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Chordates
Yellowfin tuna, Thunnus albacares
Yellowfin tuna, Thunnus albacares
Scientific classification
Domain: Eukaryota
Kingdom: Animalia
Superphylum: Deuterostomia
Phylum: Chordata
Bateson, 1885
Typical Classes
  • Subphylum Urochordata - Tunicatas
    • Ascidiacea
    • Thaliacea
    • Larvacea
  • Subphylum Cephalochordata - Lancelets
  • Subphylum Myxini - Hagfishes
  • Subphylum Vertebrata - Vertebrates
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 stage 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.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 In vertebrates, the notochord has been replaced by a bony vertebrae.The chordates and two sister phyla, the hemichordates and the echinoderms, make up the deuterostomes, a superphylum.The extant groups of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
  • Urochordata (tunicates)
  • Cephalochordata (lancelets)
  • Craniata (animals with skulls)
    • Myxini or Hyperotreti (hagfish)
    • Vertebrata (animals with backbones)
      • Cephalaspidomorphi (lampreys)
      • Gnathostomata ( jawed vertebrates)
        • Chondrichthyes (cartilaginous fish)
        • Teleostomi (bony fish, ~ Osteichthyes)
          • Actinopterygii (ray-finned fish)
          • Sarcopterygii (lobe-finned fish)
            • Actinistia ( coelacanths)
            • Dipnoi (lungfishes)
              • Tetrapoda (four-legged vertebrates)
                • Amphibia (amphibians)
                • Amniotes (amniotic egg)
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