Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Pages: 105. Not illustrated. Chapters: Onychodus, Tiktaalik, Xiphactinus, Cladoselache, Helicoprion, Cheirolepis, Xenacanthus, Harpagofututor, Stethacanthus, Coelacanthus, Diplomystus, Coccosteus, Acanthodes, Ischyodus, Knightia, Listracanthus, Scapanorhynchus, Climatius, Glikmanius, Bananogmius, Oncorhynchus Rastrosus, Orodus, Cobelodus, Cimolichthys, Saurodon, Caridosuctor, Iniopteryx, Allenypterus, Aleosteus, Caproberyx, Rhabdoderma, Ctenaspis, Sarcoprion. Excerpt: Onychodus (pronounced , from Greek meaning "claw-tooth") is a genus of prehistoric lobe-finned fish which lived during the Devonian period (Eifelian - Famennian stages, around 374 to 397 million years ago). It is one of the best known of the group of onychodontiform fishes. Scattered fossil bones of Onychodus were first discovered in 1857, in North America, and described by John Strong Newberry. Other species were found in Australia, England, Norway and Germany showing that it had a widespread range. Onychodus was about 2 to 3 meters in length and was a pelagic animal. Like other onychodontiformes, it had a pair of tooth spirals (parasymphysial tooth whorls) bearing tusk-like teeth. The most well-preserved specimen of Onychodus has been found at the Gogo Formation of Western Australia giving palaeontologists more information about the structure of the fish. Other species of Onychodus are known only from poor material based on isolated tusks, teeth and scales. A skull diagram of Onychodus.The most characteristic feature is a pair of retractable, laterally compressed tusk whorls at the front of the lower jaw. These were not attached to any other bone, but fit into a pair of deep cavities on the palate and were free to move. The lower jaw was connected with the upper jaw in a way that made the tusk whorl thrust out as a dagger when the head was raised. The upper jaw, containi...
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