Echiura

Echiura
Temporal range: Darriwilian–Recent[1]
Urechis caupo
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Annelida
Clade: Pleistoannelida
Clade: Sedentaria
Subclass: Echiura
Newby, 1940[2][3]
Subdivision
Echiurus

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.[4] 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.

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 Middle Ordovician.

  1. ^ Botting, Joseph; Muir, Lucy (2023). "Echiuran worms from the Middle Ordovician Castle Bank Biota of Wales, UK" (PDF). Acta Palaeontologica Polonica. 68. doi:10.4202/app.01107.2023.
  2. ^ Cite error: The named reference EncycloBrit was invoked but never defined (see the help page).
  3. ^ Tanaka, Masaatsu (2017). "Echiura". WoRMS. World Register of Marine Species. Retrieved 17 February 2019.
  4. ^ Zhang, Z.-Q. (2011). "Animal biodiversity: An introduction to higher-level classification and taxonomic richness" (PDF). Zootaxa. 3148: 7–12. doi:10.11646/zootaxa.3148.1.3. Archived (PDF) from the original on 2022-10-09.