Brachiopods are marine invertebrates with hard shells known as valves. They are divided into two classes - Articulata and Inarticulata. Articulata have valves that are hinged and can open, while Inarticulata valves are cemented together and cannot open. Brachiopods live with their lophophore protruding between the valves to filter feed on plankton. Their shells have distinct features like teeth and sockets that interlock the valves together. Brachiopods were most common in the Paleozoic era and remain important index fossils for determining paleoenvironments.

1.  Phylum:Phylum: BrachiopodaBrachiopoda
 Classes:Classes:ArticulataArticulata
 InarticulataInarticulata
 Orders:Orders: 7 Articulate 7 Articulate
 4 Inarticulate4 Inarticulate

2.  Copy diagram on pageCopy diagram on page
125 a) and b) Black125 a) and b) Black to show to show
a typical articulate a typical articulate
brachiopod.brachiopod.
 They have 2 They have 2 VALVESVALVES
(shells) that totally enclose (shells) that totally enclose
the soft parts.the soft parts.
 The average size is 20 - 70 The average size is 20 - 70
mm but can range up to 370 mm but can range up to 370
mm.mm.
 The valves can open and are The valves can open and are
hinged at one end; muscles hinged at one end; muscles
open and close the shell.open and close the shell.

3. Morphology 2Morphology 2
 They usually allow water into They usually allow water into
the shell, as they are filter the shell, as they are filter
feeders extracting food from feeders extracting food from
seawater.seawater.
 The two valves are different The two valves are different
in size (as opposed to in size (as opposed to
bivalves).bivalves).
 However; they do show a However; they do show a
line of lateral symmetryline of lateral symmetry
along the middle of the along the middle of the
animalanimal. . Highlight this onHighlight this on
your diagramyour diagram..

4. Morphology 3:Morphology 3:Naming of the valvesNaming of the valves
 The smaller valve is the The smaller valve is the
BRACHIALBRACHIAL valve (upper in valve (upper in
life position).life position).
 The larger valve is the The larger valve is the
PEDICLEPEDICLE valve (lower in life valve (lower in life
position).position).
 The animal secretes the The animal secretes the
valves as it grows, the valves as it grows, the
original small shell is called original small shell is called
thethe UMBOUMBO and the shell and the shell
grows outwards from either grows outwards from either
side of this point. side of this point. Make sureMake sure
that you can see the umbothat you can see the umbo
on a hand specimen.on a hand specimen.

5. Morphology 4:Morphology 4:
 Often the pedicle valve has aOften the pedicle valve has a
small circular openingsmall circular opening
((FORAMENFORAMEN) at the end) at the end
through which a type of footthrough which a type of foot
extends called theextends called the
PEDICLEPEDICLE.. Make sure thatMake sure that
you can see the foramen inyou can see the foramen in
a hand specimen.a hand specimen.
 The pedicle allows theThe pedicle allows the
brachiopod to attach itself tobrachiopod to attach itself to
the sea floor.the sea floor.
 Inside the shell the body fillsInside the shell the body fills
much of the body cavity.much of the body cavity.

6. Morphology 5:Morphology 5:
 Some shells like rhynchonellidsSome shells like rhynchonellids
have ahave a wrinkly COMMISUREwrinkly COMMISURE
withwith FOLDSFOLDS (one on either(one on either
side of the sulcus)side of the sulcus) and aand a
SULCUS (in the middle)SULCUS (in the middle)..
 Draw a rhynchonellid showingDraw a rhynchonellid showing
the fold and sulcus and thethe fold and sulcus and the
inhalentinhalent andand exhalentexhalent currents.currents.
 Folds have inhalent and sulcusFolds have inhalent and sulcus
has the exhalent.has the exhalent.
 The currents are thereforeThe currents are therefore
separated.separated.
 The crenulated commissureThe crenulated commissure
also provides a greater surfacealso provides a greater surface
area.area.

7.  The inside of the shell is theThe inside of the shell is the
MANTLE CAVITYMANTLE CAVITY and is mainlyand is mainly
thethe LOPHOPHORE, whichLOPHOPHORE, which is ais a
food gathering and water-food gathering and water-
filtering device.filtering device.
 Draw diagram (d) fromDraw diagram (d) from
page 125 Black.page 125 Black.
The important muscles are:The important muscles are:
 At the posterior end is theAt the posterior end is the
pedicle “foot” type ofpedicle “foot” type of
ligament/muscle which whenligament/muscle which when
extended could usually reachextended could usually reach
outside of the shell.outside of the shell.
 The main muscles were theThe main muscles were the
ADDUCTOR and DIDUCTORADDUCTOR and DIDUCTOR
muscles, which were used tomuscles, which were used to
close the shell.close the shell.

8. Internal morphology 2:Internal morphology 2:
 Draw diagrams from pageDraw diagrams from page
125 Black:125 Black:
 c)c) for muscle position.for muscle position.
 e) and f)e) and f) showing internal viewsshowing internal views
of shells with muscle scars.of shells with muscle scars.
 Both sets of muscles wereBoth sets of muscles were
attached to the shell andattached to the shell and
although not preserved in thealthough not preserved in the
fossils there are scars left fromfossils there are scars left from
where the muscles werewhere the muscles were
attached to the shell.attached to the shell.
 TheThe CARDINAL PROCESSCARDINAL PROCESS andand
HINGEHINGE acts as a fulcrum onacts as a fulcrum on
which the muscles can pull.which the muscles can pull.
 The diductor muscles contractThe diductor muscles contract
and pull down the cardinaland pull down the cardinal
process and open the shell.process and open the shell.

9. Internal Morphology 3:Internal Morphology 3:
 As the diductor musclesAs the diductor muscles
relax the adductor musclesrelax the adductor muscles
contract and close the shell.contract and close the shell.
 Role of theRole of the lophophorelophophore is tois to
act as a feeding device,act as a feeding device,
which collects suspendedwhich collects suspended
particles.particles.
 Some brachiopods likeSome brachiopods like
spiriferids have a spiralspiriferids have a spiral
calcite support called acalcite support called a
lophophore support orlophophore support or
spiralia.spiralia.
 Draw diagram d on pageDraw diagram d on page
137.137.

10. Internal morphology 4:Internal morphology 4:
 On the diagram you can seeOn the diagram you can see
that the brachiopod hasthat the brachiopod has
TEETHTEETH (pedicle valve) and(pedicle valve) and
SOCKETSSOCKETS (brachial valve).(brachial valve).
 What do you think the role ofWhat do you think the role of
these are?these are?

11. Articulate Brachiopod Orders:Articulate Brachiopod Orders:
 There are 7 orders.There are 7 orders.
(including Productids).(including Productids).
 For each draw a simpleFor each draw a simple
diagram.diagram.
 Make a note of the typeMake a note of the type
of hinge line:of hinge line:
 Long orLong or
 ShortShort

12.  They tended to live inThey tended to live in
shallow marine conditionsshallow marine conditions
(up to 500 m but may go(up to 500 m but may go
down to 6, 000m).down to 6, 000m).
 Modern forms live in cool -Modern forms live in cool -
temperate waters around thetemperate waters around the
Pacific (Japan, S. Australia,Pacific (Japan, S. Australia,
New Zealand, N. AtlanticNew Zealand, N. Atlantic
and W. Scotland).and W. Scotland).
 As there are modern dayAs there are modern day
equivalents we know theirequivalents we know their
environments and so theyenvironments and so they
are good palaeoenvironmentare good palaeoenvironment
indicators (indicators (index fossilsindex fossils).).

13. Index fossils etc.Index fossils etc.
 Define an index fossil:Define an index fossil:
 A fossil that is restricted to aA fossil that is restricted to a
particularparticular
palaeoenvironment.palaeoenvironment.
 Corals mare perhaps theCorals mare perhaps the
best index fossils.best index fossils.
 The most commonThe most common
question regardingquestion regarding
Brachiopods is how to tellBrachiopods is how to tell
the difference betweenthe difference between
them and Bivalves.them and Bivalves.
 We will cover this next whenWe will cover this next when
we look at Bivalves.we look at Bivalves.

14.  Brachiopods are a long-livedBrachiopods are a long-lived
Phylum ranging from thePhylum ranging from the
Cambrian to Present.Cambrian to Present.
 They were very common inThey were very common in
the Palaeozoic and slightlythe Palaeozoic and slightly
less so in the Mesozoic butless so in the Mesozoic but
still remain important.still remain important.
 In the Present not manyIn the Present not many
forms are left withforms are left with
approximately 70 Genera.approximately 70 Genera.
 Over 2500 fossil Genera areOver 2500 fossil Genera are
known.known.
 The largest were found inThe largest were found in
the Cambrian (370 mm).the Cambrian (370 mm).