Quentin Bone, Marine Biological Association Laboratory, Plymouth, UK
Published online: April 2001
DOI: 10.1038/npg.els.0001528
The Chordata are a group of animals characterized by a dorsal tubular nerve cord, a notochord and gill slits. The group includes the Vertebrata (Craniata), Tunicata, Acrania and Conodonta.
Keywords: vertebrates; conodonts; acraniates; gnathostomes; tunicata; origins; phylogeny
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Figure 1. Ranking of the groups comprising the Chordata.
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Figure 2. Comparison of gene expression in brain regions of amphioxus (acraniate), mouse (craniate) and ascidian tadpole larva (tunicate). The assumption is that the regions indicated in amphioxus and the tunicate tadpole larva are homologous to the vertebrate brain regions labelled in the mouse, based on the early developmental expression of the gene family members on the right. Note that an amphioxus member of the Pax-2/5/8 family has not yet been identified. From Williams and Holland (1998) Molecular evolution of the brain. Brain Behaviour and Evolution 52: 177–185 with permission.
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Figure 3. Schematic view of the relationships between chordates, based partly upon molecular data.
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| Further Reading | |
| Aldridge RJ, Briggs DEG, Smith MP, Clarkson ENK and Clark NDL (1993) The anatomy of conodonts. Philosophical Transactions of the Royal Society London, B 340: 405–421. | |
| book Bone Q (ed.) (1998) Biology of Pelagic Tunicates. Oxford: Oxford University Press. | |
| book Bone Q, Marshall NB and Blaxter JHS (1995) Biology of Fishes, 2nd edn. London: Blackie Academic & Professional. | |
| Garstang W (1928) The morphology of the Tunicata and its bearing on the phylogeny of the Chordata. Quarterly Journal of Microscopical Science 72: 51–187. | |
| Holland PWH (1996) Molecular biology of lancelets: insights into development and evolution. Israel Journal of Zoology 42: 247–272. | |
| Lacalli TC (1996) Mesodermal pattern and pattern repeats in the starfish bipinnaria larva, and related patterns in other deuterostome larvae and chordates. Philosophical Transactions of the Royal Society London, B 351: 1737–1758. | |
| Pridmore PA, Barwick RE and Nicoll RS (1997) Soft anatomy and the affinities of conodonts. Lethaia 29: 317–328. | |
| Purnell MA and Donoghue PCJ (1997) Architecture and functional morphology of the skeletal apparatus of ozarkodinid conodonts. Philosophical Transactions of the Royal Society London, B 352: 1545–1564. | |
| Wada H and Satoh N (1994) Details of the evolutionary history from invertebrates to vertebrates, as deduced from the sequences of 18S rDNA. Proceedings of the National Academy of Sciences, USA 91: 1801–1804. | |
| Williams NA and Holland PWH (1998) Molecular evolution of the brain. Brain Behaviour and Evolution 52: 177–185. | |
| book Young JZ (1981) The Life of Vertebrates, 3rd edn. Oxford: Clarendon Press. | |
| book Zug GR (1993) Herpetology, An Introductory Biology of Amphibians and Reptiles. London: Academic Press. | |
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