Differences between Chondrichthyes and Osteichthyes

 

Feature	Chondrichthyes	Osteichthyes
Common Name	Cartilaginous fishes	Bony fishes
Habitat	Exclusively marine animals	Marine and freshwater fishes
Endoskeleton	Cartilaginous	Bony
Body Shape	Streamlined body	Streamlined body
Mouth Position	Ventrally located	Mostly terminal
Gills	Gill slits are separate and naked	Four pairs of gills covered by operculum
Scales	Skin is tough, containing minute placoid scales	Skin is covered with cycloid/ctenoid scales
Teeth	Modified placoid scales, backwardly directed	Derived from bones
Jaws	Very powerful	Well-developed jaws
Mode of feeding	Predaceous	Vary from filter feeders to predators
Notochord	Persistent throughout life	Replaced by bony vertebral column in adult
Air Bladder	Absent, requiring constant swimming to avoid sinking	Present, regulates buoyancy
Heart	Two-chambered (venous heart), single circulation.	Two-chambered (venous heart), single circulation.
Body Temperature	Cold-blooded (poikilothermous) animals	Cold-blooded (poikilothermous) animals
Sexes	Separate	Separate
Fertilization	Internal	Usually, external
Development	Many of them are viviparous	Mostly oviparous and development is direct
Special Features	Some have electric organs (e.g., Torpedo); some possess poison sting (e.g., Trygon). In males, pelvic fins bear claspers.	Males bear brood pouch in Hippocampus
Examples	Scoliodon (Dog fish), Pristis (Saw fish), Carcharodon (Great white shark), Trygon (Sting ray)	Marine: Exocoetus (Flying fish), Hippocampus (Sea horse); Freshwater: Labeo (Rohu), Catla (Katla), Clarias (Magur); Aquarium: Betta (Fighting fish), Pterophyllum (Angel fish)