Difference Cartilaginous and Bony Fishes

Cartilaginous Fishes

• Cartilaginous fishes are mostly marine.
• The mouth of cartilaginous fishes is ventral.
• The external nares are ventral.
• The scales of cartilaginous fishes are Placoid.
• In cartilaginous fishes, operculum is absent except chimaera.
• Caudal fins are heterocercal (asymmetrical).
• In cartilaginous fishes, cloaca are present except chimaera.
• Endoskeleton is cartilaginous.
• Sprial valve is present in the intestine of cartilaginous fishes.
• Cartilaginous fishes have 5-7 pairs of gills.
• Swimbladder (air bladder) is absent in cartilaginous fishes.
• Excretory matter of cartilaginous fishes is Urea.

Difference Bony Fishes

• Bony fishes are mostly marine and fresh water.
• The mouth of bony fishes is anterior.
• The external nares are dorsal.
• The scales of bony fishes are genoid, cycloid and ctenoid.
• In bony fishes, operculum is present
• Caudal fins are usually homocercal (symmetrical).
• In bony fishes, cloaca is absent.
• Endoskeleton is partly or wholly bony.
• Sprial valve is usually absent in intestine of bony fishes.
• Bony fishes have 4 pairs of gills. 
• Swimbladder (air bladder) is present in bony fishes. 
• Excretory matter of bony fishes is ammonia.

Characteristics	Chondrichthyes (Cartilaginous fish)	Osteichthyes (Bony fish)
Habitat	Mainly marine	Marine as well as freshwater
Symmetry	Usually dorsoventrally flattened	Usually bilateral symmetry
Endo-skeleton	Cartilaginous	Mostly bony
Caudal fin	Heterocrecal	Heterocercal or diphyceral
Pelvic fin	Usually posterior	Mostly anterior, occasionally posterior
Mouth	Large, crescent shaped on the ventral side of the head	Variable shape and size at the tip or terminal part of the head
Gill slit	Usually five pairs of gill slits which are not protected by an operculum	Five pairs of gill slits protected by an operculum
Cloaca	A true cloaca is present	In most bony fishes, the cloaca is absent, and the anus, urinary and genital apertures open separately
Stomach	Typically J-shaped	Shape variable. Absent in some
Intestine	Short with spiral valve in lumen	Long with no spiral valve
Liver	Usually has two lobes	Usually has three lobes
Brain	Has large olfactory lobe, cerebrum and small optic lobe and cerebellum	Has small olfactory lobes and cerebrum and large optic lobes and cerebellum
Retina	Lacks cone cell	a pair of cone cells preesnt
Eggs	A small number of large eggs with plenty of yolk	A large number of small eggs with little yolk
Fertilisation	Internal	Usually external
Development	internally	externally
Examples	Scolidon, Electric ray, string ray, Sharks	Labeo, catla, Hilsa, Wallago, Hippocampus