• The earliest vertebrates were jawless fish, similar to living hagfish.
  • The first fish with a complete vertebral column evolved about 450 million years ago.
  • Early bony fish evolved into modern ray-finned and lobe- finned fish.
  • The phylogenetic tree in Figure below gives an overview of vertebrate evolution.
  • As more data become available, new ideas about vertebrate Evolution emerge.
  • The earliest vertebrate evolved almost 550 million years old.
  • Until mammals and birds evolved, all vertebrate were ectothermic.
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