| Cretoxyrhina | |
|---|---|
| |
| Cretoxyrhina mantelli tooth from New Jersey, USA; Naturhistorisches Museum (Vienna) | |
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Elasmobranchii |
| Order: | Lamniformes |
| Family: | †Cretoxyrhinidae Glückman, 1958 |
| Genus: | †Cretoxyrhina Glückman, 1958 |
| Type species | |
| †Cretoxyrhina mantelli (Agassiz, 1835)
| |
| Other species | |
| |
| Synonyms[7][8][9][10][11] | |
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.
- ^ Kenshu Shimada (1997). "Stratigraphic Record of the Late Cretaceous Lamniform Shark, Cretoxyrhina mantelli (Agassiz), in Kansas". Transactions of the Kansas Academy of Science. 100 (3/4): 139–149. doi:10.2307/3628002. JSTOR 3628002.
- ^ Mikael Siverson; Johan Lindgren (2005). "Late Cretaceous sharks Cretoxyrhina and Cardabiodon from Montana, USA" (PDF). Acta Palaeontologica Polonica. Archived (PDF) from the original on 2017-08-09. Retrieved 2018-11-24.
- ^ David Ward (2009). Fossils of the Gault Clay – Sharks and Rays. The Palaeontological Association. pp. 279–299.
- ^ James G. Ogg; Linda A. Hinnov (2012), "Cretaceous", in Felix M. Gradstein; James G. Ogg; Mark D. Schmitz; Gabi M. Ogg (eds.), The Geologic Time Scale, Oxford: Elsevier, pp. 793–853, doi:10.1016/B978-0-444-59425-9.00027-5, ISBN 978-0-444-59425-9, S2CID 127523816
- ^ Todd Cook; Eric Brown; Patricia E. Ralrick; Takuya Konishi (2017). "A late Campanian euselachian assemblage from the Bearpaw Formation of Alberta, Canada: some notable range extensions". Canadian Journal of Earth Sciences. 54 (9): 973–980. Bibcode:2017CaJES..54..973C. doi:10.1139/cjes-2016-0233. hdl:1807/77762.
- ^ Derek William Larson; Donald B. Brinkman; Phil R. Bell (2010). "Faunal assemblages from the upper Horseshoe Canyon Formation, an early Maastrichtian cool-climate assemblage from Alberta, with special reference to the Albertosaurus sarcophagus bonebed". Canadian Journal of Earth Sciences. 47 (9): 1159–1181. Bibcode:2010CaJES..47.1159L. doi:10.1139/E10-005.
- ^ Charles R. Eastman (1894). "Beiträge zur Kenntniss der Gattung Oxyrhina: mit besonderer Berücksichtigung von Oxyrhina mantelli Agassiz" [Contributions to the knowledge of the genus Oxyrhina: with special reference to Oxyrhina mantelli Agassiz] (PDF). Palaeontographica (in German). 41: 149–191.
- ^ Mikael Siverson; David John Ward; Johan Lindgren; L. Scott Kelly (2013). "Mid-Cretaceous Cretoxyrhina (Elasmobranchii) from Mangyshlak, Kazakhstan and Texas, USA". Alcheringa: An Australasian Journal of Palaeontology. 37 (1): 1–18. Bibcode:2013Alch...37...87S. doi:10.1080/03115518.2012.709440. S2CID 129785545.
- ^ Phillip Sternes; Kenshu Shimada (2018), Caudal fin of the Late Cretaceous shark, Cretoxyrhina mantelli (Lamniformes: Cretoxyrhinidae), morphometrically compared to that of extant lamniform sharks, Society of Vertebrate Paleontology, archived (PDF) from the original on 2018-12-05, retrieved 2018-12-05
- ^ Michael G. Newbrey; Mikael Siversson; Todd D. Cook; Allison M. Fotheringham; Rebecca L. Sanchez (2015). "Vertebral Morphology, Dentition, Age, Growth, and Ecology of the Large Lamniform Shark Cardabiodon ricki". Acta Palaeontologica Polonica. 60 (4): 877–897. doi:10.4202/app.2012.0047.
- ^ Jacopo Amalfitano; Luca Giusberti; Eliana Fornaciari; Fabio Marco Dalla Vicchia; Valeria Luciani; Jürgen Kriwet; Giorgio Carnevale (2019). "Large deadfall of the 'ginsu' shark Cretoxyrhina mantelli (Agassiz, 1835) (Neoselachii, Lamniformes) from the Upper Cretaceous of northeastern Italy". Cretaceous Research. 98 (June 2019): 250–275. Bibcode:2019CrRes..98..250A. doi:10.1016/j.cretres.2019.02.003. hdl:11392/2402988. S2CID 135196193.
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