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It is the largest class of vertebrates in existence today, encompassing most aquatic vertebrates, as well as all semi-aquatic and terrestrial vertebrates. The group is divided into two main clades , the ray-finned fish ( Actinopterygii , which makes up the vast majority of extant fish) and the lobe-finned fish ( Sarcopterygii , which gave rise ...
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.
Osteichthyes (bone-fish) or bony fishes are a taxonomic group of fish that have bone, as opposed to cartilaginous skeletons. The vast majority of fish are osteichthyans, which is an extremely diverse and abundant group consisting of 45 orders, with over 435 families and 28,000 species. [21] It is the largest class of vertebrates in existence today.
The vertebrates make up the subphylum Vertebrata with some 65,000 species, by far the largest grouping in the phylum Chordata. The vertebrates include mammals, birds, amphibians, and various classes of fish and reptiles. The fish include the jawless Agnatha, and the jawed Gnathostomata. The jawed fish include both the cartilaginous fish and the ...
Fish typically have quite small brains relative to body size compared with other vertebrates, typically one-fifteenth the brain mass of a similarly sized bird or mammal. [59] However, some fish have relatively large brains, most notably mormyrids and sharks, which have brains about as massive relative to body weight as birds and marsupials .
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.
The deep sea bathypelagic bony-eared assfish [138] has the smallest ratio of all known vertebrates. [139] Elephantnose fish: At the other extreme, the elephantnose fish, an African freshwater fish, has an exceptionally large brain-to-body weight ratio. These fish have the largest brain-to-body oxygen consumption ratio of all known vertebrates ...
A 319-million-year-old fossilised fish has revealed the oldest example of a well-preserved vertebrate brain, according to scientists. University of Birmingham and University of Michigan (USA ...