Wikipedia

Chordate

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Template:Taxobox begin Template:Taxobox begin placement Template:Taxobox regnum entry Template:Taxobox subregnum entry Template:Taxobox phylum entry Template:Taxobox end placement Template:Taxobox section subdivision 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 Template:Taxobox end

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 In vertebrates, the notochord has been replaced by a bony vertebral column.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

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