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Ottoia prolifica from the Walcott Quarry of the Burgess Shale (Middle Cambrian) near Field, British Columbia, Canada.
Scientific classification e
Kingdom: Animalia
Clade: Cycloneuralia
Clade: Scalidophora


Scalidophora is a group of marine pseudocoelomate protostomes, consisting of the three phyla Kinorhyncha, Priapulida, and Loricifera.[2] The three phyla have four characters in common — chitinous cuticle that is moulted, rings of scalids on the introvert, flosculi, and two rings of introvert retracts.[3] Their closest relatives are thought to be the Panarthropoda, Nematoda and Nematomorpha; they are thus placed in the group Ecdysozoa.

The two species in the genus Markuelia, known from fossilized embryos from the middle Cambrian, are thought to be stem Scalidophorans.

The group has also been considered a single group, Cephalorhyncha,[4] with three classes.

The group is named after the spines (scalids) covering the introvert (head that can be retracted into the trunk).[5]


  1. ^ Harvey, T. H.; Dong, X.; Donoghue, P. C. (March–April 2010). "Are palaeoscolecids ancestral ecdysozoans?". Evolution & Development. 12 (2): 177–200. doi:10.1111/j.1525-142X.2010.00403.x. PMID 20433458. 
  2. ^ Telford, M. J.; Bourlat, S. J.; Economou, A.; Papillon, D.; Rota-Stabelli, O. (27 April 2008). "The evolution of the Ecdysozoa" (pdf). Philosophical Transactions of the Royal Society B. 363 (1496): 1529–1537. doi:10.1098/rstb.2007.2243. PMC 2614232Freely accessible. PMID 18192181. 
  3. ^ Heiner, I., Kristensen, R.H. 2005. Two new species of the genus Pliciloricus (Loricifera, Pliciloricidae) from the Faroe Bank, North Atlantic. Zoologischer Anzeiger. 243: 121–138.
  4. ^ Dirnberger, J. "Explanations and Difficulties in Invertebrate Phylogeny". Invertebrate Zoology. Kennesaw State University. Retrieved 2012-08-11. 
  5. ^ Dunn, C. W.; Hejnol, A.; Matus, D. Q.; Pang, K.; Browne, W. E.; Smith, S. A.; Seaver, E.; Rouse, G. W.; Obst, M.; et al. (10 April 2008). "Broad Phylogenomic Sampling Improves Resolution of the Animal Tree of Life". Nature. 452 (7188): 745–749. doi:10.1038/nature06614. PMID 18322464.