| Isistius Temporal range: 56–0 Ma[1] Thanetian to Present |
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|---|---|
| Cookiecutter shark (I. brasiliensis) | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Elasmobranchii |
| Order: | Squaliformes |
| Family: | Dalatiidae |
| Genus: | Isistius T. N. Gill, 1865 |
| Type species | |
| Isistius brasiliensis (Quoy & Gaimard, 1824) |
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Isistius is a genus of dogfish sharks in the family Dalatiidae. They are commonly known as cookiecutter sharks. Members of the genus are known for their unusual behaviour and dentition.[2]
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The cookiecutter sharks, or 'cigar sharks' are noted as a genus of sharks that are unusual in the manner in which they replace their teeth. Instead of replacing teeth singly as they get damaged or lost, for example in hunting, such sharks replace the whole set. They can repeat such replacement throughout their lifetime.[3]
Cookiecutter sharks often attack large shoals of fish, but have been known to circle fishing vessels in order to get an easy meal. It is particularly notorious for biting small chunks off of a prey animal in passing. Large prey such as swordfish and cetaceans, may bear several healed wounds from such bites.[4]
Weaker prey may be injured enough to be weakened until they are unable to swim properly. They then are prone to sinking, enabling the Isistius to gorge. Isistius species can eat half of their own body weight at a time and are found in oceanic waters.
In unusual circumstances, cookiecutter sharks have been known to attack humans if they find them in their hunting grounds, and there even have been reports of of their killing humans, circling them in great numbers while stripping their flesh.