Elasmobranchii

Its related with the stream of Biology .
This is all about the Cartilaginous fish - easy explanation and classification.
Also include fundamental characterstics of Pisces
Which is a class of Superclass Pisces.

1. GENERAL ACCOUNT OF ELASMOBRANCHII AND HOLOCEPHALI Submitted By- Nilesh Khandelwal MSc.Zoology SEM III Department of Zoology

2. GENERAL CHRACTERS OF PISCES Cold blooded and exclusively aquatic. Gill slits covered or naked . Lateral line system present Exoskeleton in form of scales Body – spindle shaped or streamlined. Paired fin present Endoskeleton- bony or cartilaginous. Kidney- mesonephric Cranial nerves-10 pairs Heart 2 chambered Internal fertilization Separate sexes Cleavage incomplete and direct development.

3. CLASSIFICATION OF PISCES Fishes have been classified in different ways from time to time. Some important classification are- Berg’s classification,1940(7 classes) Romer’s classification,1959(2 classes) Parker and Haswell,1960 (3 classes)

4. BERG’S CLASSIFICATION CLASS SUBCLASS STATUS PTERICHTHYS EXTINCT COCCOSTEI EXTINCT ACANTHODI EXTINCT ELASMOBRANCHI HOLOCEPHALI DIPNOI TELEOSTOMI CROSSOPTERGI I ACTINOPTERGI I

5. ROMERS CLASSIFICATION CLASS SUB-CLASS Chondrichthyes ELASMOBRANCHI HOLOCEPHALI Osteiochthyes DIPNOI TELEOSTOMI

6. PARKER AND HASWELL CLASSIFICATION CLASS STATUS PLASMOBRANCHII EXTINCT CHONDRICHTHYES OSTEICHTHYES

7. ELASMOBRANCHII elasmo= plate, branchii= plate Also called as chondricthyes Marine and predacious in nature. The endoskeleton is entirely cartilaginous without true bones. Placoid scales form the exoskeleton . Pelvic fin modified into claspers. Caudal fin is heterocercal. Gills are lamelliform. Gill slits are 4 to 7 pairs without operculum.

8. Ventral mouth present. Teeth are modified placoid scale. No air bladder or lungs present. Cloaca present. Oviparous / ovoviviparous. Heart 2 chambered- venous heart Ureotelic excretion Direct development.

9. Elasmobranchii have 2 sub-classes Subclass Order Examples SELACHII SQUALIFORMES SHARKS RAJIFORMES SKATES HOLOCEPHALI RAT FISHES

10. SUB-CLASS -SELACHII selachos (Greek) = sharks Multiple gill slits on either side protected by skin flaps. A spiracle behind each eye. Cloaca present.

11. ORDER-SQUALIFORMES(PLEUROTREMATA) Pleuro- Lateral;trema -opening Spindle shaped body Gill slits lateral Pectoral fins moderate,constricted at base. Heterocercal tail Examples- Scoliodon,Chiloscyllium,Rhineodon

12. True sharks Sphyrna Zebra Shark Heptanchus Mustelus

13. ORDER-RAJIFORMES OR HYPOTREMATA Hypo-below;trema-opening Body depressed,dorsoventrally flattened Gill slits ventral,5pairs. Pectoral fins enlarged, fused to sides of head and body. Spiracles large,highly functional. Examples:Skates and Rays Trygon,Torpedo,Myliobatis,Rhinobatus.

14. SKATES Common Raja Pacific white skate Dipturus Ocellate spot skate

15. RAYS Torpedo Trygon Rhinobatus Myliobatis

16. SUB-CLASS HOLOCEPHALI Holo-entire ; cephale-head Single gill opening on either side coverd by a fleshy operculum. No spiracles,cloaca and scales. Jaws with toothed plates. Single nasal opening Lateral line system with open groove. Examples-Rat Fishes or Chimaeras Hydrolagu s

17. Chimaera Hetrolagus

18. THANK YOU