Difference between Cartilaginous Fish and Bony Fish
November 11, 2024 
written by Almas Anwar
written by Almas AnwarThe main difference between cartilaginous fish and bony fish is in their skeleton. Cartilaginous fish are marine animals and have endoskeleton made entirely of cartilage. While bony fish are found in fresh water as well as marine water, and their endoskeleton is made of bones.
Likewise, the exoskeleton of cartilaginous fish is made of ‘placoid’ scales, known as denticles. While exoskeleton of bony fish may contain different types of scales — cycloid, ctenoid, or ganoid.
Fishes are classified into two groups: Chondrichthyes and Osteichthyes (cartilaginous and bony fish). Based on this classification, both the groups have different anatomy and characteristics.
Cartilaginous fish Vs. Bony fish
Here are the key differences between cartilaginous fish and bony fish:
| Characters | Cartilaginous Fish | Bony Fish |
| Classification | Phylum- Chordates Class- Chondrichthyes | Phylum- Chordata Class- Osteichthyes |
| Habitat | Found in marine water | Found in both; marine and freshwater |
| Skeleton | Made up of cartilage | Made up of bones |
| Scales | Placoid (teeth-like) scales that are embedded with the skin, called denticles. | Can have different types of scales: cycloid (smooth and round), ctenoid (rough and comb-edged), and ganoid (thick). |
| Gills | 5-7 pairs of gills | 4 pairs of gills |
| Alternative name | Elasmobranchii | Teleostomi |
| Mouth position | Mouth located on the underside | Have moth at the front tip |
| Jaw set | Have a single set of oral jaws with sharp teeth | Have two sets of oral jaws |
| Air Bladder | Have an oil-filled liver for buoyancy. | Have a swim bladder for buoyancy. |
| Fertilization | Exhibits internal fertilization and give birth to live young (viviparous), or lay eggs (oviparous) | External fertilization |
| Excretion | Excretes urea | Excretes ammonia |
| Number of species | More than 970 species have been identified | Almost 27,000 species that are identified worldwide |
| Examples | Examples include: Sharks, Rays, Skates. | Examples include: Salmon, Rohu, Trout, Seahorse, Flying fish. |
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