides kimuraorum is a species of marine worm belonging to Hesionidae, which is known for the intensity of its intraspecific fighting. Its body is nearly translucent and up to 29 millimetres (1.1 in) long.
Leocratides is a genus of marine hesionid polychaete worms dwelling in hexactinellid sponges.
Echiurida is a suborder of the order Echiuroidea, an order of polychaete worms.
Thalassema is a genus of spoonworms in the subclass Echiura.
Bonelliida is a suborder of the order Echiuroidea, an order of polychaete worms.
