Chordata
From Palaeos
| DEUTEROSTOMIA | |
| Taxonomy | Phylogeny |
Domain: Eukarya
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Bilateria `--Deuterostomia |--Vetulicolia |--Yunnanozoa |--+--Xenoturbella | `--Ambulacraria | |?--Dinomischida | |--Hemichordata | `--+--Vetulocystidae | `--+--Stylophora | `--+--Soluta | `--+--Cincta | `--+--Ctenocystoidea | `--+--Helicoplacoidea | `--+--Edrioasteroidea | `--Echinodermata `--Chordata |--Urochordata `--+--Cephalochordata `--Craniata `--Vertebrata |
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Deuterostomia topics: Fossil Record | Characteristics | The Fall and Rise of Orders of Symmetry | Ecology and Lifestyle | Links | References |
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Chordates (phylum Chordata) are a group of animals that includes the vertebrates, together with several closely related invertebrates. They are united by having, at some time in their life, a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a muscular tail extending past the anus. Some scientists argue, however, that the true qualifier should be pharyngeal pouches rather than slits.[citation needed]
The phylum Chordata is broken down into three subphyla: Urochordata, Cephalochordata, and Vertebrata. Urochordate larvae have a notochord and a nerve cord but they are lost in adulthood. Cephalochordates have a notochord and a nerve cord but no vertebrae. In all vertebrates except for Hagfish, the dorsal hollow nerve cord has been surrounded with cartilaginous or bony vertebrae and the notochord generally reduced.
The chordates and two sister phyla, the hemichordates and the echinoderms, make up the deuterostomes, a superphylum.
The extant groups of chordates are related as shown in the phylogenetic tree, below. They do not match up very well with the traditional groups, and as a result vertebrate classification is in a state of flux, although their relationships are not very well understood
| CHORDATA - The Chordates | |||
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o Chordata |--Urochordata) | |--Larvacea | `--+--Ascidiacea | `--Thaliacea `--+--Cephalochordata `--+--Haikouella `--o Craniata |--Myxinoidea `--Vertebrata |
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[edit] Chordata fossil record
<--the following diagram to be made more detailed -->
[edit] Phylogeny
<==Chordata [Acraniata] | i. s.: Cathaymyrus diadexus |--Branchiostoma [Acrania, Cephalochordata] | |--B. belcheri | |--B. floridae | `--B. lanceolatum [=Limax lanceolatus] `--Craniata [Agnatha, Craniota] | i. s.: Pipiscius zangerli | Myllokunmingia |--+--Myxinikela siroka | `--Myxinidae `--+--Haikouichthys ercaicunensis `--Vertebrata
* Type species of genus indicated
[edit] References
Boorman, C. J., & S. M. Shimeld. 2002. The evolution of left-right asymmetry in chordates. BioEssays 24 (11): 1004-1011.
Conway Morris, S. 1998. The Crucible of Creation. Oxford University Press: Oxford.
Gee, H. 2003. You aren’t what you eat. Nature 424: 885-886.
Giribet, G., D. L. Distel, M. Polz, W. Sterrer & W. C. Wheeler. 2000. Triploblastic relationships with emphasis on the acoelomates and the position of Gnathostomulida, Cycliophora, Plathelminthes, and Chaetognatha: A combined approach of 18S rDNA sequences and morphology. Systematic Biology 49: 539-562.
Martini, F. H., & D. Flescher. 2002. Hagfishes. Family Myxinidae. In Bigelow and Schroeder’s Fishes of the Gulf of Maine (B. B. Collette & G. Klein-MacPhee, eds.) 3rd ed. pp. 9-16. Smithsonian Institute Press: Washington.
Shu, D.-G., L. Chen, J. Han & X.-L. Zhang. 2001. An Early Cambrian tunicate from China. Nature 411: 472-473.
Shu, D., S. Conway Morris, X.-L. Zhang, L. Chen, Y. Li & J. Han. 1999. A pipiscid-like fossil from the Lower Cambrian of south China. Nature 400: 746-749.
Shu, D.-G., S. Conway Morris, J. Han, Z.-F. Zhang, K. Yasul, P. Janvier, L. Chen, X.-L. Zhang, J.-N. Liu, Y. Li & H.-Q. Liu. 2003. Head and backbone of the Early Cambrian vertebrate Haikouichthys. Nature 421: 526-529.
Credits
phylogeny CKT070909
