Cretoxyrhina

A Cretoxyrhina attacks a small mosasaur, breaching the surface.

***Cretoxyrhina mantelli*** was a large shark belonging to the Cretoxyrhinidae that lived about 100 to 82 million years ago, during the late Cretaceous period. It is nicknamed the **Ginsu shark** in reference to the Ginsu knife, since it fed by slicing into its victims with its knife-sharp teeth. It had no common name in the early literature, although over 30 synonyms were assigned to it. Its genus name is *creto-* (for "Cretaceous") prefixed to *Oxyrhina* ("sharp-nosed"), its original name.

## Description

*Cretoxyrhina* is among the most well-understood fossil sharks to date. Several preserved specimens have revealed a great deal of insight about the physical features and lifestyle of this ancient predatory shark.

The fossil teeth of *C. mantelli* are up to 7 cm long, curved, and smooth-edged, with a thick enamel coating. The jaws of *Cretoxyrhina* contained up to seven rows of teeth, with 34 teeth in each row of its upper jaw and 36 in each row of its lower jaw.

*Cretoxyrhina mantelli* grew up to 7-9 metres (23-30 ft) long, and exceeded its distant relative, the extant great white shark, *Carcharodon carharias*, in size.

## Discovery

This shark was first identified by the famous Swiss Naturalist Louis Agassiz, in 1843, as *Cretoxyhrina mantelli*. However, the most complete specimen of this shark was discovered in 1890, by the fossil hunter Charles H. Sternberg, who published his findings in 1907. The specimen comprised a nearly complete associated vertebral column and over 250 associated teeth. This kind of exceptional preservation of fossil sharks is rare, because a shark's skeleton is made of cartilage, which is not prone to fossilization, and often decays quickly due to scavenging and exposure to the elements. Charles dubbed the specimen *Oxyrhina mantelli*. This specimen represented a 20-foot-long (6.1 m) shark. It was excavated from Hackberry Creek, Gove County, Kansas.

In later years, several other specimens have also been found. One such specimen was discovered in 1891 by George Sternberg, and was stored in a Munich museum. This specimen was also reported to be 20 feet long, but was destroyed during a bombing raid on Munich in World War II.

## Paleobiology and Paleoecology

*Cretoxyrhina* was the largest shark in its time and was among the chief predators of the seas. Fossil records revealed that it preyed on a variety of marine animals, such as marine reptiles including mosasaurs like *Tylosaurus*, plesiosaurs like *Elasmosaurus*, bony fish like *Xiphactinus*, and protostegid turtles like *Archelon*. Some finds include regurgitated remains, such as those of a small section of mosasaur spinal column that were partially digested before being evicted from the shark's stomach. Cretoxyrhina may have also hunted the pterosaur *Pteranodon*, as a tooth was found embedded in the bone of one of these giant pterosaurs. Whether *Cretoxyrhina* was scavenging the pterosaur or actively hunted it is not known.

This shark lived in Cenomanian–Campanian seas worldwide, including in the Western Interior Seaway of North America. The reason for its extinction remains unknown, but may in part be due to the appearance of assorted genera of large mosasaurs, which may well have preyed upon *Cretoxyrhina*.

## In Popular Culture

Cretoxyrhina makes an appearance as a major predator of the plesiosaur *Dolichorynchops* in the IMAX film *Sea Monsters: A Prehistoric Adventure* and its associated video game. It also appears as a primary competitor and predator of mosasaurs in the Discovery Channel Miniseries *Monsters Resurrected*, in the episode *T. rex of the Deep*. In said episode, it is said that mosasaurs hunted the *Cretoxyrhina* to extinction, but in reality, it is unlikely that predation alone was a cause for this shark's extinction.