The order Hexanchiformes means "six arches" and comprises the most primitive species of sharks, which contain an extra pairs of gill slits. The genus Chlamydoselachus, meaning "frilled shark," is part of this order. Within the order Carcharhiniformes, from the Greek "jagged nose," the school shark is the only species of the genus Galeorhinus, which means "shark with nose," deriving from the Greek words galeos and rhinos. Also part of this order, hammerhead sharks are part of the genus Sphyrna, which means "hammer."
Also called lamnoids, the sharks in the order Lamniformes are named after the word "lamia," which was a serpent-like monster in Greek mythology. Part of this group, the great white shark (Carcharodon carcharias) has the scientific name meaning "sharp tooth." The whale shark, or Rhincodon typus, from the Greek, "rhyngchos" meaning snout and "odontos," which means tooth, is the best known species order Orectolobiformes, a group of sharks featuring colorful patterns. With the exception of the whale-shark, most Orectolobiformes species live in shallow water.
The genus Squatina is the only representative of the order Squatiniformes, which include sharks with flattened bodies resembling rays and skates. The word squatina derives from the Latin, meaning "a kind of shark." The order Heterodontiformes contain only one genus, Heterodontus, also known as bullhead sharks. The word Heterodontus comes from the Greek meaning "different tooth," and refers to the presence of molar-like rear teeth. The crested bullhead shark or Heterodontus galeatus has elevations above the eyes; the Latin word galeatus means "helmeted."
Pristiophoriformes includes saw sharks of the genera Pristiophorus, meaning "saw carrier" and Pliotrema, which is one of the few species out of the order Hexanchiformes with six pairs of gill slits. The name reflects this characteristic, as it comes from the Greek roots pleios, which means "more" and trema, which means "hole." The order Squaliformes include dog sharks, which have "short snouts," such as Isistius brasiliensis, first found in Brazil. Squalus is the largest genus, deriving form the Latin for shark.