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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 .
According to the fossil record, the divergence of coelacanths, lungfish, and tetrapods is thought to have occurred during the Silurian. [47] Over 100 fossil species of coelacanth have been described. [46] The oldest identified coelacanth fossils are around 420–410 million years old, dating to the early Devonian.
There is a layer of enamel and even a layer of pulp. The whole shield is made up of thousands of small teeth fused together. This bony skull--one of the earliest in the fossil record--is made entirely of little teeth. Teeth originally arose to bite creatures (see Conodonts); later a version of teeth was used in a new way to protect them." [4]
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 vertebrate apex predators of any ecosystem.
The class Osteostraci (meaning "bony shells") is an extinct taxon of bony-armored jawless fish, termed "ostracoderms", that lived in what is now North America, Europe and Russia from the Middle Silurian to Late Devonian. Anatomically speaking, the osteostracans, especially the Devonian species, were among the most advanced of all known ...
The order Arthrodira belongs to the class Placodermi, the large group of extinct prehistoric armored fish that is thought to have diverged over 400 million years ago from all sharks and bony fishes (and thus also all subsequent tetrapods, including mammals, birds, reptiles and amphibians).
One of the coolest, most prehistoric-looking fish lives in Florida’s offshore waters of the Gulf of Mexico. It happens to be one of the best to eat but also one of the most elusive.
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