Brachiopods—Stuff to know
• Bold font terms in text
• Classification and stratigraphic ranges of
Classes and Orders
• Be able to identify correct Order for any
given specimen (not necessary to identify
genera)
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Living brachiopods
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Brachiopoda—Phylum overview
• Solitary (but individuals often live in clusters)
• Bivalved, with each valve being bilaterally
symmetrical
• Marine; mostly shallow marine (100–200m), but
can occur in depths >2000m
• Attached by pedicle or unattached; some
infaunal
• Filter feeders
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Brachiopoda—Phylum overview
• Possibly share a common ancestor with bryozoans
(both groups possess a lophophore)
• Stratigraphic range is Early Cambrian to Recent
• Peak diversity in Ordovician, Devonian,
Permian
• Major reduction coincident with end-Permian
mass extinction
• Mesozoic peak diversity in Jurassic
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Brachiopod diversity
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Classification
Phylum Brachiopoda
Early Cambrian-Recent
Class Inarticulata
Class Articulata
mostly phosphatic
articulation absent
Early Cambrian-Recent
calcitic
articulation by teeth and sockets
Early Cambrian-Recent
Order Lingulida
Order Orthida
Order Strophomenida
Early Cambrian-Recent
Early Cambrian-Permian
Ordovician-Triassic
Order Pentamerida
Order Rhynchonellida
Middle Cambrian-Devonian
Ordovician-Recent
Order Spiriferida
Order Terebratulida
Ordovician-Jurassic
Early Devonian-Recent
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Brachiopod morphology
• Ventral valve (a.k.a. “pedicle valve”)
– Lower or bottom valve
• Dorsal valve (a.k.a. “brachial valve”)
– Upper or top valve
• Foramen = pedicle opening (largely or entirely in
pedicle valve)
• Anterior = end of shell opposite foramen
• Posterior = end of shell containing foramen
• Commissure = line along which two valves meet
• Hinge = articulation mechanism
– Teeth in pedicle valve; sockets in brachial valve
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Brachiopod morphology
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Hinge, teeth
and sockets
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Brachiopod morphology
• Shells may be highly ornamented
–
–
–
–
–
Growth lines (concentric)
Ribs (radial)
Fold (major raised area)
Sulcus (major depressed area)
Spines (sometimes extensions of growth
lamellae; sometimes discrete structures)
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Shell ornamentation
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Features of the posterior region
(pedicle and hinge region)
• Pedicle opening
– Delthyrium = triagular opening in pedicle
valve
– Notothyrium = smaller opening in brachial
valve
– Interarea = planar or curved surface between
“beak” and hingeline
• Ventral interarea
• Dorsal interarea
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Posterior region
“beak”
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Posterior region (cont.)
Among articulate forms,
those with a hinge line
are strophic; those
without are astrophic
astrohpic
strophic
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Internal features
• Body cavity houses major organs in posterior
region of shell
• Mantle cavity in anterior region of shell is mostly
open space
• Lophophore = ciliated, arm-like structure that
serves for respiration and food gathering
• Pedicle = muscular stalk for attachment to
external objects or substrate
• Adductor and diductor muscles
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Internal soft anatomy
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Musculature
(valves tend to
close and stay
closed upon
death)
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Lophophore
• Usually a two-part structure, with each
half (brachium; plural brachia) leading to
the mouth
• May be complexly looped or coiled
• May be supported by a mineralized
structure—spiralium (plural spiralia) or
brachidium (plural brachidia)
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Lophophore types
brachia
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Lophophore supports
spiralia
looped
brachidia
looped
brachidia
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spiralia
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Class Inarticulata
• Lingula ia an example of a “living fossil”
• Relatively low diversity since Ordovician
time
• Infaunal, with long fleshy pedicle
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Inarticulate brachiopods
(Lingula et al.)
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Order Orthida
Strophic; unequally biconvex valves; usually with welldeveloped delthyrium/notothyrium openings in interareas
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Order Strophomenida
Strophic; convex ventral valve/concave dorsal valve
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Order Strophomenida
Strophic; convex ventral valve/concave dorsal valve
(Suborder Productina)
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Order Pentamerida
Strophic or astrophic; strongly biconvex with incurved
beaks; open delthyrium with spoon-shaped structure
(“spondylium”)
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Order Rhynchonellida
Astrophic; biconvex shell with dorsal fold and ventral sulcus
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Order Spiriferida
Variable shell form; spiralia supports for lophophore
(Suborder Spiriferina)
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Order Spiriferida
Variable shell form; spiralia supports for lophophore
(Suborder Atrypina)
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Order Spiriferida
Variable shell form; spiralia supports for lophophore
(Suborder Athyrina)
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Order Terebratulida
Astrophic (rarely strophic); biconvex shell; loop supports for
lophophore
Cererithyris
(Jurassic)
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