page_title: Cretoxyrhina
section_title: Dentition
hierarchical_section_title: Cretoxyrhina / Biology / Morphology / Dentition
caption_attribution_description: English: Life reconstruction of the ginsu shark (Cretoxyrhina mantellii) based on Shimada (1997) and Sternes &amp; Shimada (2018).
context_page_description: 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, 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 meters in length and weighing over 4,944 kilograms The calculated weight of a 7-meter individual, 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 and plesiosaurs, sharks and other large fish, pterosaurs, and occasionally dinosaurs. Its teeth, up to 8 centimeters in height, were razor-like and had thick enamel built for stabbing and slicing prey.
context_section_description: Distinguishing characteristics of Cretoxyrhina teeth include a nearly symmetrical or slanted triangular shape, razor-like and non-serrated cutting edges, visible tooth necks (bourlette), and a thick enamel coating. The dentition of Cretoxyrhina possesses the basic dental characteristics of a mackerel shark, with tooth rows closely spaced without any overlap. Anterior teeth are straight and near-symmetrical, while lateroposterior teeth are slanted. The side of the tooth facing the mouth is convex and possesses massive protuberance and nutrient grooves on the root, whereas the labial side, which faces outwards, is flat or slightly swollen. Juveniles possessed lateral cusplets in all teeth, and C. vraconensis consistently retained them in adulthood. Lateral cusplets were retained only up to all lateroposterior teeth in adulthood in C. denticulata and C. agassizensis and only up to the back lateroposterior teeth in C. mantelli. The lateral cusplets of C. vraconensis and C. denticulata are round, while in C. agassizensis are sharpened to a point. The anterior teeth of C. vraconensis measure 2.1–3.5 centimeters (0.8–1.4 in) in height, while the largest known tooth of C. denticulata measures 3 centimeters (1.2 in). C. mantelli teeth are larger, measuring 3–4 centimeters (1–2 in) in average slant height. The largest tooth discovered from this species may have measured up to 8 centimeters (3 in).
  The dentition of C. mantelli is among the best-known of all extinct sharks, thanks to fossil skeletons like FHSM VP-2187, which consists of a near-complete articulated dentition. Other C. mantelli skeletons, such as KUVP-247 and KUVP-69102, also include partial jaws with some teeth in their natural positions, some of which were not present in more complete skeletons like FHSM VP-2187. Using these specimens, the dental formula was reconstructed by Shimada (1997) and revised by Shimada (2002), it was . This means that from front to back, C. mantelli had: four symphysials (small teeth located in the symphysis of a jaw), two anteriors, four intermediates, and eleven or more lateroposteriors for the upper jaw and possibly one symphysial, two anteriors, one intermediate, and fifteen or more lateroposteriors for the lower jaw. The structure of the tooth row shows a dental structure suited for a feeding behavior similar to modern mako sharks, having large spear-like anteriors to stab and anchor prey and curved lateroposteriors to cut it to bite-size pieces, a mechanism often informally described as "slicing and dicing" by paleontologists. In 2011, paleontologists Jim Bourdon and Mike Everhart reconstructed the dentition of multiple C. mantelli individuals based on their associated tooth sets. They discovered that two of these reconstructions show some notable differences in the size of the first intermediate (I1) tooth and lateral profiles, concluding that these differences could possibly represent sexual dimorphism or individual variations.
caption: Reconstruction of C. mantelli
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