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Temporal range: Upper Carboniferous – Recent
|Bonellia viridis, female|
The Echiura, or spoon worms, are a small group of marine animals. They are often considered to be a group of annelids, although they lack the segmented structure found in other members of that group, and so may also be treated as a separate phylum.
- Struck, TH et al. (2007-05-27). "Annelid phylogeny and the status of Sipuncula and Echiura". BMC Evolutionary Biology (BioMed Central) 7: 57. doi:10.1186/1471-2148-7-57. PMC 1855331. PMID 17411434. http://www.biomedcentral.com/1471-2148/7/57/abstract