Teleost

Teleosts are the dominant fish of the present day. They arose in the Mesozoic era, and include 20,000 living species. The oldest teleost fossils date back to the late Triassic. They evolved from fish like bowfins in the clade Holostei. During the Mesozoic and Cainozoic they diversified. 96 percent of all known fish species are teleosts.
They are, in order of evolution, vertebrates, jawed fish (Gnathostomata), bony fish (Osteichthyes) and ray-finned fish (Actinopterygii).
Advantages.
To account for their success, teleosts must have advantages over earlier fish. In general, teleosts tend to be quicker and more flexible than earlier bony fishes. Their skeletal structure has evolved towards greater lightness. Teleost bones are constructed from a scaffolding of struts, which makes them strong without adding weight.
Teleosts have a movable jaw and changes in the jaw muscles. These changes make it possible for them to protrude their jaws outwards from the mouth. This adaptation improves their ability to grab fast-moving prey.
Date of origin.
The date of origin of the teleosts is a difficult problem. Two kinds of evidence are available. There is evidence from the fossil record that the first teleost comes from the late Triassic period.
This date is somewhat later than molecular divergence time estimates (molecular clock). A recent paper finds that fossil dates and molecular clock dates are similar to each other. These researchers state:
Teleost superorders.
Teleostei