Phylum:Brachiopoda

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BRACHIOPODS

• Phylum Brachiopoda
• Class Articulata
• Long hinged type - Palaeozoic
• Short hinged type more common in Mesozoic

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MORPHOLOGY

• a typical articulate brachiopod.
• They have 2 VALVES (shells) that totally enclose
  the soft parts.
• The average size is 20 - 70 mm but can range up
  to 370 mm.
• The valves can open and are hinged at one end
  muscles open and close the shell.

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Morphology 2

• they are filter feeders extracting food from
  seawater.
• The two valves are different in size (as opposed
  to bivalves).
• However they do show a line of lateral symmetry
  along the middle of the animal.

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Morphology 3Naming of the valves

• The smaller valve is the BRACHIAL valve (upper in
  life position).
• The larger valve is the PEDICLE valve (lower in
  life position).
• The animal secretes the valves as it grows, the
  original small shell is called the UMBO and the
  shell grows outwards from either side of this
  point.

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Morphology 4

• Often the pedicle valve has a small circular
  opening (FORAMEN) at the end through which a type
  of foot extends called the PEDICLE.
• The pedicle allows the brachiopod to attach
  itself to the sea floor.

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Morphology 5

• Some shells like rhynchonellids have a zigzag
  COMMISURE with FOLDS (one on either side of the
  sulcus) and a SULCUS (in the middle).
• Folds have inhalent and sulcus has the exhalent.
• The currents are therefore separated.
• The crenulated commissure also provides a greater
  surface area.

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INTERNAL FEATURES

• inside the shell is the MANTLE CAVITY and the
  LOPHOPHORE, which is a food gathering and
  water-filtering device.
• At the posterior end is the pedicle which anchors
  the shell to a rock.
• The main muscles are the ADDUCTOR and DIDUCTOR
  muscles, which were used to close the shell.

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Internal morphology 2

• there are scars left from where the muscles were
  attached to the shell.
• The CARDINAL PROCESS acts as a fulcrum on which
  the muscles can pull.
• The diductor muscles contract and pull down the
  cardinal process and open the shell.
• The adductor muscles contract to close the shell.
  

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Internal Morphology 3

• the lophophore is a feeding device, which
  collects suspended particles.
• Some brachiopods like spiriferids have a spiral
  calcite support called a lophophore support or
  spiralia.

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Internal morphology 4

• On the diagram you can see that the brachiopod
  has TEETH (pedicle valve) and SOCKETS (brachial
  valve).
• The role of these is to help the hinge line to
  stay in position

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Articulate brachiopods' mode of life.

• They tended to live in shallow marine conditions
  (up to 500 m).
• Modern forms live in cool - temperate waters
  around the Pacific (Japan, S. Australia, New
  Zealand, N. Atlantic and W. Scotland).
• As there are modern day equivalents we know their
  environments

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