Evolutionary Systematics

• Deuterostomes:

  • bilateral symmetry
  • pharyngeal slits (Rachenspalten)
  • blastopore becomes the anus
  • mesoderm buds off from the gastrula
• Chordates:

  • dorsal, hallow nerve cord
  • ventral heart
  • dorsal supporting rod (notochord)
  • tail that extends after anus
• Vertebrates:

  • phalangeal arches in all embryos
  • those arches get lost over time and evolve into f.e. gill arches and jaws in fish
  • jointed, dorsal vertebral column instead of a notochord
  • anterion skull enclosing brain
  • well-developed circulatory system
  • not all have a jaw
  • Examples: fish, turtles, mammals, birds
• Tunicates:

  • only show the chordate features as larvae
  • filter-feeders
  • have a protective tunic-like shell
  • Examples: sea squirts, salps
• Lancelets:

  • 35 species
  • small and simple