Exam 3

• Deuterostomes


  Monophyletic, but morphologically different clade

  Radial cleavage

  Intermediate development

  Blastophore becomes anus

  Coelom via mesoderm budiing from wall of archenteron
• The Deuterostomes


  Phylum Hemichordata

  • Entropneusts (acorn worms)
  • Pterobranchs (graptolites)

  Phylum Echinodermata

  Phylum Chordata

  • Cephalochordates
  • Urochordates
  • Vertebrates
• Xenacoelomorpha


  Lack several features sommon to most bilaterians eg. circulatory system, anus

  Phylogenetic position debated

  Sister group to all remaining bilateria

  Clade inside deuterostome

  Taxa solit betweem sister group + inside deuterostomes
• Echinoderms

  • Synapomorphies
  • Bilateral symmetry in larvae, pentaradial in adults
  • Water vascular system
  • Stereom = unique medodermal sketeon covered by thin epidermis
  • Multiple collagenous tisue
  • spines+pedicellariae
  • simple nervous system