What are Lophophorates?

• "Crest or tuft bearer"
• Includes 3 phyla: Bryozoans, Brachipods, Phoronids
• All have a circular or horseshoe-shaped fold of the anterior body wall that bears feeding tentacles
• All are suspension feeders
• Most have a colonial hydroid-like structure, others are solitary worm-like or bivalve-like animals
• Bryozoans and Brachiopods are important and even dominant animal groups in the fossil record

Lophophorate Evolution

• A mixture of protostome and deuterostome traits:
  • Tricoelomate, radial cleavage, indeterminate development (deuterostome)
  • usually blastopore becomes mouth (protostome)
• Molecular evidence supports a protostome affinity

Phylum Bryozoa

• "Moss Animals"
• 5000 living species and 15,000 fossil species
• Mostly marine, some freshwater species
• All are sessile colonies
• May be abundant, but small and inconspicuous

Characteristics of Bryozoa

1. Zooids are small (<1 mm), attached to a branched trunk

2. Body covered with a chitinous cuticle (may be calcified)

3. Zooids are tricoelomate, tentacles are folds of mesoderm

4. Lophophore is slowly protruded by coelomic fluid and rapidly withdrawn by retractor muscles

5. Feeding tentacles bear cilia that move food particles

6. U-shaped digestive tract, anus exits below lophophore

7. Lack an excretory system (sequester N wastes); rudimentary circulatory system

8. As a colony grows and divides, old zooids degenerate or become defensive avicularia with movable jaws

Phylum Brachiopoda

• "Arm-Footed", lamp shells
• 350 living species, but 30,000 fossil species
• Dominant group in Ordivician fossils (SW Ohio)
• Resemble Molluscs, and were not separated as a phylum until the middle 19th century

Characteristics of Brachiopoda

1. Two Basic Types

• Articulate - CaCO3 hinged bivalve shell
• Inarticulate - CaPO4 and chitin unhinged bivalve shell

2. Characteristics of Bivalve Shell

• Valves are D-V rather than lateral as in bivalves
• Ventral valve is usually larger than dorsal valve
• Each valve of shell has A-P symmetry (bivalves do not)

3. Pedicle or stalk exits by through a hole in ventral plate

• Articulates - pedicle is solid for attachment to hard surface
• Inarticulates - pedicle is muscular to move through mud / sand

4. Internal Structures

• Posterior end (pedicle) encloses all viscera within a single coelom
• Anterior portion bears a complex folded lophophore