Species Name
The species that is going to be examined is Cretoxyrhina mantelli or more commonly known as the Ginsu shark.
Class = Chondrichthyes
Order = Lamniformes
Family = Cretoxyrhinidae
Genus = Cretoxyrhina
Species = Cretoxyrhina mantelli
The binomial taxonomic names of Cretoxyrhina mantelli from Class to Species is listed above (Amalfitano et al. 2018).
Locality/Material
There has been evidence and fossils found throughout the world including: the Midwest United States, Africa, Asia, Europe and more places (Amalfitano et al 2018). Fossils have specifically been found in Kansas, which used to be the Western Interior Sea, and Northern Italy (Amalfitano et al 2018)(Bourdon and Everhart 2011). The fossils found in Northern Italy are most commonly reported as teeth, however some partial skeletons have been recovered with regard to Cretoxyrhina mantelli (Amalfitano et al 2018).
Distribution
Cretoxyrhina mantelli could be located throughout the world in the Late Cretaceous Period approximately 100 – 60 million years ago (Shimada 1997). Due to the fact that Cretoxyrhina mantelli is a shark, the majority of its endoskeleton is made of cartilage and so fossilization would not occur. However, certain aspects of Cretoxyrhina mantelli could be fossilized with the lots of fossilized teeth being found (Bourdon and Everhart 2011). One of the main locations that fossilized Cretoxyrhina mantelli teeth have been found has been in the Midwest of the United States which used to be the Western Interior Sea (Bourdon and Everhart 2011). One believed local habitat in the Midwest was found to be in Kansas due to fossilized teeth being found.
Ecological and Biological Information
Age
Cretoxyrhina mantelli lived between 100 – 60 million years ago during the Late Cretaceous period (Shimada 1997). The von Bertalanffy growth function allows estimates to be made regarding the estimated lifespan of Cretoxyrhina mantelli, with estimates suggesting the species could live to a maximum of 38 years (Shimada 2008).
Growth Rate
Cretoxyrhina mantelli, along with all other sharks, are born alive. However, Cretoxyrhina mantelli unlike other sharks was born unusually large. In addition to a large birth size, their early life is distinguished by rapid growth (Shimada 2008). This resulting large initial size and large initial growth rate would have been beneficial as it would have allowed Cretoxyrhina mantelli to feed on larger prey as well as deterring potential predators with its large size (Shimada 2008).
Size
Cretoxyrhina mantelli was estimated to have a maximum length of 7 metres in length, in comparison to Carcharodon carcharias (Great White Sharks) which grow to be 4 -5 metres on average but can grow larger depending on the gender (Hone et al. 2018). Additionally, it was estimated that individuals of Cretoxyrhina mantelli could weigh as much as 3,400 kilograms (Shimada 2008).
Diet
There was evidence to show that a Cretoxyrhina tooth was found inside a Pteranodon skeleton. This was important because it showed that Cretoxyrhina fed on Pteranodon’s. However, they could not accurately determine with the evidence provided whether Cretoxyrhina predated on Pteranodons or whether Cretoxyrhina scavenged Pteranodon’s (Hone et al. 2018). However, Pteranodons were not the only thing that Cretoxyrhina mantelli fed on. Cretoxyrhina mantelli’s prey also consisted of: Mosasaurs, Plesiosaurs and Teleosts. Cretoxyrhina mantelli was believed to be at the top of the food chain and was considered to be the one of the apex predators of its time (Shimada 1997).
Key Synapamorphies/Autapomorphies/Plesiomorphies
Cretoxyrhina mantelli have a synapomorphy which is related to their jaw and teeth. Cretoxyrhina mantelli show a strongly disjunct heterodonty in the anterior half of the upper jaw dentition (Siverson et al 2013). In addition to this there is a lamnoid tooth pattern which can be seen on Cretoxyrhina mantelli teeth (Siverson et al 2013).
Phylogenetic and Evolutionary Importance/Implications
The importance of Cretoxyrhina mantelli fossils, mostly teeth but also some partial skeletons. It allows scientists to begin to understand and learn what they were like 100 – 60 million years ago when they lived (Shimada 1997). With one specific find, where a Cretoxyrhina mantelli tooth was found inside a Pteranodon skeleton, it shows that these large sharks fed on Pteranodons. However, it is unknown if Cretoxyrhina mantelli hunted Pteranodon’s or scavenged dead ones (Hone et al. 2018).
Interesting Facts/Common Myths/Controversies
One interesting fact regarding the species, Cretoxyrhina mantelli, is that they contained hundreds of razor-sharp teeth which people compared to Ginsu knives. This comparison is how Cretoxyrhina mantelli received its nickname the “Ginsu Shark” (New Dinosaurs).
References
Amalfitano J, Giusberti L, Fornaciari E, Vecchia FMD, Luciani V, Kriwet J, Carnevale G. 2018. Large deadfalls of the ‘ginsu’ shark Cretoxyrhina mantelli (Agassiz, 1835) (Neoselachii, Lamniformes) from the Upper Cretaceous of northeastern Italy. ResearchGate. DOI: 10.1016/j.cretres.2019.02.003.
Bourdon J, Everhart MJ. 2011. Analysis of an associated Cretoxyrhina mantelli dentition from the late Cretaceous (Smoky Hill Chalk, Late Coniacian) of western Kansas. Transactions of the Kansas Academy of Sciences. 114(1-2): 15-32.
https://www-jstor-org.ezproxy.library.dal.ca/stable/41309622?seq=1#metadata_info_tab_contents
Hone DWE, Witton MP, Habib MB. 2018. Evidence for the Cretaceous shark Cretoxyrhina mantelli feeding on the pterosaur Pteranodon from the Niobrara Formation. PeerJ. 6: e6031 https://doi.org/10.7717/peerj.6031
New Dinosaurs. Unknown Date. Unknown author. https://www.newdinosaurs.com/cretoxyrhina/
Shimada K. 1997. Paleoecological relationships of the Late Cretaceous lamniform shark, Cretoxyrhina mantelli (Agassiz). Scopus. 71(5): 926-933.
Shimada K. 2005. Phylogeny of lamniform sharks (Chondrichthyes: Elasmobranchii) and the contribution of dental characters to lamniform systematics. Scopus. 9(1): 55-72.
Shimada K. 2008. Ontogenetic parameters and life history strategies of the Late Cretaceous lamniform shark, Cretoxyrhina mantelli, based on vertebral growth increments. Scopus. 28(1): 21-33.
Siverson M, Ward DJ, Lindgren J, Kelley LS. 2013. Mid – Cretaceous Cretoxyrhina (Elasmobranchii) from Mangyshlak, Kazakhstan and Texas, USA. ResearchGate. 37(1): 1 – 18. DOI: 10.1080/03115518.2012.709440.
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