Chondrichthyes
Carcharhiniformes There are eight families in this order.  It is the largest order, containing almost 200 species.  They are commonly referred to as the groundsharks, and some of the species include the blue, tiger, bull, reef and oceanic whitetip sharks (collectively called the requiem sharks) along with the houndsharks, catsharks and hammerhead sharks.  They are distinguished by an elongated snout and a nictitating membrane which protects the eyes during an attack.