CNIDARIACNIDARIAPhylum:Phylum:

Cnidaria:Cnidaria: (formerly called Coelenterata) (formerly called Coelenterata)Class:Class:

Anthozoa:Anthozoa: (corals) (corals)Hydrozoa:Hydrozoa: (hydroids) (hydroids)Scyphozoa:Scyphozoa: (jellyfish) (jellyfish)

Sub-Classes:Sub-Classes:Zoantharia:Zoantharia:

RugosaRugosa (extinct)(extinct)TabulataTabulata (extinct) (extinct)ScleractinaScleractina (reef building, still exist part of the (reef building, still exist part of the Zoantharia).Zoantharia).

The The polypspolyps are are solitarysolitary or or colonialcolonial..

The soft parts are divided The soft parts are divided into 6, 8 or more.into 6, 8 or more.

Often have a Often have a bilateral bilateral symmetry.symmetry.

MarineMarine..

ANTHOZOAN MORPHOLOGY:ANTHOZOAN MORPHOLOGY: Corals are usually sack Corals are usually sack

shaped widest at the top shaped widest at the top which contained the which contained the MOUTH MOUTH narrowing at the narrowing at the base where it was base where it was attached.attached.

Page Page 101 101 Copy Copy Fig. 63aFig. 63a.. Draw Draw c and hc and h on page on page 103103

for a typical solitary coral.for a typical solitary coral. The body structure is The body structure is

simple with a hard calcite simple with a hard calcite outer layer and an inner outer layer and an inner body cavity.body cavity.

SOFT PARTS:SOFT PARTS: The soft parts are similar in all The soft parts are similar in all

the subclasses.the subclasses. Page Page 114 Black Fig. 72a and 114 Black Fig. 72a and

bb (draw). (draw). The body cavity is divided into The body cavity is divided into

small segments bysmall segments by RADIAL RADIAL MESENTERIESMESENTERIES (partitions) (partitions) which give it stability and which give it stability and strength and provide more strength and provide more efficient feeding.efficient feeding.

Outer Layer = Outer Layer = ECTODERMECTODERM Inner Layer = Inner Layer = ENDODERMENDODERM The inner body cavity = The inner body cavity =

COELENTERON (ENTERON)COELENTERON (ENTERON)

Mesenteries Mesenteries help spread the help spread the surface area of the coelenteron surface area of the coelenteron and therefore help digestion of and therefore help digestion of food.food.

The The MOUTH MOUTH is usually towards is usually towards the centre and has a number of the centre and has a number of functions:functions:

1.1. Takes in food.Takes in food.2.2. Allows discharge of waste.Allows discharge of waste.3.3. Discharge of larvae.Discharge of larvae. The mouth is surrounded by The mouth is surrounded by

retractable tentaclesretractable tentacles, which , which have stinging organs on them.have stinging organs on them.

Some corals show a Some corals show a bilateral bilateral symmetrysymmetry but more commonly but more commonly show show radial symmetryradial symmetry with parts with parts of the body repeated in the of the body repeated in the coelenteron around the mouth.coelenteron around the mouth.

Middle Ordovician - Middle Ordovician - PermianPermian..

Occur as Occur as solitarysolitary or or compoundcompound forms. forms.

SOLITARY RUGOSE SOLITARY RUGOSE CORALS:CORALS:

CoraliteCoraliteis conical in shape.is conical in shape. The skeleton grew upwards The skeleton grew upwards

from a narrow base.from a narrow base. The whole structure can be The whole structure can be

straight or curved (straight or curved (horn horn shapedshaped).).

CALICE CALICE or the top of the or the top of the body appears like a body appears like a depression and in this depression and in this can be seen a central can be seen a central region called the region called the AXIAL AXIAL REGION.REGION.

The ends of the The ends of the SEPTASEPTA can also be seen can also be seen sometimes.sometimes.

A A COLUMELLACOLUMELLA may be may be present in the centre present in the centre (rod like)(rod like)

Colonial/Compound Rugose Colonial/Compound Rugose CoralsCorals

In colonial rugose In colonial rugose corals there are often a corals there are often a large number of septa.large number of septa.

TABULAE:TABULAE: These These represent former levels represent former levels of the calice floor, of the calice floor, secreted by the polyp secreted by the polyp to seal off the lower to seal off the lower area of the area of the corallumcorallum..

They are best seen if They are best seen if longitudinal sections longitudinal sections are cut.are cut.

Colonial/Compound Rugose Colonial/Compound Rugose CoralsCorals

They are made up of varying They are made up of varying numbers of individuals each called numbers of individuals each called a a corallitecorallite. . Fig. 63 page 101 (OHP).Fig. 63 page 101 (OHP).

They are subdivided based on the They are subdivided based on the relationship between the corallites:relationship between the corallites:

FASCICULATE:FASCICULATE: The individuals are The individuals are not closely not closely

touchingtouching.. Fasciculate corals can be further Fasciculate corals can be further

sub divided:sub divided:DENDROID:DENDROID: They They branchbranch irregularly. irregularly.PHACELOID:PHACELOID: If the corallites are If the corallites are parallel parallel to each to each

other.other.

Colonial/Compound Rugose Colonial/Compound Rugose CoralsCorals

MASSIVE:MASSIVE: All the corallites are All the corallites are in in

contactcontact.. These are also further sub These are also further sub

divided:divided:

CERIOID:CERIOID: Polygonal corallites in Polygonal corallites in

cross section and they cross section and they have a have a clear dividing wallclear dividing wall..

ASTRAEOIDASTRAEOID:: The The walls are absentwalls are absent..

SessileSessile apart from when in apart from when in larval stagelarval stage..

BenthonicBenthonic and and fixedfixed.. lived in warm (lived in warm (22 - 29ºC 22 - 29ºC

ideally 25ºCideally 25ºC) tropical.) tropical. Shallow seas ideally Shallow seas ideally <25 m<25 m

continental shelf.continental shelf. They like They like clear waterclear water with little with little

sediment.sediment. Well Well oxygenated, high energyoxygenated, high energy.. Typically found in carbonate Typically found in carbonate

rocks especially in the rocks especially in the Carboniferous. Carboniferous.

Mode of life and Mode of life and palaeoenvironment (Index palaeoenvironment (Index

Fossil)Fossil)

Appear in the middle of Appear in the middle of the the OrdovicianOrdovician but are not but are not common until the common until the Silurian.Silurian.

Throughout the rest of the Throughout the rest of the PalaeozoicPalaeozoic their numbers their numbers increased.increased.

They reached their They reached their maximummaximum in the in the Lower Lower CarboniferousCarboniferous and then and then gradually gradually declined declined and and disappeared in the disappeared in the Permian extinctionPermian extinction..

These are These are extinct extinct compound coralscompound corals..

They have slender They have slender corallitescorallites, which are , which are crossed transversely by crossed transversely by tabulae.tabulae.

They have a calcareous They have a calcareous skeleton with usually small skeleton with usually small individual corallites individual corallites although the whole colony although the whole colony can be large.can be large.

Shape:Shape: either either fasciculatefasciculate (no contact) or (no contact) or massivemassive..

TheThe fasciculate fasciculate forms can forms can branch branch irregularlyirregularly..

In others the corallites are joined In others the corallites are joined laterally to form a laterally to form a chain likechain like structure structure approximately one corallite wide.approximately one corallite wide.

The The calice is usually smallcalice is usually small being a being a few mm in diameter and varying in few mm in diameter and varying in shape : round, oval or polygonal.shape : round, oval or polygonal.

The The septa are not always presentsepta are not always present but but number about 12 if they are present number about 12 if they are present and they are similar in size and and they are similar in size and shape.shape.

Tabulae are very numerousTabulae are very numerous and and occur horizontally although some occur horizontally although some appear domed.appear domed.

Mural pores:Mural pores: small holes that connect small holes that connect the corallitethe corallite

Tabulate Corals To KnowTabulate Corals To Know FavositesFavosites:: Upper Ordovician - Devonian.Upper Ordovician - Devonian. Draw:Draw: HalysitesHalysites:: Ordovician to Silurian.Ordovician to Silurian. Draw:Draw:

FAVOSITES:FAVOSITES: Massive corallumMassive corallum, often a , often a

hemispherehemisphere shape. shape. The whole colony is usually fairly The whole colony is usually fairly

smallsmall, maximum being 10 cm , maximum being 10 cm across, rarely larger.across, rarely larger.

CerioidCerioid (polygonal) corallites which (polygonal) corallites which are often quite long.are often quite long.

Each calice is small: Each calice is small: 2 - 3 mm2 - 3 mm in in diameter.diameter.

The The septa are often absentsepta are often absent, if , if present they form ridges.present they form ridges.

TabulaeTabulae are numerous and evenly are numerous and evenly spaced.spaced.

Most important in the Most important in the SilurianSilurian..

HALYSITES:HALYSITES:

Phaceloid corallumPhaceloid corallum giving an giving an almost chain like appearance as almost chain like appearance as corallites can be joined together corallites can be joined together on two or three sides to form a on two or three sides to form a branching structure.branching structure.

Commonly called “Commonly called “chained chained coralcoral”.”.

Septa are usually absentSepta are usually absent and and the tabulae are horizontal.the tabulae are horizontal.

Middle Ordovician to Permian Middle Ordovician to Permian extinctionextinction..

Most abundant in the Most abundant in the Silurian and Silurian and DevonianDevonian, then through the Upper , then through the Upper Palaeozoic the numbers decreased and Palaeozoic the numbers decreased and died out in the died out in the Permian extinctionPermian extinction..

Most common in carbonate rocks e.g. Most common in carbonate rocks e.g. limestonelimestone, rarely found in muddy , rarely found in muddy sediments.sediments.

During the Silurian and Devonian During the Silurian and Devonian important important reef formationreef formation and during this and during this time they were more numerous than time they were more numerous than rugose corals.rugose corals.

Silurian:Silurian: Favosites Favosites and and Halysites Halysites common.common.

Devonian:Devonian: FavositesFavosites still common. still common.

Solitary or Solitary or compound corals.compound corals.

Some still exist.Some still exist.

Draw Draw figs 73 f and h Black figs 73 f and h Black page 116page 116..

Their originally Their originally aragonitic aragonitic skeletons have skeletons have dissepiments, tabulae, and dissepiments, tabulae, and septasepta just as in the just as in the rugosa.rugosa.

Although there are Although there are superficial similarities, superficial similarities, scleractinian corals differ scleractinian corals differ from rugosa corals by their from rugosa corals by their skeletal skeletal mineralogymineralogy and by and by their method of their method of septal septal insertioninsertion during growth. during growth.

Scleractinian corals also have Scleractinian corals also have six primary septasix primary septa, but in , but in contrast to rugose corals, contrast to rugose corals, subsequent septa are added subsequent septa are added in in all sixall six of the resulting spaces. of the resulting spaces.

An important distinction An important distinction between the two orders is that between the two orders is that for the Scleractinia the septa for the Scleractinia the septa are inserted between every two are inserted between every two pre-existing septa in later pre-existing septa in later growth stages.growth stages.

Therefore have a repeated Therefore have a repeated radial symmetryradial symmetry and so and so different from the Rugosa.different from the Rugosa.

Adjacent polyps can be Adjacent polyps can be attached or attached or connected connected together via common soft together via common soft tissuetissue..

They resemble sea They resemble sea anemones.anemones.

The corallum of the The corallum of the solitarysolitary corals is usually corals is usually conical or cylindricalconical or cylindrical..

In In compound compound types there is types there is a much a much wider range of wider range of sizes and shapessizes and shapes..

Use the same terminology Use the same terminology as used in rugose corals.as used in rugose corals.

Middle Middle Triassic to Recent.Triassic to Recent. Most important in the Most important in the JurassicJurassic.. Not very important in the Not very important in the

Cretaceous but can be found in Cretaceous but can be found in the Chalk in particular solitary the Chalk in particular solitary forms.forms.

In the Tertiary there are a few In the Tertiary there are a few reef-building forms and more reef-building forms and more recently in the Quaternary cup recently in the Quaternary cup like corals are more common.like corals are more common.

In theIn the present present they form they form important important reef building animalsreef building animals in in the the tropics and sub tropicstropics and sub tropics around ocean islands and east around ocean islands and east coasts of large landmasses.coasts of large landmasses.