fossils & evolution—brachiopoda1 brachiopods—stuff to know bold font terms in text...

Fossils & Evolution—Brachiopoda 1

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)


Living brachiopods


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


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


Brachiopod diversity


Classification

O rde r Lingu lidaE a rly C am b ria n-R e ce n t

C lass Ina rticu la tam o stly p ho sph a tica rt icu la tion a bse n t

E a rly C am b ria n-R e ce n t

O rde r O rth idaE a rly C am b ria n -P e rm ian

O rde r Strophom en idaO rd o v ic ia n -T ria ss ic

O rde r P en tam eridaM id d le C a m bria n -D evo n ian

O rde r Rhynchone llidaO rd o vic ia n -R e ce n t

O rde r Sp ir ife r idaO rd o v ic ian -Ju ra ss ic

O rder T e reb ratu lidaE a rly D e vo n ia n -R e ce n t

C lass A rticu la taca lc it ic

a rt icu la tio n by tee th a n d so cke tsE a rly C am b ria n-R e ce n t

Phylum BrachiopodaE a rly C am b ria n-R e ce n t


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


Brachiopod morphology


Hinge, teethand sockets


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)


Shell ornamentation


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


Posterior region

“beak”


Posterior region (cont.)

Among articulate forms,those with a hinge lineare strophic; thosewithout are astrophic

astrohpic

strophic


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


Internal soft anatomy


Musculature(valves tend toclose and stayclosed upondeath)


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)


Lophophore types

brachia


Lophophore supports

spiralia spiralialoopedbrachidia

loopedbrachidia


Class Inarticulata

• Lingula ia an example of a “living fossil”

• Relatively low diversity since Ordovician time

• Infaunal, with long fleshy pedicle


Inarticulate brachiopods(Lingula et al.)


Order Orthida Strophic; unequally biconvex valves; usually with well-developed delthyrium/notothyrium openings in interareas


Order Strophomenida Strophic; convex ventral valve/concave dorsal valve


Order Strophomenida Strophic; convex ventral valve/concave dorsal valve

(Suborder Productina)


Order Pentamerida Strophic or astrophic; strongly biconvex with incurved

beaks; open delthyrium with spoon-shaped structure (“spondylium”)


Order RhynchonellidaAstrophic; biconvex shell with dorsal fold and ventral sulcus


Order Spiriferida Variable shell form; spiralia supports for lophophore

(Suborder Spiriferina)



(Suborder Atrypina)



(Suborder Athyrina)


Order Terebratulida Astrophic (rarely strophic); biconvex shell; loop supports for

lophophore

Cererithyris(Jurassic)

fossils & evolution—brachiopoda1 brachiopods—stuff to know bold font terms in text...

Documents

posterior region pedicle

pedicle valve sockets

pedicle valvelower

pedicle valvenotothyrium

pedicle valveanterior

end of shell

anterior region of shell

valvedorsal valve