Carcharhiniformes (Ground Sharks)

Carcharhiniformes, the ground sharks, are the largest order of sharks. With over 270 species, Carcharhiniformes include a number of common types, such as catsharks, swellsharks, and the sandbar shark.
Members of this order are characterized by the presence of a nictitating membrane over the eye, two dorsal fins, an anal fin, and five gill slits.
The families in the order Carcharhiniformes are expected to be revised; recent DNA studies show that some of the conventional groups are not monophyletic.
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== Families ==
* Carcharhinidae
* Sphyrnidae