Bilateralia

• Origin of an antero-posterior axis (over an oral-aboral axis)
• Triboblastic: origin of mesoderm
• Coelomate:
  • Presence of a coelom, or internal body chamber, surrounded by mesoderm
  • Allowing for increased gut capacity, more sophisticated musculature, etc.
  • Complete digestive tract: mouth, gut, anus
  • Variously developed as pseudocoelomate, schizocoelomate (protostomes), enterocoelomate (deuterostomes)

Basal bilateralians include acoelomate flatworms and two (probably) larger clades:

• Deuterostomia
  • Blastopore becomes anus; mouth comes from secondary opening
  • Enterocoelomate
  • Indeterminate, radial cleavage of embryonic cells (ability to twin)
  • Nerve chord dorsal to digestive tract
• Protostomia
  • Blastopore becomes mouth
  • Schizocoelomate
  • Determinate, spiral cleavage (all mesoderm from 4d cell)
  • Nerve chord ventral to digestive tract
  • Divided into several major clades, two of which have big fossil record:
    • Ecdysozoa
    • Lophotrochozoa, further divided into:
      • Trochozoa
        • Trochophore larva
        • Annelida and Mollusca, only members with substantial fossil record
      • “Lophophorata”
        • Dubious monophyly on molecular work, but some morphological traits in common

Lophophorates share:

• Lophophores
  • Hollow extensions of second (of three) coeloms
  • Surround mouth, anus outside
  • Cilliated
• Essentially headless
• U-shaped guts
• Two major (possibly diphyletic) groups: Bryozoa and (Phoronida + Brachiopoda)

Bryozoa

• Exclusively colonial
• Non-living skeleton (zooecium)
• Each “individual” is a zooid
• Colony (zoarium) begins with an ancestrula
• Individual zooids connected by funiculus

• Phylactolaemata: non-calcareous, Cenozoic-only range, freshwater
• Gymnolaemata: Ordovican onward, probably paraphyletic, box-like zooids. Includes
  • Cheilostomata: Jurassic onward, excellent fossil record, encrusters
• Stenolaemata: Ordovician onward. Cylindrical zooids. Includes
  • Cyclostomata/Tubuliporata (Ordovician onward)
  • Cystoporata (Ordovician-Permian)
  • Trepostomata (Stony Bryozoans, Ordovician-Triassic)
  • Cryptostomata (Ordovician-Permian)
  • Fenestrata (Lacy Bryozoans, Ordovician-Permian)

Brachiopoda & Phoronida: Larger bodied. DNA strongly suggests two form a clade.

Brachiopoda:

• Always solitary
• Always encased in shell
• Always benthic marine

Major clades:

• Lingulata (sometimes called "Linguliformes" or "Linguliformea"):
  • Early Cambrian onward
  • Chitinophosphatic valves, lacking hinge articulation
  • Muscular pedicle
  • Burrowing infaunal habit
• Inarticulata proper (sometimes called "Craniiformea" or ”Craniata” (not to be confused with the TRUE Craniata)
  • Early Cambrian onward
  • Calcareous valves, lacking hinge articulation
  • Pedicle reduced or absent
  • Epifaunal
• Articulata (sometimes "Rhynchonelliformea")
  • Greatest diversity of brachiopods, living or extinct
  • Late Cambrian onward
  • Calcareous valves with complex hinge articulation
  • Pedicle variously developed, but dead horny tissue
  • Epifaunal, with a wide variety of habits

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