Chapter 1

• Chordates (Super phylum Chordata)


  A group of animals that includes the vertebrates, together with several closely related invertebrates
• Chordates


  • Have, 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 that the true qualifier should be pharyngeal pouches rather than slits
• Phyla of the Super phylum Chordata

  • Urochordata
  • Cephalochordata
  • 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
• Vertebrates (except Hagfish)


  The dorsal hollow nerve cord has been surrounded with cartilaginous or bony vertebrae and the notochord generally reduced
• Deuterostomes


  • The three phyla of chordates
  • Hemichordates
  • Echinoderms
• Many of the taxa listed do not match traditional classes because several of those classes are paraphyletic
• Extant groups of chordates

  • Vertebrates (fishes, amphibians, reptiles, birds, mammals)
  • Hagfishes
  • Tunicates (Urochordata)
  • Lancelets (Cephalochordata)
  • Some odd extinct groups
• Chordates (with few exceptions)

  • Active animals with bilaterally symmetric bodies that are longitudinally differentiated into head, trunk and tail
  • Have the most distinctive morphological features of the notochord, nerve cord, and visceral clefts and arches