Paleoiiithe Bryozoa & the Brachiopoda

7/27/2019 Paleoiiithe Bryozoa & the Brachiopoda

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The Bryozoa & The Brachiopoda

Paleontology Laboratory III



The Bryozoa

• The Bryozoa (moss animals) are a

geologically important group of smallanimals.

• Some superficially resemble corals.

• All bryozoans are colonial and most are

marine.

• Bryozoans are most abundant in temperate-

tropical waters that are not too turbid.

• They require a hard or firm substrate to

attach or encrust, and clear agitated water

from which they obtain their suspended food.



Bryozoa

•There are about 5000 living species, withseveral times that number of fossil

species.

•

Bryozoan colonies range from millimetersto meters in size, but the individuals that

make up the colonies are rarely larger

than a millimeter.

• Colonies may be mistaken for hydroids,

corals, or even seaweeds.



Bryozoa• Bryozoans are considered nuisances species by

some• Over 125 species are known to grow on the bottoms

of ships, causing drag and reducing the efficiencyand maneuverability of the fouled ships.

• Bryozoans may also foul pilings, piers, and docks.

• Certain freshwater species occasionally form great jellylike colonies so huge they clog public or industrial water intakes.

• Bryozoans produce a remarkable variety of chemicalcompounds, some of which may find uses inmedicine. – One compound produced by a common marine bryozoan, the drug

bryostatin 1, is currently under serious testing as an anti-cancer drug.



MORPHOLOGY



Classification & Range

• Phylum Bryozoa

– Class Stenolaemata (Ordovician-Recent)

• Order Trepostomata (Ordovician-Triassic)

• Order Fenestrata (Ordovician-Permian)

• Order Cyclostomata (Ordovician-Recent)

– Class Gymnolaemata (Ordovician-Recent)

•

Order Cheilostomata (Jurassic-Recent)



General Morphology and Ecology• As bryozoan individuals are quite small, they are

commonly observed under the microscope fromlongitudinal or transverse thin-sections.

• Bryozoans come in a variety of colonial growthhabits that can easily be observed without thin-

sections.• Like corals, the growth habit of bryozoans can

be classified as encrusting, massive or domal, or erect.

• Generally speaking, byozoan growth-habits area function of water energy similar to corals whichlived in level-bottom communities; – encrusting and massive forms are found in high-

energy environments

–

delicate branching and erect forms lived in quiteenvironments.



Encrusting



Massive or Domal



Erect



CLASSIFICATION

• Division of bryozoan groups is based on surficialmorphology, extra-zooidal structures, colonialgrowth habits, zooid morphology, presence of specialized zooids (e.g., maternal zooids), and

internal structures of the zooecium.• Colonial bryozoans come in two basic types:

– 1. Those with tightly packed zooecia which sharezooecium walls, they have multiple pores and a welldefined mature and immature region such as in the

trepostomes, cyclostomes, and the fenestrates. – 2. Those with moderately to loosely packed zooecia

usually encrusting one-zooecium-thick, andcommonly with frontal walls as typified by theCheilostomes



Class Stenolaemata• Ordovician-Recent

• The stenolaemate bryozoans quickly radiated in the early

Paleozoic and are very characteristic fossils of Paleozoicrocks, sometimes making substantial contributions to theformation of reefs, calcareous shales, and limestones.

• They included forms with robust skeletons

• There were also forms with delicate, branching fanlike

skeletons such as the fenestrates.• With the exception of one order of stenolaemates, the

Tubuliporata or Cyclostomata, all of these Paleozoicbryozoan lineages were severely impacted in the Permianextinction: cryptostomates disappeared at the end of the

Permian (245 million years ago), while a few other lineageslingered until the end of the Triassic, about 210 millionyears ago.

• Tubuliporate bryozoans have survived to this day, and infact underwent a remarkable radiation in the Cretaceous,but are no longer dominant today.



Order TREPOSTOMATA

• Trepostomes are characterized by long-curvedzooecia separated by thin walls.

• Each zooecium has mature and immature

regions.• Apertures of autopores are typically polygonal.

• Trepostomes can be differentiated from similar-looking cryptostomes by the thinner walls

between their zooecia.• The specimens are erect forms, whereas these

specimens are massive.



TREPOSTOMATA



Order CYCLOSTOMATA

• Cyclostomes are characterized by zooecia

that are simple tubes which lack partitions

(diaphragms) and have rounded apertures

and well defined mature and immatureregions.

• Most cyclostomes are encrusting forms

and some, can be quite small and veryloosely arranged creeping zooecia.



CYCLOSTOMATA



Order FENESTRATA

• Fenestrates are characterized by their zooariamorphology which form a mesh or net-like shapewith zooecia-bearing rods and open window-likeregions called fenstrules.

• Most fenestrates have considerable extra-zooidskeleton material which is necessary for support.

• This order is typified by erect, delicate

morphology.• Some fenestrates have considerable extra-

zooidal material such Archimedes which is anaxial rod that supports the net-like zooecia.



FENESTRATA



Class Gymnolaemata

• Ordovician-Recent

• Uncalcified gymnolaemates are known as fossilsalmost exclusively as distinctive borings incarbonate substrates such as shells.

•

Non-boring, non-calcified gymnolaemate bryozoansare extremely rare as fossils and known from theJurassic and Cretaceous only.

• Calcareous gymnolaemates did not appear in theoceans until the Cretaceous, during which time theydiversified rapidly from a very few species in theearly Cretaceous.

• By the end of the Cretaceous, there were over 100genera of gymnolaemates.

• They continued to diversify in the Cenozoic: todaythere are over 1000 genera, comprising the bulk of bryozoan diversity in today's seas.



Order CHEILOSTOMATA

• Cheilostomes are characterized by their

loosely packed colonies of box or coffin-

shaped zooecium.

• Many have round apertures and large

frontal areas on which brood pouches

which house the maternal zooids can often

be observed.



CHEILOSTOMATA



The Brachiopoda



Brachiopods• The brachiopods are a large group of solitary and

exclusively marine organisms with a very good geologichistory throughout most of the Phanerozoic and areamong the most successful benthic macroinvertebratesof the Paleozoic.

• They are typified by two mineralized valves whichenclose most of the animal.

• Brachiopods are filter feeders, which collect foodparticles on a ciliated organ called the lophophore.

• Brachiopods differ in many ways from bryozoans (in bothsoft and hard-part morphology), and are thus consideredby most workers as a separate but closely related

phylum.• However, one of the most distinguishing features of

brachiopods is the presence of a pedicle, a fleshy stalk-like structure that aids the animal in burrowing andmaintaining stability.



Lophophore

Pedicle



Morphology



BRACHIOPODA- Classification

Phylum Brachiopoda (Cambrian-Recent)

Class Inarticulata (Cambrian-Recent)

Class Articulata (Cambrian-Recent)

Order Orthida (Cambrian-Permian)

Order Strophomenida (Ordovician-Jurassic)

Order Pentamerida (Cambrian-Devonian)

Order Rhynchonellida (Ordovician-Recent)

Order Spiriferida (Ordovician-Jurassic)

Order Terebratulida (Devonian-Recent

Cl I ti l t



Class Inarticulata• Inarticulate brachiopods do not posses teeth and

sockets, nor do they have clearly defined diductor

muscles.• Instead, the valves are held together by a complex of

adductor muscles.

• Although some inarticulates construct their valves of calcite, most have shells of a mineral composition of

chitin and calcium phosphate which can be recognizedby its shiny, enamel-like luster.

• Inarticulate brachiopods usually lack surficialornamentation except growth lines.

• The classic example of the inarticulates belong to the

order Lingulida.• The linguloids are small, biconvex, with usually oval or

circular outlines.

• This order has quite a long geologic history with somegenera (and possible species) remaining relatively

unchanged since the Cambrian



Class Inarticulata

• The only brachiopods to support a minor commercial fishery, lingulate brachiopods arealso among the oldest of all brachiopods, andthe most morphologically conservative, having

lasted since the Cambrian with very little changein shape.

• The preserved specimen of a living lingulate,Lingula, shows the typical tongue-shaped shell(hence the name Lingulata, from the Latin wordfor "tongue") with a long stalk, or pedicle, withwhich the animal burrows into sandy or muddysediments.

http://www.ucmp.berkeley.edu/cambrian/camb.html

http://www.ucmp.berkeley.edu/cambrian/camb.html



Unlike the shells of almost all other marine organisms, which

are typically made of calcium carbonate, the shells of lingulidsare composed of calcium phosphate. The rest of the body is

fairly typical of brachiopods in general, but the pedicle is quite

long. This facilitates burrowing; extant Lingula is typically found

burrowed in soft muddy sediments with only the valve edges

protruding.



Class Articulata

• Articulate brachiopods differ from inarticulates inthat the articulates posses teeth and socketsand mineralized lophophore supports.

• The classification of articulate orders and

suborders depends primarily upon characters of the hinge and beak areas (including hingelength, teeth and sockets, pedicle opening,etc....) and perhaps more importantly, althoughmore difficult to asses, the nature of the

lophophore support.• Other features (such as the shell microstructure,

surface ornamentation) sometimes are quitediagnostic of several orders and suborders of

brachiopods.



Order Orthida

• Shells of orthids are typically strophic(having an elongated hinge line)

• The shape is generally semi- or sub-

circular in outline.• Valve convexity is usually unequally

biconvex with a slightly inflated pedicle

valve.• Orthids are typically covered with fine

diverging radial costae.



Orthida

Platystrophia

Late Ordovician



Strophomenida

• The Strophomenida were the largest order of

brachiopods, with about 400 genera.

• They were also by far the most

morphologically diverse group, and includedsome very unusual forms, as well as more

"normal" forms.

• Strophomenids first appeared in the

Ordovician and persisted until the middle

Jurassic.



Strophomenida

• Strophomenids may be identified by their supra-apicallylocated pedicle foramen, at least in young shells.

• Adult strophomenids lacked an open pedicle foramen, andusually lived attached to the bottom or to other objects by thepedicle valve.

• One group of strophomenids, theproductids, were

characterized by very long spines extending from the shell.• These are thought to have functioned as a sort of "snowshoe,"

supporting and stabilizing the organism on soft muds.

• Other strophomenids were attached to the bottom by a cone-shaped pedicle valve, with the upper valve covering the conelike a pot lid.

• The unusual brachiopod Pror ichthofenia from the Permian of Texas is one of these unusual conical forms.

• This shape is convergent on that of other attached organisms,such as Paleozoic rugose corals and living scleractinian corals,and it is though that, like corals, some strophomenids borephotosynthetic algae inside their tissues that helped to supply

them with food.

http://www.ucmp.berkeley.edu/brachiopoda/prorichthofenia.gif




Pror ichthofenia Rugose Coral





Order Pentamerida

• Shells of pentamerids are generally biconvex.• Pentamerids are typically ovoid, circular,

triangular, or more commonly pentameral inoutline.

• The interior of the shell is typified by a prominentmedial ridge or septa in the brachial and/or pedicle valve.

• Also diagnostic of pentamerids is a spoon

shaped structure modified from plates in thepedicle valve called the spondylium whichsupported muscle tissues



Pentamerida



Pentamerids grew to sizes of over 10 cm, and they

represent one of the largest types of dwellers withinSilurian reefs. A thickened beak area served as a

weight to stabilize the shell in the sediment, and

there was no fixed attachment. Pentamerid

brachiopods often lived as clumps of individuals.



Rhynchonellida

• Rhynchonellids look a bit like little nuts.

• Their hinges come to a point, a conditionpaleontologists call non-strophic.

• They are often ridged.

• The commisure, the line between the two valves or shells, is zig-zagged, as can be seen in thesomewhat unusual asymmetric rhynchonellidRhactorhynchia .

• The earliest fossil rhynchonellids are from theOrdovician period.

• During the Mesozoic Era, rhynchonellids were themost abundant brachiopods.

• A few species still exist today.

http://www.ucmp.berkeley.edu/brachiopoda/rhactorhynchia.jpg




Rhynchonellida

Rhactorhynchia

Spiriferida





Spiriferida

• Spiriferids are easy to identify.

• They often have an extended hingeline so wide they look winged.

• Other prominent characters are thefold and the sulcus that you can

see.• The feature that gives the spiriferids

their name ("spiral-bearers") is theinternal support for the lophophore;this support, which is oftenpreserved in fossils, is a thin stripof calcareous material that istypically coiled tightly within theshell.

• Fossil spiriferids first appear in the

http://www.ucmp.berkeley.edu/glossary/gloss7/lophophore.html

http://www.ucmp.berkeley.edu/glossary/gloss7/lophophore.html



Fossil spiriferids first appear in the

Ordovician period.

• They were extremely diverse during the

Devonian period and later went extinct

during the Jurassic period.

• Some fossil brachiopods make

spectacular finds, replaced by pyrite



Terebratulida

• Most living brachiopod, arerepresentative of the group;terebratulids.

• Terebratulids first appear as fossils inthe Devonian.

• Terebratulids are responsible for thename of "lamp shells" for brachiopods;their shells resemble ancient oil lamps,with the pedicle foramen resembling awick.



Terebratulida



Paleoecology • All brachiopods are filter feeding, sessile (non-

mobile) bottom dwellers.• They are exclusively marine, but inhabit a variety

of bottom environments at various depths andlatitudes.

• Brachiopods are either free-living or rooted bytheir pedicle to the substrate.

• During life, they can be oriented either vertically,inclined, or horizontally to the substrate.

• Typically brachiopods oriented vertically duringlife will have equally biconvex shells, whereasinclined and horizontally oriented ones will beunequal inflation being plano-convex, concavo-convex



Infaunal

• Living totally buried within the sediment.

Brachiopods living this way are oriented

posterior downward, and are usually

stabilized by their downward projectingpedicle.

• Lingulid inarticulates are among the only

brachiopods to exploit this infaunalenvironment



The pedicle is quite long. This facilitates burrowing; extant

Lingula is typically found burrowed in soft muddy sedimentswith only the valve edges protruding.



Semi-Infaunal

• In this position, the animal is oriented

vertically (posterior downward) and is only

partially buried in the sediment; they may

or may not be attached by their pedicle.



Reclining

• In this position, the animal is in effect floatinghorizontally on (or partially within) the sedimentwith the pedicle valve as the lower valve.

• Generally, reclining brachiopods have a

concavo-convex or plano-convex shape.• Other modifications include large surface area

and spines to help the critter float.

• The pedicle opening is usually not present.

•Note that one of the specimens also bearsattachment points for spines, which served as anadditional adaptation for reclining in softsediments.



Epifaunal

• In this position, the brachiopod is attached

either to the sediment or other object (e.g.,

marine plants) by their pedicle.

Paleoiiithe Bryozoa & the Brachiopoda

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