4 Sharks: The Animal Answer Guide
Subdivision Selachii (sharks)
Superorder Squalomorphi
Order Hexanchiformes—two families of frill and cow
sharks
Order Squaliformes—six families of dogfish, gulper,
lantern, sleeper, and kitefin sharks
Order Pristiophoriformes—one family, saw sharks
Order Squatiniformes—one family, angel sharks
Order Echinorhiniformes—one family, bramble
sharks
Superorder Galeomorphi
Order Heterodontiformes—one family, bullhead and
horn sharks
Order Orectolobiformes—seven families of carpet,
bamboo, Zebra, nurse, and Whale sharks
Order Lamniformes—seven families of Sand Tiger,
Goblin, Megamouth, thresher, Basking, and
mackerel sharks
Order Carcharhiniformes—eight families of cat,
hound, requiem, and hammerhead sharks
Subdivision Batoidea (skates and rays)
Order Torpediniformes—two families of torpedo
electric rays
Order Pristiformes—one family, sawfishes
Order Rajiformes—four families of guitarfishes and
skates
Order Myliobatiformes—eleven families of stingrays,
butterfly rays, eagle and manta rays
Subclass Holocephali
Superorder Holocephalimorpha
Order Chimaeriformes—three families of chimaeras,
ratfishes, and ghostfishes
Differences among and between the various orders involve descriptions
of their anatomy, including number and placement of fins, presence of fin
spines, tooth number and characteristics, presence of a spiracle (modified
gill opening on the top of the head for taking water into the gills), type of
large intestine, number and position of gill slits, and presence of an eye-
lid—among other characteristics. A group-by-group breakdown requires
too much detail for the present discussion, although basic body parts used
in describing and distinguishing among species are shown in the illustra-
tion. One important anatomical feature that separates orders, families, and
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