Lophophorates
Brachiopods and Bryozoans
Lophophores
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All lophophores we will note are filter feeders and have a calcareous shell.
There is one other group but without a shell, it left no fossil record.
We will look two phyla: Brachiopods and Bryozoans
Brachiopods
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Brachiopods are the most diverse and abundant fossils of the Paleozoic
Over 4500 fossil genera make them by far the most common fossil
They are useful as index fossils, for paleoecological and evolutionary studies
Fewer than 120 genera have survived to the recent
Brachiopods- morphology
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Brachiopods are classified on their shell characteristics
They are bivalves, but symmetry runs through the shell not between the two
halves
Muscle scars, dentition and shell characteristics are all used in classification
Brachiopods- systematics
Phylum Brachiopoda
Class Inarticulata – Common in Cambrian – Ordovician, still have living forms
(Lingula); no tooth and socket articulation; chitin/phosphate shells
Class Articulata – Cambrian – Recent; 95% of known genera; well developed
dentition, diductor muscle scars, calcite shells
Order Orthida – Cambrian –Permian
- considered most primitive
- long straight hinge and wide open triangular delthyrium and narrow
interarea
- most are gently biconvex with a circular outline
- Herbertella, Resserella, Dinorthis
Order Strophomenida – Ord – Triassic
- Variety of shape and characteristics, but the prominent “D” shape is
common; pseudopunctate
- Typically long straight hinge line and completely closed pedicle
foramen.
- Rafinesquina, Strophomena
Order Pentamerida – Cambrian – Devonian, index for the Silurian
- Most are biconvex with a curved hinge line and small uncovered
delthyrium; impunctate
- The large scooped spondylium, large septum and crurallium complex
divides the ventral shell into 5 parts
Order Spiriferida – Ord- Jurassic
- spiral brachidia, highly biconvex, radial costae, large interarea on
ventral valve and often a long hinge line
- Microspirifer, Neospirifer, Atrypa
Order Rhynchonellida – Ord – Recent
- short, bent hinge line, pointed beak,
Most have heavy ribs,deep fold and sulcus
Order Terebratulida – Dev – Recent
“Lamp shell” brachiopods, strongly biconvex with large pedicle foramen,
beak overhangs the short hinge line with no interarea. Best known living
form.
Brachiopods- paleoecology
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Exclusively sessile benthic marine forms
Found in shallow marine and in epicontinental platform seas
Some inarticulate forms tolerate brackish water, but most require clear water
with currents to bring food and oxygen to them and carry waste away.
Brachiopods - evolution
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Different groups characterize different periods
They were plentiful enough that their evolution can be traced and they are
widespread enough to be excellent index fossils for some periods.
Brachiopods- biostratigraphy
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Cambrian – Lingulid and Orthid
Ordovician – Strophomenides
Silurian – Pentamerids
Devonian – Spirifers
Mississippian – mixture of Spirifers and Productids
Pennsylvanian/Permian – Productids
Less important in the Mesozoic/Cenozoic
Bryozoans
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Bryozoans are colonial animals that have not always been classified as
lophophores.
The individual bryozoan animal (zooid) is very small – about 1mm long
Two of the three classes have a calcareous colonial skeleton that is preserved
in the fossil record.
The structure of the colonial skeleton is what separates the different orders
Bryozoans -systematics
 Phylum Bryozoa
Class Stenolaemata – Ordovician – Recent
Zoocia are long and tubular, highly calcified and grow throughout
the life of the colony
Bryozoans -systematics
 Phylum Bryozoa
Class Stenolaemata – Ordovician – Recent
Order Trepostomata – Ordovician - Triassic
Bryozoans -systematics
 Phylum Bryozoa
Class Stenolaemata – Ordovician – Recent
Order Trepostomata – Ordovician – Triassic
Formed massive branching colonies in the Paleozoic. Made up of
three kinds of zoocia. Contributed large parts of some Ord.
limestones. Survived the Paleozoic extinctions to become
extinct in the Triassic.
Bryozoans -systematics
 Phylum Bryozoa
Class Stenolaemata – Ordovician – Recent
Order Trepostomata – Ordovician – Triassic
Order Cryptostomata – Ordovician - Permian
Bryozoans -systematics
 Phylum Bryozoa
Class Stenolaemata – Ordovician – Recent
Order Trepostomata – Ordovician – Triassic
Order Cryptostomata – Ord – Permian
Large numbers before the Late Ord. extinctions and then
persisting to the end of the Permian when they became extinct.
Characterized by short autopores with a vestibule separated
from the inner zoocium by a hemiseptum.
Bryozoans -systematics
 Phylum Bryozoa
Class Stenolaemata – Ordovician – Recent
Order Trepostomata – Ordovician – Triassic
Order Cryptostomata – Ord – Permian
Order Fenestrata – Ordovician – Permian
Bryozoans -systematics
 Phylum Bryozoa
Class Stenolaemata – Ordovician – Recent
Order Trepostomata – Ordovician – Triassic
Order Cryptostomata – Ord – Permian
Order Fenestrata – Ordovician – Permian
Especially abundant in the Mississippian and became extinct at
the end of the Permian. Zooaria are arranged in a lacy network.
Key Genera Acrhimedes and Fenestella
Bryozoans -systematics
 Phylum Bryozoa
Class Stenolaemata – Ordovician – Recent
Order Trepostomata – Ordovician – Triassic
Order Cryptostomata – Ord – Permian
Order Fenestrata – Ordovician – Permian
Order Cyclostomata – Ordovician – Recent
Bryozoans -systematics
 Phylum Bryozoa
Class Stenolaemata – Ordovician – Recent
Order Trepostomata – Ordovician – Triassic
Order Cryptostomata – Ord – Permian
Order Fenestrata – Ordovician – Permian
Order Cyclostomata – Ordovician – Recent
Minor group in the Paleozoic, but survived to become on of three
living orders
Bryozoans -systematics
 Phylum Bryozoa
Class Stenolaemata – Ordovician – Recent
Order Trepostomata – Ordovician – Triassic
Order Cryptostomata – Ord – Permian
Order Fenestrata – Ordovician – Permian
Order Cyclostomata – Ordovician – Recent
Order Gymnolaemata – Ordovician – Recent
Minor group similar to the Cyclostomes
Bryozoans -systematics
 Phylum Bryozoa
Class Stenolaemata – Ordovician – Recent
Class Gymnolaemata – Ordovician – Recent
Bryozoans -systematics
 Phylum Bryozoa
Class Stenolaemata – Ordovician – Recent
Class Gymnolaemata – Ordovician – Recent
Most living forms belong to this class
Bryozoans -systematics
 Phylum Bryozoa
Class Stenolaemata – Ordovician – Recent
Class Gymnolaemata – Ordovician – Recent
Most living forms belong to this class. Have cylindrical or box-like
enclosures around the zooids. Each zooicium remains a fixed
size and discrete zooicia are added as the colony grows. Only
one of the two orders is geologically significant
Bryozoans -systematics
 Phylum Bryozoa
Class Stenolaemata – Ordovician – Recent
Class Gymnolaemata – Ordovician – Recent
Order Cheilostomata – Jurassic - Recent
Bryozoans -systematics
 Phylum Bryozoa
Class Stenolaemata – Ordovician – Recent
Class Gymnolaemata – Ordovician – Recent
Order Cheilostomata – Jurassic – Recent
Comprise the most diverse group of living bryozoans. Box-like
calcareous zooids have an operculum.
Bryozoans - ecology
 Bryozoans are filter feeders and tend to live in warm, clear
water.
Bryozoans - ecology
 Bryozoans are filter feeders and tend to live in warm, clear
water.
 They attach to a firm substrate and are common residents
of Paleozoic reef complexes.
Bryozoans - evolution
 Bryozoans evolve on the level of the colony rather than on
th e i n d i v i d u a l
Bryozoans - evolution
 Bryozoans evolve on the level of the colony rather than on
th e i n d i v i d u a l
 Evolutionary changes have been few, and the bryozoa, as
a group, have been stable over long periods of time.