Cartilaginous fish

Cartilaginous fish are a group of fish that have skeletons made of cartilage rather than bone. This group includes sharks, rays, and chimaeras. They are classified under the class Chondrichthyes, which is divided into two subclasses: Elasmobranchii (sharks and rays) and Holocephali (chimaeras).

Characteristics

Cartilaginous fish are characterized by their cartilage skeletons. Unlike bony fish, their skeletons are not calcified, which makes them lighter and more flexible. They also have tooth-like scales called dermal denticles that protect their skin from damage and parasites, and also reduce friction while swimming.

Another unique feature of cartilaginous fish is their jaws. The upper jaw is not fused to the skull, allowing it to move separately. This is a significant evolutionary adaptation that has allowed these fish to become successful predators.

Evolution

The first cartilaginous fish appeared in the Silurian period, around 450 million years ago. They are among the oldest groups of fish in the fossil record. The evolution of cartilaginous fish is closely tied to the evolution of their jaws, which have allowed them to become successful predators.

Diversity

There are over 1,000 species of cartilaginous fish. They range in size from small species like the pygmy shark, which is only about 25 cm long, to the whale shark, the largest fish in the world, which can reach lengths of over 12 meters.

Conservation

Many species of cartilaginous fish are threatened by overfishing, habitat loss, and pollution. Some species, like the great white shark and the manta ray, are listed as vulnerable or endangered on the IUCN Red List.

See also

• Bony fish
• Fish anatomy
• Fish scale
• Shark
• Ray (fish)
• Chimaera