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As one species evolves into another, its teeth may become difficult to classify, exhibiting characteristics of both species. (Example: teeth from Otodus auriculatus as it evolved into O. angustidens) are difficult to definitively identify as coming from either species. Otodus megalodon fossil shark jaw (reconstruction) (late Cenozoic) 2
Shark teeth are strong and made of enamel. Many sharks have 3 rows of teeth. These teeth are embedded in the gums, not the jaw. [10] Sharks are born with teeth that are constantly being replaced. Teeth are replaced every two weeks, approximately. [10] The shape of the teeth determine the diet of the shark.
In most oviparous shark species, an egg case with the consistency of leather protects the developing embryo(s). These cases may be corkscrewed into crevices for protection. The egg case is commonly called a mermaid's purse. Oviparous sharks include the horn shark, catshark, Port Jackson shark, and swellshark. [80] [82]
This species was later moved to the genus Carcharhinus. [2] The specific epithet isodon means "equal teeth" in Greek, and refers to the similar number of teeth in the upper and lower jaws. [3] This species may also be referred to as the eventooth shark, smoothtooth shark, or night shark (usually used for C. signatus). [4]
The top jaw has jagged, cusped teeth and the bottom jaw has comb-shaped teeth. Its single dorsal fin is set far back along the spine towards the caudal fin, and is behind the pelvic fins. In this shark the upper caudal fin is much longer than the lower, and is slightly notched near the tip. Like many sharks, this sevengill is counter-shaded.
The fact that the bite marks were found on the tooth's roots further suggest that the shark broke the whale's jaw during the bite, suggesting the bite was extremely powerful. The fossil is also notable as it stands as the first known instance of an antagonistic interaction between a sperm whale and an otodontid shark recorded in the fossil record.
It contains one extant species, the snaggletooth shark (H. elongata) and several extinct species. Hemipristis has two distinct types of teeth in each section of its jaw. The ones on the upper jaw act as knives, cutting through the flesh of the prey, while the pointed ones on the bottom act as forks, spearing the prey and holding it down.
Ptychodus was a large shark, previously estimated at 10 meters (33 feet) long based on extrapolation from teeth. [ 13 ] [ 14 ] The subadult specimen with the largest vertebra showed that it could reach lengths of 4.3–7.07 m (14.1–23.2 ft), so a 10 m (33 ft) length is possible, but more analysis is required for verification.