Taxon Description (Wikipedia)
The
ground sharks, order
Carcharhiniformes, are the largest order of sharks; they are also called
whaler sharks. With over 270 species, carcharhiniforms include a number of common types, such as the blue shark, catsharks, swellsharks, and sandbar shark.
Members of the orders are characterized by the presence of a nictitating membrane over the eye, two dorsal fins, an anal fin, and five gill slits.
The families of the carcharhiniforms are expected to be revised; recent DNA studies show that some of the traditional groups are not monophyletic.
full article at Wikipedia
