Cretoxyrhina

Cretoxyrhina Temporal range: Albian-Campanian, 107.59–73.2 Ma[1][2][3][4][5][6] PreꞒ Ꞓ O S D C P T J K Pg N
Cretoxyrhina mantelli tooth from New Jersey, USA; Naturhistorisches Museum (Vienna)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii
Subdivision:	Selachimorpha
Order:	Lamniformes
Family:	†Cretoxyrhinidae Glückman, 1958
Genus:	†Cretoxyrhina Glückman, 1958
Type species
†Cretoxyrhina mantelli Agassiz, 1835
Other species
†C. denticulata Glückman, 1957 †C. vraconensis Zhelezko, 2000 †C. agassizensis Underwood & Cumbaa, 2010
Synonyms[7][8][9][10][11]
List of synonyms Genus Squalus Squalus mustelus Mantell, 1822 Squalus zygaena Mantell, 1822 Squalus acaule Nilsson, 1827 Genus Lamna Lamna mantellii Agassiz, 1835 Lamna acuminata Agassiz, 1838 Lamna cornubica Schimdt, 1846 Lamna petricoriensis Coquand, 1860 Lamna (Sphenodus) longidens Agassiz, 1876 Genus Oxyrhina Oxyrhina mantellii Agassiz, 1838 Oxyrhina subinflata Agassiz, 1876 Oxyrhina extenta Leidy, 1873 Genus Otodus Otodus appendiculatus Agassiz, 1838 Otodus oxyrhinoides Sauvage, 1872 Genus Isurus Isurus mantelli Agassiz, 1843 Isurus denticulatus Glückman, 1957 Genus Pseudoisurus Pseudoisurus mantelli Zhelezko, 2000 Pseudoisurus vraconensis Zhelezko, 2000 Genus Telodontaspis Telodontaspis agassizensis Underwood & Cumbaa, 2010

Cretoxyrhina (/krɪˌtɒksiˈrhaɪnə/; meaning 'Cretaceous sharp-nose') 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. The type species, C. mantelli, is more commonly referred to as the Ginsu shark, first popularized in reference to the Ginsu knife, as its theoretical feeding mechanism is often compared with the "slicing and dicing" when one uses the knife. Cretoxyrhina is traditionally classified as the likely sole member of the family Cretoxyrhinidae but other taxonomic placements have been proposed, such as within the Alopiidae and Lamnidae.

Measuring up to 8 m (26 ft) in length and weighing over 4,944 kg (10,900 lb), Cretoxyrhina was one of the largest sharks of its time. Having a similar appearance and build to the modern great white shark, it was an apex predator in its ecosystem and preyed on a large variety of marine animals including mosasaurs, plesiosaurs, sharks and other large fish, pterosaurs, and occasionally dinosaurs. Its teeth, up to 8 cm (3.1 in) long, were razor-like and had thick enamel built for stabbing and slicing prey. Cretoxyrhina was also among the fastest-swimming sharks, with hydrodynamic calculations suggesting burst speeds of up to 70 km/h (43 mph).^[a] It has been speculated that Cretoxyrhina 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.

Since the late 19th century, several fossils of exceptionally well-preserved skeletons of Cretoxyrhina have been discovered in Kansas. Studies have successfully calculated its life history using vertebrae from some of the skeletons. Cretoxyrhina grew rapidly during early ages and reached sexual maturity at around four to five years of age. Its lifespan has been calculated to extend to nearly forty years. Anatomical analysis of the Cretoxyrhina skeletons revealed that 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.

As an apex predator, Cretoxyrhina played a critical role in the marine ecosystems it inhabited. It was a cosmopolitan genus and its fossils have been found worldwide, although most frequently in the Western Interior Seaway area of North America. It preferred mainly subtropical to temperate pelagic environments but was known in waters as cold as 5 °C (41 °F). Cretoxyrhina saw its peak in size by the Coniacian, but subsequently experienced a continuous decline until its extinction during the Campanian. One factor in this demise may have been increasing pressure from 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.

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