Echiura
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.
| Echiura Temporal range: | |
|---|---|
| Urechis caupo | |
| Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Annelida |
| Class: | Polychaeta |
| Subclass: | Echiura Newby, 1940 |
| Subdivision | |
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Most are deposit feeders, collecting detritus from the sea floor. Fossils of these worms are seldom found and the earliest known fossil specimen is from the Upper Carboniferous (Pennsylvanian).