Chordate

Chordates; Temporal range: Ediacaran–Present, 555–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N (Possible Ediacaran record, 555 Ma)
Scientific classification
Kingdom:	Animalia
Subkingdom:	Eumetazoa
Clade:	ParaHoxozoa
Clade:	Bilateria
Clade:	Nephrozoa
Superphylum:	Deuterostomia
Phylum:	Chordata; Haeckel, 1874
Subgroups
	†Vetulocystidae?; †Vetulicolia? (Paraphyletic?); †Yunnanozoon?; †Cathaymyrus; †Pikaia; Cephalochordata; Olfactores Tunicata; Total group Vertebrata/Craniata †Emmonsaspis; †Metaspriggina; †Nuucichthys; †Myllokunmingiidae; †Conodonta?; Vertebrata; ; ; And see text

Chordates, phylum Chordata, are a phylum of animals which have a notochord. The group includes vertebrates, with some closely related invertebrates.

Classification

Taxonomy

Phylum Chordata
- Tunicata – (tunicates, formerly Urochordata; 3,000 species)
- †Vetulicolia (8 Cambrian species of fossil)
- Cephalochordata – (lancelets, 30 species)
- Vertebrata (vertebrates – animals with backbones; 57,739 species)
  - Agnatha (jawless vertebrates; 100+ species)
    - Myxini or Hyperotreti (hagfish; 65 species)
    - Conodonta (Conodonts)
    - Hyperoartia (Lampreys)
    - †Cephalaspidomorphi (Paleozoic jawless fish)
    - †Pteraspidomorphi (Paleozoic jawless fish)
  - Gnathostomata (jawed vertebrates)
    - †Placodermi (Paleozoic armoured forms)
    - Chondrichthyes (cartilaginous fish; 300+ species)
    - †Acanthodii (Paleozoic "spiny sharks")
    - Osteichthyes (bony fishes; 30,000+ species)
      - Actinopterygii (ray-finned fish; about 30,000 species)
      - Sarcopterygii (lobe-finned fish)
    - Tetrapoda (four-legged vertebrates; 18,000+ species)

Phylogeny

Chordata

Tunicata

	Appendicularia (formerly Larvacea)

	Thaliacea

	Ascidiacea

Cephalochordata

Craniata

Myxini

Vertebrata

Conodonta†

Cephalaspidomorphi†

Hyperoartia

Pteraspidomorphi†

Gnathostomata

Placodermi†

Chondrichthyes

Teleostomi

Acanthodii†

Osteichthyes

Actinopterygii

Sarcopterygii

void

Tetrapoda

Amphibia

Amniota

Synapsida

void

	Mammalia

Sauropsida

void

	Aves

Note: Lines show likely evolutionary relationships. Extinct groups are marked with a "†". Extinct animals are ones that have completely died out.

Origin of chordates

According to a long-standing theory, the origin of chordates may be found in transformed larvae of sea-squirts (tunicates). Adult tunicates are sessile, but their larvae are motile, and have some features found in early vertebrates. The process of paedomorphosis, where juvenile features are retained in the adult, is the proposed mechanism. Genome analysis shows that tunicates are the closest living relatives of vertebrates.

References

↑ Yang, Chuan; Li, Xian-Hua; Zhu, Maoyan; Condon, Daniel J.; Chen, Junyuan (2018). "Geochronological constraint on the Cambrian Chengjiang biota, South China" (PDF). Journal of the Geological Society. 175 (4): 659–666. Bibcode:2018JGSoc.175..659Y. doi:10.1144/jgs2017-103. ISSN 0016-7649. S2CID 135091168. Archived (PDF) from the original on 2022-10-09.
↑ Fedonkin, M. A.; Vickers-Rich, P.; Swalla, B. J.; Trusler, P.; Hall, M. (2012). "A new metazoan from the Vendian of the White Sea, Russia, with possible affinities to the ascidians". Paleontological Journal. 46 (1): 1–11. Bibcode:2012PalJ...46....1F. doi:10.1134/S0031030112010042. S2CID 128415270.
↑ Haeckel, E. (1874). Anthropogenie oder Entwicklungsgeschichte des Menschen. Leipzig: Engelmann.
↑ Nielsen, C. (July 2012). "The authorship of higher chordate taxa". Zoologica Scripta. 41 (4): 435–436. doi:10.1111/j.1463-6409.2012.00536.x. S2CID 83266247.
1 2 He, K.; Liu, J.; Han, J.; Ou, Q.; Chen, A.; Zhang, Z.; Fu, D.; Hua, H.; Zhang, X.; Shu, D. (2023). "Comment on "Ultrastructure reveals ancestral vertebrate pharyngeal skeleton in yunnanozoans"". Science. 381 (6656) eade9707. doi:10.1126/science.ade9707. PMID 37499008.
↑ Mussini, G.; Smith, M. P.; Vinther, J.; Rahman, I. A.; Murdock, D. J. E.; Harper, D. A. T.; Dunn, F. S. (2024). "A new interpretation of Pikaia reveals the origins of the chordate body plan". Current Biology. 34 (13): 2980–2989.e2. Bibcode:2024CBio...34.2980M. doi:10.1016/j.cub.2024.05.026. PMID 38866005.
1 2 Lerosey-Aubril, R.; Ortega-Hernández, J. (2024). "A long-headed Cambrian soft-bodied vertebrate from the American Great Basin region". Royal Society Open Science. 11 (7) 240350. Bibcode:2024RSOS...1140350L. doi:10.1098/rsos.240350. PMC 11267725. PMID 39050723.
↑ Garstang, Walter 1894. Preliminary notes on a new theory of the phylogeny of the chordates. Zoologischer Anzeiger 17, p122.
↑ Garstang, Walter 1928. The morphology of the tunicata, and its bearing on the phylogeny of the Chordata. Quarterly Journal of Microscopical Science 72, p51.
↑ de Beer, Gavin 1951. Embryos and ancestors. 3rd ed, Oxfor, The evolution of chordates, p76.
↑ Delsuc, Frédéric et al. 2006. Tunicates and not cephalochordates are the closest living relatives of vertebrates. Nature 439, 965-968

Other websites

Chordate node at Tree Of Life Archived 2007-02-24 at the Wayback Machine
Chordate node at NCBI Taxonomy

[1] Yang, Chuan; Li, Xian-Hua; Zhu, Maoyan; Condon, Daniel J.; Chen, Junyuan (2018). "Geochronological constraint on the Cambrian Chengjiang biota, South China" (PDF). Journal of the Geological Society. 175 (4): 659–666. Bibcode:2018JGSoc.175..659Y. doi:10.1144/jgs2017-103. ISSN 0016-7649. S2CID 135091168. Archived (PDF) from the original on 2022-10-09.

[2] Fedonkin, M. A.; Vickers-Rich, P.; Swalla, B. J.; Trusler, P.; Hall, M. (2012). "A new metazoan from the Vendian of the White Sea, Russia, with possible affinities to the ascidians". Paleontological Journal. 46 (1): 1–11. Bibcode:2012PalJ...46....1F. doi:10.1134/S0031030112010042. S2CID 128415270.

[3] Haeckel, E. (1874). Anthropogenie oder Entwicklungsgeschichte des Menschen. Leipzig: Engelmann.

[Nielsen2012-4] Nielsen, C. (July 2012). "The authorship of higher chordate taxa". Zoologica Scripta. 41 (4): 435–436. doi:10.1111/j.1463-6409.2012.00536.x. S2CID 83266247.

[He2023-5] 1 2 He, K.; Liu, J.; Han, J.; Ou, Q.; Chen, A.; Zhang, Z.; Fu, D.; Hua, H.; Zhang, X.; Shu, D. (2023). "Comment on "Ultrastructure reveals ancestral vertebrate pharyngeal skeleton in yunnanozoans"". Science. 381 (6656) eade9707. doi:10.1126/science.ade9707. PMID 37499008.

[Mussini2024-6] Mussini, G.; Smith, M. P.; Vinther, J.; Rahman, I. A.; Murdock, D. J. E.; Harper, D. A. T.; Dunn, F. S. (2024). "A new interpretation of Pikaia reveals the origins of the chordate body plan". Current Biology. 34 (13): 2980–2989.e2. Bibcode:2024CBio...34.2980M. doi:10.1016/j.cub.2024.05.026. PMID 38866005.

[Lerosey-Aubril2024-7] 1 2 Lerosey-Aubril, R.; Ortega-Hernández, J. (2024). "A long-headed Cambrian soft-bodied vertebrate from the American Great Basin region". Royal Society Open Science. 11 (7) 240350. Bibcode:2024RSOS...1140350L. doi:10.1098/rsos.240350. PMC 11267725. PMID 39050723.

[8] Garstang, Walter 1894. Preliminary notes on a new theory of the phylogeny of the chordates. Zoologischer Anzeiger 17, p122.

[9] Garstang, Walter 1928. The morphology of the tunicata, and its bearing on the phylogeny of the Chordata. Quarterly Journal of Microscopical Science 72, p51.

[10] Beer, Gavin 1951. Embryos and ancestors. 3rd ed, Oxfor, The evolution of chordates, p76.

[11] Delsuc, Frédéric et al. 2006. Tunicates and not cephalochordates are the closest living relatives of vertebrates. Nature 439, 965-968