Chordate

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 dorsal hollow neural tube, and a muscular tail extending past the anus. Some scientists argue, however, that the true qualifier should be pharyngeal pouches rather than slits.

Related Topics:
Phylum - Vertebrate - Invertebrate - Notochord - Pharyngeal slit - Tail

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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 In vertebrates, the notochord has been replaced by a bony vertebral column.

Related Topics:
Urochordata - Cephalochordata - Vertebrata - Vertebra

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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.

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Chordata

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