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Dunkleosteus is an extinct genus of large arthrodire ("jointed-neck") fish that existed during the Late Devonian period, about 382–358 million years ago.It was a pelagic fish inhabiting open waters, and one of the first apex predators of any ecosystem.
Placoderms were among the first jawed fish (their jaws likely evolved from the first pair of gill arches), as well as the first vertebrates to have true teeth. They were also the first fish clade to develop pelvic fins , the second set of paired fins and the homologous precursor to hindlimbs in tetrapods .
The study of prehistoric fish is called paleoichthyology. A few living forms, such as the coelacanth are also referred to as prehistoric fish, or even living fossils, due to their current rarity and similarity to extinct forms. Fish which have become recently extinct are not usually referred to as prehistoric fish. They were very different from ...
Within cartilaginous fish, approximately 80% of the sharks, rays, and skates families survived the extinction event, [114] and more than 90% of teleost fish (bony fish) families survived. [115] There is evidence of a mass kill of bony fishes at a fossil site immediately above the K–T boundary layer on Seymour Island near Antarctica ...
Helicoprion is an extinct genus of shark-like [1] eugeneodont fish. Almost all fossil specimens are of spirally arranged clusters of the individuals' teeth, called "tooth whorls", which in life were embedded in the lower jaw. As with most extinct cartilaginous fish, the skeleton is mostly unknown.
The braincase of lobe-finned fish primitively has a hinge line, but this is lost in tetrapods and lungfish. Many early lobe-finned fish have a symmetrical tail. All lobe-finned fish possess teeth covered with true enamel. Lobe-finned fish, such as coelacanths and lungfish, were the most diverse
Among the fish that have been caught were about equal numbers of males and females. [8] Population estimates range from 210 individuals per population to 500 per population. [ 8 ] [ 65 ] Because coelacanths have individual color markings, scientists think that they recognize other coelacanths via electric communication .
Xiphactinus (from Latin and Greek for "sword-ray") is an extinct genus of large predatory marine ray-finned fish that lived during the late Albian to the late Maastrichtian. [4] The genus grew up to 5–6 metres (16–20 ft) in length, and superficially resembled a gargantuan, fanged tarpon .