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All vertebrate jaws, including the human jaw, evolved from early fish jaws. The appearance of the early vertebrate jaw has been described as "perhaps the most profound and radical evolutionary step in the vertebrate history". [4] [5] Fish without jaws had more difficulty surviving than fish with jaws, and most jawless fish became extinct.
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.
Within the chondrichthyans, horn sharks (Heterodontidae), some rays (Myliobatidae) and chimeras (Holocephali) exhibit durophagous behaviour. They have adaptations to allow for this including stout flattened teeth, hypertrophied jaw adductor muscles and robust jaws to feed on hard prey such as crustaceans and molluscs.
For human beings and 99.8% of our fellow vertebrates, having jaws is an integral part of life. Researchers on Wednesday described the earliest-known vertebrates that possessed jaws as revealed by ...
The teeth sit outside of the mouth, interlocking, with two large lower fangs that curl upward reaching past the fish’s eyes. Because its jaw can unhinge, the viperfish can eat large prey for its ...
Osteichthyes (bone-fish) or bony fishes are a taxonomic group of fish that have bone, as opposed to cartilaginous skeletons. The vast majority of fish are osteichthyans, which is an extremely diverse and abundant group consisting of 45 orders, with over 435 families and 28,000 species. [21] It is the largest class of vertebrates in existence today.
The shark hits the crocodile with the bump-and-bite technique. Accustomed to defending himself against rivals, the crocodile bites the shark's tail, but cannot get a good grip. The shark swims off and makes a wide turn for a full-on assault; all of a sudden, the crocodile gets the first bite on her right pectoral fin.
The video above shows the fascinating way male giraffes fight. Known as “necking” the giraffes use their long and powerful necks to attack, delivering hard blows with each hit.