Cretoxyrhina

Cretoxyrhina is an extinct genus of large mackerel shark that lived about 107 to 73 million years ago during the late Albian to late Campanian of the Late Cretaceous period. The type species, C. mantelli, is more commonly referred to as the Ginsu shark. Measuring up to 8 meters in length and weighing over 4,944 kilograms, it was one of the largest sharks of its time.

About Cretoxyrhina in brief

Cretoxyrhina is an extinct genus of large mackerel shark that lived about 107 to 73 million years ago during the late Albian to late Campanian of the Late Cretaceous period. The type species, C. mantelli, is more commonly referred to as the Ginsu shark. Measuring up to 8 meters in length and weighing over 4,944 kilograms, it was one of the largest sharks of its time. It was an apex predator in its ecosystem and preyed on a large variety of marine animals including mosasaurs and plesiosaurs, sharks and other large fish, pterosaurs, and occasionally dinosaurs. It has been speculated that the shark hunted by lunging at its prey at high speeds to inflict powerful blows, similar to the great white shark today, and relied on strong eyesight to do so. It preferred mainly subtropical to temperate pelagic environments but was known in waters as cold as 5 °C. It saw its peak in size by the Coniacian, but subsequently experienced a continuous decline until its extinction during the Campanian. Its lifespan has been calculated to extend to nearly forty years. Its fossils have been found worldwide, although most frequently in the Western Interior Seaway area of North America. The shark possessed facial and optical features most similar to that in thresher sharks and crocodile sharks and had a hydrodynamic build that suggested the use of regional endothermy. It also had thick enamel built for stabbing and slicing prey. It is thought to have been among the fastest-swimming sharks, with hydrod dynamic calculations suggesting burst speed capabilities of up to 70 kilometers per hour.

It may have been killed by competition with predators that arose around the same time, most notably the giant mosasaur Tylosaurus, Other possible factors include the gradual disappearance of the Western interior Seaway. It had a similar appearance and build to the modernGreat white shark, and was a cosmopolitan genus and its fossils have were found worldwide. Since the late 19th century, several fossils of exceptionally well-preserved skeletons have been discovered in Kansas. Most of these were derived from teeth that represented variations of these species of shark. According to some paleontologists, there may have as much as almost 30 different synonyms of O. mantelli at the time of the discovery of these fossils. The species was first described by the English paleontologist Gideon Mantell from eight C.  mantelli teeth he collected from the Southerham Grey Pit near Lewes, East Sussex. In his 1822 book The fossils of the South Downs, he identified them as teeth pertaining to two species of locally-known modern sharks. In 1843, Swiss naturalist Louis Agassiz published the third volume of his book Recherches sur les poissons fossiles, where he reexamined Mantell’s eight teeth. Using them and another tooth from the collection of the Strasbourg Museum, he concluded that the fossils actually pertained to a single species of extinct shark that held strong dental similarities with the common smooth-hound.

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