Temporal range: Lower Cambrian to Recent
About 20% of the known species are benthic and can attach to algae or rocks. They are found in all marine waters from surface tropical waters and shallow tide pools to the deep sea and polar regions. Most chaetognaths are transparent and are torpedo shaped, but some deep-sea species are orange. They range in size from 2 to 120 millimetres (0.079 to 4.724 in).
These animals are usually considered a type of protostome.
- meaning hair-jaws
- Bone Q.; et al. (1991). The biology of chaetognaths. London: Oxford University Press.
- Thuesen, E.V.; et al. (1991), "The tetrodotoxin venom of chaetognaths", in Bone, Q. (ed.), The biology of chaetognaths, London: Oxford University Press, pp. 55–60
- Chen J.-Y., and D.-Y. Huang. 2002. A possible Lower Cambrian chaetognath (arrow worm). Science 298:187.
- Hu S.-X. 2005. Taphonomy and palaeoecology of the Early Cambrian Chengjiang Biota from Eastern Yunnan, China. Berliner Paläobiologische Abhandlungen 7:1–197.
- Szaniawski H. 2005. Cambrian chaetognaths recognized in Burgess Shale fossils. Acta Palaeontologica Polonica 50:1-8.