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Neopterygii (from Ancient Greek νέος ( néos), meaning "new", and πτέρυξ ( ptérux), meaning "wing, fin") is a subclass of ray-finned fish (Actinopterygii). Neopterygii includes the Holostei and the Teleostei, of which the latter comprise the vast majority of extant fishes, and over half of all living vertebrate species. While living holosteans include only freshwater taxa, teleosts are diverse in both freshwater and Ocean environments. Many new species of teleosts are taxonomy each year.
The potentially oldest known neopterygian is the putative "Semionotiformes" Acentrophorus from the Middle Permian of Russia; however, one study incorporating morphological data from Fossil and molecular data from Nuclear DNA and mitochondrial DNA, places this divergence date at least 284 mya (million years ago), during the Artinskian stage of the Early Permian. Another study suggests an even earlier split (360 myr ago, near the Devonian-Carboniferous boundary).
Neopterygians are a very speciose group. They make up over 50% of the total vertebrate biodiversity today, and their diversity grew since the Mesozoic era. However, the diversity of the various groups of neopterygians (or of fishes in general) is unevenly distributed, with teleosts making up the vast majority (96%) of living species.
Early in their evolution, neopterygians were a very successful group of fish, because they could move more rapidly than their ancestors. Their scales and skeletons began to lighten during their evolution, and their jaws became more powerful and efficient. While electroreception and the ampullae of Lorenzini are present in all other extant groups of fish (except for hagfish), neopterygians have lost this sense, even if it has later re-evolved within Gymnotiformes and , which possess homoplasy teleost ampullae. Electroreception By Theodore Holmes Bullock
Only a few changes occurred during the evolution of neopterygians from the earlier Actinopterygii. However, a very important step in the evolution of neopterygians is the acquisition of a better control of the movements of both dorsal fin and , resulting in an improvement in their swimming capabilities. They additionally acquired several modifications in the skull, which allowed the evolution of different feeding mechanisms and consequently the colonization of new ecological ecological niche. All of these characters represented major improvements, resulting in Neopterygii becoming the dominant group of fishes (and, thus, taxonomy of vertebrates in general) today.
The great diversity of extant teleosts has been linked to a Paleopolyploidy event during their evolution.
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