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Chondrichthyes (/ k ɒ n ˈ d r ɪ k θ i iː z /; from Ancient Greek χόνδρος (khóndros) 'cartilage' and ἰχθύς (ikhthús) 'fish') is a class of jawed fish that contains the cartilaginous fish or chondrichthyans, which all have skeletons primarily composed of cartilage.
Ostariophysi is the second-largest superorder of fish.Members of this superorder are called ostariophysians.This diverse group contains 10,758 species, about 28% of known fish species in the world and 68% of freshwater species, and are present on all continents except Antarctica.
Fish account for more than half of vertebrate species. As of 2016, there are over 32,000 described species of bony fish, over 1,100 species of cartilaginous fish, and over 100 hagfish and lampreys. A third of these fall within the nine largest families; from largest to smallest, these are Cyprinidae , Gobiidae , Cichlidae , Characidae ...
Osteichthyes (/ ˌ ɒ s t iː ˈ ɪ k θ iː z / ost-ee-IK-theez; from Ancient Greek ὀστέον (ostéon) 'bone' and ἰχθύς (ikhthús) 'fish'), [2] also known as osteichthyans or commonly referred to as the bony fish, is a diverse superclass of vertebrate animals that have endoskeletons primarily composed of bone tissue.
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.
A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found in most fish, in mammals such as whales, and in extinct ancient marine reptiles such as ichthyosaurs ...
After the appearance of jawed fish (placoderms, acanthodians, sharks, etc.) about 420 million years ago, most ostracoderm species underwent a decline, and the last ostracoderms became extinct at the end of the Devonian period. More recent research indicates that fish with jaws had far less to do with the extinction of the ostracoderms than ...
Rhenanida ("Rhine fish") were flattened, ray-like, bottom-dwelling predators with large, upturned mouths that lived in marine environments. The rhenanids were once presumed to be the most primitive, or at least the closest to the ancestral placoderm, as their armour was made of unfused components—a mosaic of tubercles—as opposed to the ...