Scalidophora

"Cephalorhyncha" redirects here. For the kinorhynch genus, see Cephalorhyncha (genus).

Scalidophora
Ottoia prolifica from the Walcott Quarry of the Burgess Shale (Middle Cambrian) near Field, British Columbia, Canada.
Scientific classification Edit this classification
Kingdom: Animalia
Subkingdom: Eumetazoa
Clade: ParaHoxozoa
Clade: Bilateria
Clade: Nephrozoa
Clade: Protostomia
Superphylum: Ecdysozoa
Clade: Scalidophora
Lemburg, 1995
Phyla
Synonyms
  • Cephalorhyncha sensu Nielsen, 1995
  • Priapozoa

Scalidophora is a group of marine pseudocoelomate ecdysozoans that was proposed on morphological grounds to unite three phyla: the Kinorhyncha, the Priapulida and the Loricifera.[8][9] 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.[10] The introvert and abdomen are separated by a distinct neck region in all groups, but in adult macroscopic priapulids it becomes rudimentary in Priapulus and is completely absent in Halicryptus.[11] However, the monophyly of the Scalidophora was not supported by several molecular studies, where the position of the Loricifera was uncertain[8], closely related to Nematoida and Panarthropoda,[9] or as the sister group to Nematoda.[12] A 2022 study by Howard and co-authors recovered a monophyletic Scalidophora, but suggested that non-monophyly of Scalidophora should not be ruled out.[13]

The genus Markuelia, known from fossilized embryos from the middle Cambrian, is thought to be a stem scalidophoran.

The group is named after the spines (scalids) covering the introvert (head that can be retracted into the trunk).[14]

A similar group Cephalorhyncha (meaning "beak"-head)[15] was proposed by Malakhov in 1980 as a phylum consisting of Priapulida, Kinorhyncha, and Nematomorpha, with Lorificera being added later.[16] Nielsen recognised Priapulida, Kinorhyncha and Loricifera as a monophyletic group and in 1995 chose to use the name Cephalorhyncha for a group uniting the three phyla, excluding the Nematomorpha.[17]

References

  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. S2CID 16872271.
  2. ^ Maas, A.; Waloszek, D.; Haug, J.T.; Müller, K.J. (2007). "A possible larval roundworm from the Cambrian 'Orsten' and its bearing on the phylogeny of Cycloneuralia". Memoirs of the Association of Australasian Palaeontologists. 34: 499–519. Retrieved 5 May 2026.
  3. ^ Dong, X. -P.; Bengtson, S.; Gostling, N. J.; Cunningham, J. A.; Harvey, T. H. P.; Kouchinsky, A.; Val'Kov, A. K.; Repetski, J. E.; Stampanoni, M.; Marone, F.; Donoghue, P. C. J. (2010). "The anatomy, taphonomy, taxonomy and systematic affinity of Markuelia: Early Cambrian to Early Ordovician scalidophorans" (PDF). Palaeontology. 53 (6): 1291–1314. Bibcode:2010Palgy..53.1291D. doi:10.1111/j.1475-4983.2010.01006.x. S2CID 53483146.
  4. ^ a b Liu, Yunhuan; Qin, Jiachen; Wang, Qi; Maas, Andreas; Duan, Baichuan; Zhang, Yanan; Zhang, Hu; Shao, Tiequan; Zhang, Huaqiao (May 2019). "New armoured scalidophorans (Ecdysozoa, Cycloneuralia) from the Cambrian Fortunian Zhangjiagou Lagerstätte, South China". Papers in Palaeontology. 5 (2): 241–260. Bibcode:2019PPal....5..241L. doi:10.1002/spp2.1239.
  5. ^ Zhang, Hua-Qiao (September 2022). "The evolutionary relationships of the earliest known cycloneuralians and a new record from the Cambrian Fortunian of South China". Palaeoworld. 31 (3): 389–401. doi:10.1016/j.palwor.2021.09.003.
  6. ^ Shao, T.Q.; Qin, J.C.; Shao, Y.; Liu, Y.H.; Waloszek, D.; Maas, A.; Duan, B.C.; Wang, Q.; Xu, Y.; Zhang, H.Q. (October 2020). "New macrobenthic cycloneuralians from the Fortunian (lowermost Cambrian) of South China". Precambrian Research. 349 105413. Bibcode:2020PreR..34905413S. doi:10.1016/j.precamres.2019.105413.
  7. ^ Shao, T.Q.; Wang, Q.; Liu, Y.H.; Qin, J.C.; Zhang, Y.N.; Liu, M.J.; Shao, Y.; Zhao, J.Y.; Zhang, H.Q. (October 2020). "A new scalidophoran animal from the Cambrian Fortunian Stage of South China and its implications for the origin and early evolution of Kinorhyncha". Precambrian Research. 349 105616. Bibcode:2020PreR..34905616S. doi:10.1016/j.precamres.2020.105616.
  8. ^ a b Telford, M. J.; Bourlat, S. J.; Economou, A.; Papillon, D.; Rota-Stabelli, O. (27 April 2008). "The evolution of the Ecdysozoa". Philosophical Transactions of the Royal Society B. 363 (1496): 1529–1537. doi:10.1098/rstb.2007.2243. PMC 2614232. PMID 18192181.
  9. ^ a b Yamasaki, Hiroshi; Fujimoto, Shinta; Miyazaki, Katsumi (2015-06-30). "Phylogenetic position of Loricifera inferred from nearly complete 18S and 28S rRNA gene sequences". Zoological Letters. 1: 18. doi:10.1186/s40851-015-0017-0. ISSN 2056-306X. PMC 4657359. PMID 26605063.
  10. ^ 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.
  11. ^ Multicellular Animals: Volume III: Order in Nature - System Made by Man, Volum 3
  12. ^ Laumer, Christopher E.; Fernández, Rosa; Lemer, Sarah; Combosch, David; Kocot, Kevin M.; Riesgo, Ana; Andrade, Sónia C. S.; Sterrer, Wolfgang; Sørensen, Martin V.; Giribet, Gonzalo (2019-07-10). "Revisiting metazoan phylogeny with genomic sampling of all phyla". Proceedings of the Royal Society B: Biological Sciences. 286 (1906) 20190831. doi:10.1098/rspb.2019.0831. ISSN 0962-8452. PMC 6650721. PMID 31288696.
  13. ^ Howard, Richard J.; Giacomelli, Mattia; Lozano-Fernandez, Jesus; Edgecombe, Gregory D.; Fleming, James F.; Kristensen, Reinhardt M.; et al. (10 March 2022). "The Ediacaran origin of Ecdysozoa: Integrating fossil and phylogenomic data". Journal of the Geological Society. 179 (4). Bibcode:2022JGSoc.179..107H. doi:10.1144/jgs2021-107. hdl:2445/186596. ISSN 0016-7649. S2CID 246494357.
  14. ^ 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. Bibcode:2008Natur.452..745D. doi:10.1038/nature06614. PMID 18322464. S2CID 4397099.
  15. ^ Dirnberger, J. "Explanations and Difficulties in Invertebrate Phylogeny". Invertebrate Zoology. Kennesaw State University. Archived from the original on 2013-02-07. Retrieved 2012-08-11.
  16. ^ Nielsen, Claus (2012). Animal Evolution: Interrelationships of the living phyla (3rd ed.). Oxford University Press. ISBN 978-0-19-960603-0.
  17. ^ Nielsen, Claus (1995). Animal Evolution: Interrelationships of the living phyla. Oxford University Press. ISBN 978-0-19-850682-9.


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