Exam II Rescheduled

• Lecture Exam II will be given on Thursday, April 27, instead of Thursday, April 20.
• Format (types and approximate number of questions) will be the same as in Lecture Exam I.
• I will be available for questions or discussion in the sunny part of the Student Union (outside McDonald's) from 11:00-1:00 on Thursday, April 20.

Deuterostomes
Origins and Relationships

Deuterostome Synapomorphies

• Enterocoely (coelom develops as outpockets of archenteron)
• Radial cleavage
• Indeterminate development
• Blastopore forms anus
• Tripartite coelom (mesoderm)
• protocoel
• mesocoel
• metacoel

Deuterostomes - Major Groups

• The Lophophorates
• Phylum Phoronida
• Phylum Bryozoa (Ectoprocts, "moss animals")
• Phylum Brachiopoda ("lamp shells")
• Phylum Echinodermata
• Phylum Hemichordata
• Phylum Chordata

Deuterostome Relationships (cladogram)

The Lophophorates

• Feed with horseshoe-shaped "lophophore" -- filtering structure
• Remnants of early Paleozoic deuterostome evolutionary experiments
• Three Phyla:
• Phoronida
  • Morphology suggests that they are primitive, but few fossils
  • Only a few species survive, these only in "refuge" habitats (e.g., intertidal mud and sand flats) that are relatively free of competition and predation
• Brachiopoda: "lamp shells" (similar to early oil lamps)
  • Extremely important sessile epibenthic filter feeders in the Paleozoic (one of the dominant forms in early and mid-Paleozoic seas)
  • Were mostly eliminated by the burrowing "bioturbators" that evolved during the late Paleozoic (Carboniferous), throwing sediments up and smothering, clogging filtering structures (recall bioturbators evolved due to rise of land plants, decaying biomass enriched coastal sediments)
  • Survive today only in "refuges" -- bioeroded holes in coral reefs, caves, vertical walls, deep water
• Bryozoa: "moss animals"
  • Extremely important sessile epibenthic filter feeders in the Paleozoic (one of the dominant forms in early and mid-Paleozoic seas)
  • Were mostly eliminated by the burrowing "bioturbators" that evolved during the late Paleozoic (Carboniferous) and clogged feeding structures of sessile filter feeders
  • Surrvive today primarily in "refuges" from predators, competitors, bioturbators -- bioeroded holes in coral reefs, caves, vertical walls

Lophophorate
Synapomorphies

• U-shaped gut
• Lophophore

Lophophorate
Characteristics

• All Marine
• Benthic
• Suspension feeders
• Encased in tube or shell
• Hence the U-shaped gut
• All were important epibenthic suspension feeders in early Paleozoic
• Bioturbators in Carboniferous likely greatly decreased their success
• Survive only in "refuge" environments today

Phylum Echinodermata

• Five living classes
• Crinoidea
  • Sea lilies, feather stars
  • Mouth dorsal
  • Relatively sessile
• Asteroidea
  • Sea stars, starfish
• Ophiuroidea
  • Brittle stars, basket stars
• Echinoidea
  • Sea urchins, sand dollars, heart urchins
  • No arms
  • Ossicles fused as test
• Holothuroidea
  • Sea cucumbers
  • Body elongate
  • Rests on side
  • Ossicles tiny

Phylum Echinodermata
Synapomorphies

• Calcareous endoskeletal plates
• Pentaradial symmetry
• Bilateral as larvae
• Various types of symmetry in fossils
• Water vascular system

Phylum Hemichordata

• Sister group of Chordates
• Dorsal, hollow nerve cord
• Pharyngeal slits
• Includes
• Enteropneusta - Acorn worms
• Pterobranchia

Phylum Chordata

• Three subphyla
• Urochordata
• Cephalochordata
• Craniata (~ Vertebrata)
• Synapomorphies
• Notochord
• Post-anal tail
• Endostyle