What is extant fish?

Extant fish are those fish species that still exist in the present day and are not extinct. They have a diverse range of characteristics and adaptations that enable them to survive in various aquatic environments, including freshwater, saltwater, deep oceans, and shallow streams.

There are over 34,000 known species of extant fish, making them the most diverse group of vertebrates on the planet. They vary in size, shape, color, and behavior, and are categorized into several different groups or classes, including jawless fish, cartilaginous fish, and bony fish.

Jawless fish include lampreys and hagfish and are characterized by their lack of a true jaw. Cartilaginous fish, such as sharks, rays, and skates, have a skeleton made of cartilage instead of bone. Bony fish make up the largest group of extant fish and include over 95% of all fish species. They have a bony skeleton, a swim bladder, and gills that extract oxygen from the water.

Extant fish play an important role in aquatic ecosystems, serving as a food source for many other aquatic animals, including humans. They are also essential for maintaining the balance of marine and freshwater ecosystems and are often used as indicators of water quality.

Overall, extant fish are a fascinating and diverse group of animals that continue to play a crucial role in the natural world.