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A fossil specimen of Onychodus from Western Australia was found with a placoderm fish half its length logged in its throat. [20] [21] This interesting find was described and illustrated by Dr. John A. Long. [4] [19] [21] The pectoral fins were strong enough for the animal to "walk" around the sea floor in search of a hiding place between coral ...
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 .
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 individual teeth are widely separated from each other in the tooth whorls. [16] The teeth themselves are of the cladodont variety; the bases of the teeth are broadest on the lingual side, and each support a single large cusp and two pairs of smaller accessory cusps for a total of five cusps. [16]
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.
Helicoprion is a genus of extinct 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.
Stratodus is a genus of giant prehistoric aulopiform fish found in Cretaceous-aged marine strata of Kansas, [1] Alabama, [2] Morocco, [3] Israel, [4] and Niger, [5] South Dakota, [6] Jordan. [7] It has also been found in the Tamaguélelt Formation of Mali , dating to the Lower Eocene , indicating that Stratodus survived the Cretaceous-Paleogene ...