A fish is an aquatic, anamniotic, gill -bearing vertebrate animal with swimming fins and a hard skull, but lacking limbs with digits. Fish can be grouped into the more basal jawless fish and the more common jawed fish, the latter including all living cartilaginous and bony fish, as well as the extinct placoderms and acanthodians. In a break from the long tradition of grouping all fish into a ...
A fish is any of approximately 34,000 species of vertebrate animals found in the world’s fresh and salt waters. The term fish is applied to a variety of vertebrates of several evolutionary lines. It describes a life-form rather than a taxonomic group.
All fish share two traits: they live in water and they have a backbone—they are vertebrates. Apart from these similarities, however, many of the species in this group differ markedly from one...
Instead, there are 3 main classes, groups, or types of fish: bony fish (Osteichthyes), jawless fish (Agnatha), and cartilaginous fish (Chondrichthyes). Fish are the most diverse group among vertebrates, with over 33,000 different types of fish species.