Skeltal features and classification of Class Anthozoa and brief explanation of the Orders comiing under them.

1. PHYLUM

2. Group of living and extinct invertebrate.
It includes the simplest of many celled animals
( Metazoa).
It is exclusively aquatic and majority are marine.
Eg : Jelly fish , fresh water hydra.
All are soft bodied and reef building corals
which secrete calcareous skeleton.
Both solitary and colonial .

3. FRESH WATER HYDRA JELLY FISH

4. Living Coelenterates are two types,
1. Polyps /Polypoid
•Tabular or sac like body.
•Closed at bottom.
•Open at top with tentacles surrounding the
opening.
•Opening is called Mouth or Oral pore.
•Presence of digestive cavity.

5. 2 . Medusae
•Fringed umbrella with tentacles hanging
downword.
•Mouth is located in the central position of short
tube called Manubrium.

6. Structure
Outer layer – Ectoderm /epidermis
Inner layer – Endoderm /gastroderm.
Intermediate layer –Mesoderm.
Central cavity –gastrovascular cavity.
Mouth – intake of food, discharge of waste and
larva.
Stinging cells – Nematocyts(hold the prey)
Absence of blood and nervous system.
Both sexual and asexual .
Radial symmetry.
Common in warm shallow sea.

7. CLASSIFICATION

9. ANTHOZOA
Exclusively marine mostly sessile.
Radial or bilateral symmetry.
Flower like upper surface –oral disc.
Either solitary or colonial.
Both sexual and asexual reproduction.
Medusoid stage is absent..
Dominent in PHANEROZOIC EON.

10. SKELETAL FEATURES
Massive calcareous exoskeleton secreted
by ectodermal cells.
Coral skeleton consist of three element;
1. The basal plate :
First formed skeletal structure.
2. The epitheca :
Outer wall of theca.
3. The septa :
Help to maintain the shape of the polyp.

11. CLASSIFICATION
Class Anthozoa is divided into two subclass ;
1.Alcyonaria
2.Zoantharia
There are three orders ;
1.Order Rugosa
2.Order Tabulata
3.Order Scleractina

13. ORDER RUGOSA (Tetracorallia)
•It is large and extinct group of solitary and colonial
corals.
•Preserved in calcareous rock of PALAEOZOIC ERA.
EXTERNAL FEATURES
In rugose corals the corallum is conical and may
be straight or curved.
The curved corallum is resembles to horn and it is
called Horn corals.

14. SHAPE
Patellate –extremely low conical
Pyramidal –pyramid with angular edge
Scolicoidal-worm like cylindrical corallite
Button corals- botton shaped
Turbinate-steep conical

15. INTERNAL STRUCTURE
The interior of a corallite consisting of the entire space
enclosed by the epitheca is termed the THECARIUM.
SEPTA
The cheif vertical skeletal element.
First internal structure.
It may be straight , wavy,and zig –zag.
Two type of septa,
1.Majorsepta-longer ones
2.Minor septa-shorter ones

16. TABULAE
Transverse skeletal element found in corals
beneath the floor of Calyx.
DISSEPIMENTS
Corals in which minor septa are developed generally
characterised by a Peripheral zone in which there are
innumerable small convex plate . The convex surface of
these plate face inward and upward these are termed as
Dissepiment
COMPOUND CORALS (corallum)
It is the skeleton secreted by a collonial coral.

18. GEOLOGICAL HISTORY
It is found in middle ordovician to upper
permian.

19. ORDER TABULATA
Extinct group
Colonial corals
Important reef builders of the palaeozoic seas.
Two major type of tabulate corals;
1.Schizocoralla
New individuals are introduced by fission.
2.Thallocoralls
New individuals are formed by budding from
the sides of corallite.

20. ECOLOGY
They are important frame work builders in
Palaeozoic rims.
GEOLOGICAL HISTORY
First appeared in the early ordovician to
post permian.

22. ORDER SCLERACTINIA (Hexacorallia)
Solitary and colonial
Important reef builders of modern sea.
Dominent reef builders of mesozoic and cenozoic.
STRUCTURE
Soft basal disc , cylindrical body , tentacles arround
the oval mouth.
SKELETAL FEATURES
Solitary and colonial
Calcareous exoskeleton

23. *Other skeletal elements
1. Basal plate
 Secreted below the soft basal disc
 It get thickened when corallum grows.
2. Septa
 Dominent structural element.
 It is made up of fibrous , aragonitic structural unit
secreted by cells called calicobla.
3. Coenosteum
Space between adjacent corallites in compound corallum
is often filled with vescicular tissue called coenosteum.

24. 4. Costae
Septa project beyond the wall of a Corallite.
These prominent external Ribs secreted by the edge zone
are called Costae.
5. Pali
Vertical lamellae lying near the axis of corallite.
6. Columellae
Several type of axial structure found in the axial region
of corallite.
7. Synapticulae
Stumpy rods lie at right angles to the septa connecting
to theopposite face of septa.

26. FOSSIL OF JELLY FISH
JELLY FISH

27. Presented by,
Ameena Asharaf
B.Sc Geology
University college, Trivandrum
27 October 2017