1 / 24

CNIDARIA

CNIDARIA. Phylum: Cnidaria: (formerly called Coelenterata) Class: Anthozoa: (corals) Hydrozoa: (hydroids) Scyphozoa: (jellyfish) Sub-Classes: Zoantharia: Rugosa (extinct) Tabulata (extinct) Scleractina (reef building, still exist part of the Zoantharia). CLASS : ANTHOZOA (CORALS).

emery-burt
Download Presentation

CNIDARIA

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. CNIDARIA Phylum: Cnidaria: (formerly called Coelenterata) Class: Anthozoa: (corals) Hydrozoa: (hydroids) Scyphozoa: (jellyfish) Sub-Classes: Zoantharia: Rugosa(extinct) Tabulata (extinct) Scleractina (reef building, still exist part of the Zoantharia).

  2. CLASS : ANTHOZOA (CORALS) • The polyps are solitary or colonial. • The soft parts are divided into 6, 8 or more. • Often have a bilateral symmetry. • Marine.

  3. ANTHOZOAN MORPHOLOGY: • Corals are usually sack shaped widest at the top which contained the MOUTH narrowing at the base where it was attached. • Page 101 Copy Fig. 63a. • Draw c and h on page 103 for a typical solitary coral. • The body structure is simple with a hard calcite outer layer and an inner body cavity.

  4. SOFT PARTS: • The soft parts are similar in all the subclasses. • Page 114 Black Fig. 72a and b (draw). • The body cavity is divided into small segments byRADIAL MESENTERIES (partitions) which give it stability and strength and provide more efficient feeding. • Outer Layer = ECTODERM • Inner Layer = ENDODERM • The inner body cavity = COELENTERON (ENTERON)

  5. Mesenteries help spread the surface area of the coelenteron and therefore help digestion of food. • The MOUTH is usually towards the centre and has a number of functions: • Takes in food. • Allows discharge of waste. • Discharge of larvae. • The mouth is surrounded by retractable tentacles, which have stinging organs on them. • Some corals show a bilateral symmetry but more commonly show radial symmetry with parts of the body repeated in the coelenteron around the mouth.

  6. SUBCLASS: RUGOSA • Middle Ordovician - Permian. • Occur as solitary or compound forms. SOLITARY RUGOSE CORALS: • Coraliteis conical in shape. • The skeleton grew upwards from a narrow base. • The whole structure can be straight or curved (horn shaped).

  7. SUBCLASS: RUGOSA • CALICE or the top of the body appears like a depression and in this can be seen a central region called the AXIAL REGION. • The ends of the SEPTA can also be seen sometimes. • A COLUMELLA may be present in the centre (rod like)

  8. Colonial/Compound Rugose Corals • In colonial rugose corals there are often a large number of septa. • TABULAE: These represent former levels of the calice floor, secreted by the polyp to seal off the lower area of the corallum. • They are best seen if longitudinal sections are cut.

  9. Colonial/Compound Rugose Corals • They are made up of varying numbers of individuals each called a corallite. Fig. 63 page 101 (OHP). • They are subdivided based on the relationship between the corallites: FASCICULATE: • The individuals are not closely touching. • Fasciculate corals can be further sub divided: DENDROID: • They branch irregularly. PHACELOID: • If the corallites are parallel to each other.

  10. Colonial/Compound Rugose Corals MASSIVE: • All the corallites are in contact. • These are also further sub divided: CERIOID: • Polygonal corallites in cross section and they have a clear dividing wall. ASTRAEOID: • The walls are absent.

  11. Mode of life and palaeoenvironment (Index Fossil) • Sessile apart from when in larval stage. • Benthonic and fixed. • lived in warm (22 - 29ºC ideally 25ºC) tropical. • Shallow seas ideally <25 m continental shelf. • They like clear water with little sediment. • Well oxygenated, high energy. • Typically found in carbonate rocks especially in the Carboniferous.

  12. GEOLOGICAL HISTORY: • Appear in the middle of the Ordovician but are not common until the Silurian. • Throughout the rest of the Palaeozoic their numbers increased. • They reached their maximum in the Lower Carboniferous and then gradually declined and disappeared in the Permian extinction.

  13. SUBCLASS: TABULATA: • These are extinct compound corals. • They have slender corallites, which are crossed transversely by tabulae. • They have a calcareous skeleton with usually small individual corallites although the whole colony can be large. • Shape: either fasciculate (no contact) or massive.

  14. The fasciculate forms can branch irregularly. • In others the corallites are joined laterally to form a chain like structure approximately one corallite wide. • The calice is usually small being a few mm in diameter and varying in shape : round, oval or polygonal. • The septa are not always present but number about 12 if they are present and they are similar in size and shape. • Tabulae are very numerous and occur horizontally although some appear domed. • Mural pores: small holes that connect the corallite

  15. Tabulate Corals To Know • Favosites: • Upper Ordovician - Devonian. • Draw: • Halysites: • Ordovician to Silurian. • Draw:

  16. FAVOSITES: • Massive corallum, often a hemisphere shape. • The whole colony is usually fairly small, maximum being 10 cm across, rarely larger. • Cerioid (polygonal) corallites which are often quite long. • Each calice is small: 2 - 3 mm in diameter. • The septa are often absent, if present they form ridges. • Tabulae are numerous and evenly spaced. • Most important in the Silurian.

  17. HALYSITES: • Phaceloid corallum giving an almost chain like appearance as corallites can be joined together on two or three sides to form a branching structure. • Commonly called “chained coral”. • Septa are usually absent and the tabulae are horizontal.

  18. GEOLOGICAL HISTORY: • Middle Ordovician to Permian extinction. • Most abundant in the Silurian and Devonian, then through the Upper Palaeozoic the numbers decreased and died out in the Permian extinction. • Most common in carbonate rocks e.g. limestone, rarely found in muddy sediments. • During the Silurian and Devonian important reef formation and during this time they were more numerous than rugose corals. • Silurian: Favosites and Halysites common. • Devonian:Favosites still common.

  19. ORDER: SCLERACTINIA: • Solitary or compound corals. • Some still exist.

  20. ORDER: SCLERACTINIA: • Draw figs 73 f and h Black page 116. • Their originally aragonitic skeletons have dissepiments, tabulae, and septa just as in the rugosa. • Although there are superficial similarities, scleractinian corals differ from rugosa corals by their skeletal mineralogy and by their method of septal insertion during growth.

  21. ORDER: SCLERACTINIA: • Scleractinian corals also have six primary septa, but in contrast to rugose corals, subsequent septa are added in all six of the resulting spaces. • An important distinction between the two orders is that for the Scleractinia the septa are inserted between every two pre-existing septa in later growth stages. • Therefore have a repeated radial symmetry and so different from the Rugosa.

  22. ORDER: SCLERACTINIA: • Adjacent polyps can be attached or connected together via common soft tissue. • They resemble sea anemones. • The corallum of the solitary corals is usually conical or cylindrical. • In compound types there is a much wider range of sizes and shapes. • Use the same terminology as used in rugose corals.

  23. GEOLOGICAL HISTORY: • Middle Triassic to Recent. • Most important in the Jurassic. • Not very important in the Cretaceous but can be found in the Chalk in particular solitary forms. • In the Tertiary there are a few reef-building forms and more recently in the Quaternary cup like corals are more common. • In the present they form important reef building animals in the tropics and sub tropics around ocean islands and east coasts of large landmasses.

More Related