Temporal range: Upper Early Cambrian–Silurian
Conway Morris & Robinson, 1986
|Families and genera
(sensu Harvey et al. 2010)
The palaeoscolecids are a group of ecdysozoan worms resembling armoured priapulids. They are known from the Lower Cambrian to the late Silurian; they are mainly found as disarticulated sclerites, but are also preserved in many of the Cambrian lagerstätten. They take their name from the typifying genus Palaeoscolex.
Palaeoscolecids bear an annulated trunk ornamented with circular patterns of phosphatic tesselating plates; a layered cuticle; and an armoured proboscis. They are usually a few centimetres in length. There is no one character that unites the palaeoscolecids as a clade (indeed they are likely paraphyletic), and few individual specimens contain all characteristic palaeosolecid traits.
They are considered to belong to the cycloneuralia, although their position within this group is unresolved; they may lie with the priapulids or nematomorpha. They have also been described as a sister-group to the ecdysozoa, although as more characters are described a position closer to the priapulids becomes most probable. A nematomorph affinity appears to be an artefact that results from under-sampling of the priapulid stem group.
Other genera include Cricocosmia from the Lower Cambrian Chengjiang biota. Their relationship with the archaeopriapulida is also unclear; it could be that both groups are a paraphyletic assemblage containing the priapulids.
In addition to the genera listed in the taxobox, other worms are commonly referred to the palaeoscolecids, even though they lack the cuticular structure that defines the group. These include Louisella, Maotianshania, Cricocosmia, Tabelliscolex, Tylotites and others. It's also possible that Markuelia represents an embryonic Palaeoscolecid.
- Wills, M. A. (1 April 1998). "Cambrian and Recent Disparity: the Picture from Priapulids". Paleobiology 24 (2): 155–286. doi:10.2307/2401237 (inactive 2014-06-06). JSTOR 2401237.
- Harvey, T. H.; Dong, X.; Donoghue, P. C. (2010). "Are palaeoscolecids ancestral ecdysozoans?". Evolution & Development 12 (2): 177–200. doi:10.1111/j.1525-142X.2010.00403.x. PMID 20433458.
- Andrey Y. Ivantsov & Ryszard Wrona (2004). "Articulated palaeoscolecid sclerite arrays from the Lower Cambrian of eastern Siberia" (PDF). Acta Geologica Polonica 54 (1): 1–22.
- Xianguang Hou, Richard Aldridge, Jan Bergström, David Siveter, Derek Siveter (2004). The Cambrian fossils of Chengjiang, China: the flowering of early animal life. Wiley-Blackwell. p. 233. ISBN 978-1-4051-0673-3.
- Zhu, M.; Babcock, L.; Steiner, M. (2005). "Fossilization modes in the Chengjiang Lagerstätte (Cambrian of China): testing the roles of organic preservation and diagenetic alteration in exceptional preservation". Palaeogeography Palaeoclimatology Palaeoecology 220: 31–37. doi:10.1016/j.palaeo.2003.03.001.
- Conway Morris, S.; Peel, J. S. (2010). "New palaeoscolecidan worms from the Lower Cambrian: Sirius Passet, Latham Shale, and Kinzers Shale". Acta Palaeontologica Polonica 55 (1): 141–156. doi:10.4202/app.2009.0058.
- http://www.ucl.ac.uk/EarthSci/Grzybowski/publications/GFSP15.pdf#page=82. Missing or empty
- Peel, J. S. (2010). "A Corset-Like Fossil from the Cambrian Sirius Passet Lagerstätte of North Greenland and Its Implications for Cycloneuralian Evolution". Journal of Paleontology 84 (2): 332–340. doi:10.1666/09-102R.1.
- Jian Han, Jianni Liu, Zhifei Zhang, Xinglian Zhang & Degan Shu (2007). "Trunk ornament on the palaeoscolecid worms Cricocosmia and Tabelliscolex from the Early Cambrian Chengjiang deposits of China". Acta Palaeontologica Polonica 52 (2): 423–431.
- Duan, B.; Dong, X. -P.; Donoghue, P. C. J. (2012). "New palaeoscolecid worms from the Furongian (upper Cambrian) of Hunan, South China: Is Markuelia an embryonic palaeoscolecid?". Palaeontology 55 (3): 613. doi:10.1111/j.1475-4983.2012.01148.x.