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<tr><th bgcolor=pink>Scientific classification
<tr><td>
<tr><td>Kingdom:<td>Animalia
<tr><td>Subkingdom:<td>Deuterostomia
<tr><td>Phylum:<td>Chordata
</table>
<tr><th bgcolor=pink>Typical Classes
<tr><td>
Subphylum Urochordata - Tunicates
Ascidiacea
Thaliacea
Larvacea
Subphylum Cephalochordata - Lancelets
Subphylum Myxini - Hagfishes
Subphylum Vertebrata - Vertebrates
Petromyzontida - Lampreys
Placodermi (extinct)
Chondrichthyes - Cartilaginous fishes
Acanthodii (extinct)
Actinopterygii - Ray-finned fishes
Actinistia - Coelacanths
Dipnoi - Lungfishes
Amphibia - Amphibians
Reptilia - Reptiles
Aves - Birds
Mammalia - Mammals
</table>
Chordates (phylum Chordata) include the vertebrates, together with several closely related invertebrates. They are united by having, at some stage in their life, a notochord, a hollow dorsal nerve cord, pharyngeal slits, a tail extending past the anus, and bands of muscles that go around the body.
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 In vertebrates, the notochord has been replaced by a bony vertebral column.
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 very well understood.
Chordata
ca:Cordat
da:Rygstrengsdyr
de:Chordatiere
et:Keelikloomad
es:Cordado
eo:Ĥordulo
fr:Cord
ia:Chordatos
it:Cordati
he:מיתרניים
nl:Chordata
ja:脊索動物
oc:Chordata
pl:Strunowce
pt:Cordado
ru:Хордовые
fi:Selkjnteiset
sv:Ryggstrngsdjur
uk:Хордові
zh:脊索动物
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