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A fish (pl.: fish or fishes) 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.
The olfactory lobes are very large in fish that hunt primarily by smell, such as hagfish, sharks, and catfish. Behind the olfactory lobes is the two-lobed telencephalon, the structural equivalent to the cerebrum in higher vertebrates. In fish the telencephalon is concerned mostly with olfaction. [59] Together these structures form the forebrain.
Lionfish have 18 venomous spines total: 2 pelvic spines, 3 anal spines, and 13 dorsal spines. Pterois is a genus of venomous marine fish, commonly known as the lionfish, native to the Indo-Pacific.
The fish include the jawless Agnatha, and the jawed Gnathostomata. The jawed fish include both the cartilaginous fish and the bony fish. Bony fish include the lobe-finned fish, which gave rise to the tetrapods, the animals with four limbs. Despite their success, vertebrates still only make up less than five percent of all described animal species.
Bony fish can be further divided into those with lobe fins and those with ray fins. Lobe fins have the form of fleshy lobes supported by bony stalks which extend from the body. [16] Lobe fins evolved into the legs of the first tetrapod land vertebrates, so by extension an early ancestor of humans was a lobe-finned fish.
Total fish production in 2016 reached an all-time high of 171 million tonnes, of which 88% was utilized for direct human consumption, resulting in a record-high per capita consumption of 20.3 kg (45 lb). [12] Since 1961 the annual global growth in fish consumption has been twice as high as population growth.
A newfound fossil of a jawless fish is the oldest known vertebrate cranium preserved in 3D. The 455 million-year-old find could illuminate how vertebrate heads evolved.
Pteraspidomorphi is an extinct class of early jawless fish ancestral to jawed vertebrates. The few characteristics they share with the latter are now considered as primitive for all vertebrates. Around the start of the Devonian, fish started appearing with a deep remodelling of the vertebrate skull that resulted in a jaw. [323]